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594 lines
14 KiB
594 lines
14 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Copyright (c) 2017-2019 Borislav Petkov, SUSE Labs. |
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*/ |
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#include <linux/mm.h> |
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#include <linux/gfp.h> |
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#include <linux/ras.h> |
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#include <linux/kernel.h> |
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#include <linux/workqueue.h> |
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#include <asm/mce.h> |
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#include "debugfs.h" |
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|
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/* |
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* RAS Correctable Errors Collector |
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* |
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* This is a simple gadget which collects correctable errors and counts their |
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* occurrence per physical page address. |
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* |
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* We've opted for possibly the simplest data structure to collect those - an |
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* array of the size of a memory page. It stores 512 u64's with the following |
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* structure: |
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* |
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* [63 ... PFN ... 12 | 11 ... generation ... 10 | 9 ... count ... 0] |
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* |
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* The generation in the two highest order bits is two bits which are set to 11b |
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* on every insertion. During the course of each entry's existence, the |
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* generation field gets decremented during spring cleaning to 10b, then 01b and |
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* then 00b. |
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* |
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* This way we're employing the natural numeric ordering to make sure that newly |
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* inserted/touched elements have higher 12-bit counts (which we've manufactured) |
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* and thus iterating over the array initially won't kick out those elements |
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* which were inserted last. |
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* |
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* Spring cleaning is what we do when we reach a certain number CLEAN_ELEMS of |
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* elements entered into the array, during which, we're decaying all elements. |
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* If, after decay, an element gets inserted again, its generation is set to 11b |
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* to make sure it has higher numerical count than other, older elements and |
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* thus emulate an LRU-like behavior when deleting elements to free up space |
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* in the page. |
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* |
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* When an element reaches it's max count of action_threshold, we try to poison |
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* it by assuming that errors triggered action_threshold times in a single page |
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* are excessive and that page shouldn't be used anymore. action_threshold is |
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* initialized to COUNT_MASK which is the maximum. |
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* |
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* That error event entry causes cec_add_elem() to return !0 value and thus |
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* signal to its callers to log the error. |
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* |
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* To the question why we've chosen a page and moving elements around with |
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* memmove(), it is because it is a very simple structure to handle and max data |
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* movement is 4K which on highly optimized modern CPUs is almost unnoticeable. |
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* We wanted to avoid the pointer traversal of more complex structures like a |
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* linked list or some sort of a balancing search tree. |
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* |
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* Deleting an element takes O(n) but since it is only a single page, it should |
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* be fast enough and it shouldn't happen all too often depending on error |
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* patterns. |
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*/ |
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#undef pr_fmt |
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#define pr_fmt(fmt) "RAS: " fmt |
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/* |
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* We use DECAY_BITS bits of PAGE_SHIFT bits for counting decay, i.e., how long |
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* elements have stayed in the array without having been accessed again. |
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*/ |
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#define DECAY_BITS 2 |
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#define DECAY_MASK ((1ULL << DECAY_BITS) - 1) |
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#define MAX_ELEMS (PAGE_SIZE / sizeof(u64)) |
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/* |
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* Threshold amount of inserted elements after which we start spring |
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* cleaning. |
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*/ |
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#define CLEAN_ELEMS (MAX_ELEMS >> DECAY_BITS) |
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/* Bits which count the number of errors happened in this 4K page. */ |
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#define COUNT_BITS (PAGE_SHIFT - DECAY_BITS) |
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#define COUNT_MASK ((1ULL << COUNT_BITS) - 1) |
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#define FULL_COUNT_MASK (PAGE_SIZE - 1) |
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/* |
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* u64: [ 63 ... 12 | DECAY_BITS | COUNT_BITS ] |
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*/ |
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#define PFN(e) ((e) >> PAGE_SHIFT) |
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#define DECAY(e) (((e) >> COUNT_BITS) & DECAY_MASK) |
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#define COUNT(e) ((unsigned int)(e) & COUNT_MASK) |
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#define FULL_COUNT(e) ((e) & (PAGE_SIZE - 1)) |
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static struct ce_array { |
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u64 *array; /* container page */ |
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unsigned int n; /* number of elements in the array */ |
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unsigned int decay_count; /* |
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* number of element insertions/increments |
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* since the last spring cleaning. |
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*/ |
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u64 pfns_poisoned; /* |
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* number of PFNs which got poisoned. |
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*/ |
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u64 ces_entered; /* |
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* The number of correctable errors |
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* entered into the collector. |
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*/ |
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u64 decays_done; /* |
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* Times we did spring cleaning. |
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*/ |
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union { |
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struct { |
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__u32 disabled : 1, /* cmdline disabled */ |
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__resv : 31; |
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}; |
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__u32 flags; |
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}; |
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} ce_arr; |
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static DEFINE_MUTEX(ce_mutex); |
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static u64 dfs_pfn; |
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/* Amount of errors after which we offline */ |
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static u64 action_threshold = COUNT_MASK; |
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/* Each element "decays" each decay_interval which is 24hrs by default. */ |
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#define CEC_DECAY_DEFAULT_INTERVAL 24 * 60 * 60 /* 24 hrs */ |
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#define CEC_DECAY_MIN_INTERVAL 1 * 60 * 60 /* 1h */ |
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#define CEC_DECAY_MAX_INTERVAL 30 * 24 * 60 * 60 /* one month */ |
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static struct delayed_work cec_work; |
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static u64 decay_interval = CEC_DECAY_DEFAULT_INTERVAL; |
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/* |
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* Decrement decay value. We're using DECAY_BITS bits to denote decay of an |
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* element in the array. On insertion and any access, it gets reset to max. |
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*/ |
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static void do_spring_cleaning(struct ce_array *ca) |
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{ |
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int i; |
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for (i = 0; i < ca->n; i++) { |
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u8 decay = DECAY(ca->array[i]); |
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if (!decay) |
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continue; |
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decay--; |
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ca->array[i] &= ~(DECAY_MASK << COUNT_BITS); |
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ca->array[i] |= (decay << COUNT_BITS); |
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} |
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ca->decay_count = 0; |
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ca->decays_done++; |
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} |
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/* |
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* @interval in seconds |
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*/ |
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static void cec_mod_work(unsigned long interval) |
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{ |
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unsigned long iv; |
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iv = interval * HZ; |
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mod_delayed_work(system_wq, &cec_work, round_jiffies(iv)); |
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} |
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static void cec_work_fn(struct work_struct *work) |
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{ |
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mutex_lock(&ce_mutex); |
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do_spring_cleaning(&ce_arr); |
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mutex_unlock(&ce_mutex); |
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cec_mod_work(decay_interval); |
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} |
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/* |
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* @to: index of the smallest element which is >= then @pfn. |
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* |
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* Return the index of the pfn if found, otherwise negative value. |
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*/ |
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static int __find_elem(struct ce_array *ca, u64 pfn, unsigned int *to) |
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{ |
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int min = 0, max = ca->n - 1; |
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u64 this_pfn; |
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while (min <= max) { |
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int i = (min + max) >> 1; |
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this_pfn = PFN(ca->array[i]); |
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if (this_pfn < pfn) |
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min = i + 1; |
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else if (this_pfn > pfn) |
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max = i - 1; |
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else if (this_pfn == pfn) { |
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if (to) |
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*to = i; |
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return i; |
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} |
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} |
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/* |
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* When the loop terminates without finding @pfn, min has the index of |
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* the element slot where the new @pfn should be inserted. The loop |
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* terminates when min > max, which means the min index points to the |
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* bigger element while the max index to the smaller element, in-between |
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* which the new @pfn belongs to. |
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* |
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* For more details, see exercise 1, Section 6.2.1 in TAOCP, vol. 3. |
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*/ |
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if (to) |
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*to = min; |
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return -ENOKEY; |
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} |
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static int find_elem(struct ce_array *ca, u64 pfn, unsigned int *to) |
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{ |
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WARN_ON(!to); |
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if (!ca->n) { |
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*to = 0; |
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return -ENOKEY; |
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} |
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return __find_elem(ca, pfn, to); |
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} |
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static void del_elem(struct ce_array *ca, int idx) |
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{ |
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/* Save us a function call when deleting the last element. */ |
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if (ca->n - (idx + 1)) |
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memmove((void *)&ca->array[idx], |
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(void *)&ca->array[idx + 1], |
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(ca->n - (idx + 1)) * sizeof(u64)); |
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ca->n--; |
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} |
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static u64 del_lru_elem_unlocked(struct ce_array *ca) |
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{ |
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unsigned int min = FULL_COUNT_MASK; |
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int i, min_idx = 0; |
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for (i = 0; i < ca->n; i++) { |
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unsigned int this = FULL_COUNT(ca->array[i]); |
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if (min > this) { |
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min = this; |
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min_idx = i; |
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} |
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} |
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del_elem(ca, min_idx); |
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return PFN(ca->array[min_idx]); |
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} |
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/* |
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* We return the 0th pfn in the error case under the assumption that it cannot |
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* be poisoned and excessive CEs in there are a serious deal anyway. |
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*/ |
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static u64 __maybe_unused del_lru_elem(void) |
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{ |
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struct ce_array *ca = &ce_arr; |
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u64 pfn; |
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if (!ca->n) |
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return 0; |
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mutex_lock(&ce_mutex); |
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pfn = del_lru_elem_unlocked(ca); |
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mutex_unlock(&ce_mutex); |
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return pfn; |
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} |
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static bool sanity_check(struct ce_array *ca) |
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{ |
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bool ret = false; |
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u64 prev = 0; |
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int i; |
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for (i = 0; i < ca->n; i++) { |
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u64 this = PFN(ca->array[i]); |
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if (WARN(prev > this, "prev: 0x%016llx <-> this: 0x%016llx\n", prev, this)) |
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ret = true; |
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prev = this; |
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} |
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if (!ret) |
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return ret; |
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pr_info("Sanity check dump:\n{ n: %d\n", ca->n); |
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for (i = 0; i < ca->n; i++) { |
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u64 this = PFN(ca->array[i]); |
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pr_info(" %03d: [%016llx|%03llx]\n", i, this, FULL_COUNT(ca->array[i])); |
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} |
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pr_info("}\n"); |
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return ret; |
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} |
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/** |
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* cec_add_elem - Add an element to the CEC array. |
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* @pfn: page frame number to insert |
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* |
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* Return values: |
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* - <0: on error |
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* - 0: on success |
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* - >0: when the inserted pfn was offlined |
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*/ |
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static int cec_add_elem(u64 pfn) |
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{ |
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struct ce_array *ca = &ce_arr; |
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int count, err, ret = 0; |
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unsigned int to = 0; |
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/* |
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* We can be called very early on the identify_cpu() path where we are |
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* not initialized yet. We ignore the error for simplicity. |
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*/ |
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if (!ce_arr.array || ce_arr.disabled) |
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return -ENODEV; |
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mutex_lock(&ce_mutex); |
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ca->ces_entered++; |
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/* Array full, free the LRU slot. */ |
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if (ca->n == MAX_ELEMS) |
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WARN_ON(!del_lru_elem_unlocked(ca)); |
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err = find_elem(ca, pfn, &to); |
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if (err < 0) { |
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/* |
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* Shift range [to-end] to make room for one more element. |
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*/ |
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memmove((void *)&ca->array[to + 1], |
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(void *)&ca->array[to], |
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(ca->n - to) * sizeof(u64)); |
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ca->array[to] = pfn << PAGE_SHIFT; |
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ca->n++; |
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} |
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/* Add/refresh element generation and increment count */ |
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ca->array[to] |= DECAY_MASK << COUNT_BITS; |
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ca->array[to]++; |
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/* Check action threshold and soft-offline, if reached. */ |
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count = COUNT(ca->array[to]); |
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if (count >= action_threshold) { |
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u64 pfn = ca->array[to] >> PAGE_SHIFT; |
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if (!pfn_valid(pfn)) { |
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pr_warn("CEC: Invalid pfn: 0x%llx\n", pfn); |
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} else { |
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/* We have reached max count for this page, soft-offline it. */ |
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pr_err("Soft-offlining pfn: 0x%llx\n", pfn); |
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memory_failure_queue(pfn, MF_SOFT_OFFLINE); |
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ca->pfns_poisoned++; |
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} |
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del_elem(ca, to); |
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/* |
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* Return a >0 value to callers, to denote that we've reached |
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* the offlining threshold. |
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*/ |
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ret = 1; |
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goto unlock; |
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} |
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ca->decay_count++; |
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if (ca->decay_count >= CLEAN_ELEMS) |
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do_spring_cleaning(ca); |
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WARN_ON_ONCE(sanity_check(ca)); |
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unlock: |
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mutex_unlock(&ce_mutex); |
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return ret; |
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} |
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static int u64_get(void *data, u64 *val) |
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{ |
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*val = *(u64 *)data; |
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return 0; |
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} |
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static int pfn_set(void *data, u64 val) |
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{ |
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*(u64 *)data = val; |
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cec_add_elem(val); |
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return 0; |
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} |
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DEFINE_DEBUGFS_ATTRIBUTE(pfn_ops, u64_get, pfn_set, "0x%llx\n"); |
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static int decay_interval_set(void *data, u64 val) |
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{ |
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if (val < CEC_DECAY_MIN_INTERVAL) |
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return -EINVAL; |
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if (val > CEC_DECAY_MAX_INTERVAL) |
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return -EINVAL; |
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*(u64 *)data = val; |
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decay_interval = val; |
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cec_mod_work(decay_interval); |
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return 0; |
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} |
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DEFINE_DEBUGFS_ATTRIBUTE(decay_interval_ops, u64_get, decay_interval_set, "%lld\n"); |
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static int action_threshold_set(void *data, u64 val) |
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{ |
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*(u64 *)data = val; |
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if (val > COUNT_MASK) |
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val = COUNT_MASK; |
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action_threshold = val; |
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return 0; |
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} |
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DEFINE_DEBUGFS_ATTRIBUTE(action_threshold_ops, u64_get, action_threshold_set, "%lld\n"); |
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static const char * const bins[] = { "00", "01", "10", "11" }; |
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static int array_show(struct seq_file *m, void *v) |
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{ |
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struct ce_array *ca = &ce_arr; |
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int i; |
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mutex_lock(&ce_mutex); |
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seq_printf(m, "{ n: %d\n", ca->n); |
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for (i = 0; i < ca->n; i++) { |
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u64 this = PFN(ca->array[i]); |
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seq_printf(m, " %3d: [%016llx|%s|%03llx]\n", |
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i, this, bins[DECAY(ca->array[i])], COUNT(ca->array[i])); |
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} |
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seq_printf(m, "}\n"); |
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seq_printf(m, "Stats:\nCEs: %llu\nofflined pages: %llu\n", |
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ca->ces_entered, ca->pfns_poisoned); |
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seq_printf(m, "Flags: 0x%x\n", ca->flags); |
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seq_printf(m, "Decay interval: %lld seconds\n", decay_interval); |
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seq_printf(m, "Decays: %lld\n", ca->decays_done); |
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seq_printf(m, "Action threshold: %lld\n", action_threshold); |
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mutex_unlock(&ce_mutex); |
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return 0; |
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} |
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DEFINE_SHOW_ATTRIBUTE(array); |
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static int __init create_debugfs_nodes(void) |
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{ |
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struct dentry *d, *pfn, *decay, *count, *array; |
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d = debugfs_create_dir("cec", ras_debugfs_dir); |
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if (!d) { |
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pr_warn("Error creating cec debugfs node!\n"); |
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return -1; |
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} |
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decay = debugfs_create_file("decay_interval", S_IRUSR | S_IWUSR, d, |
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&decay_interval, &decay_interval_ops); |
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if (!decay) { |
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pr_warn("Error creating decay_interval debugfs node!\n"); |
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goto err; |
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} |
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count = debugfs_create_file("action_threshold", S_IRUSR | S_IWUSR, d, |
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&action_threshold, &action_threshold_ops); |
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if (!count) { |
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pr_warn("Error creating action_threshold debugfs node!\n"); |
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goto err; |
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} |
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if (!IS_ENABLED(CONFIG_RAS_CEC_DEBUG)) |
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return 0; |
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pfn = debugfs_create_file("pfn", S_IRUSR | S_IWUSR, d, &dfs_pfn, &pfn_ops); |
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if (!pfn) { |
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pr_warn("Error creating pfn debugfs node!\n"); |
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goto err; |
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} |
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array = debugfs_create_file("array", S_IRUSR, d, NULL, &array_fops); |
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if (!array) { |
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pr_warn("Error creating array debugfs node!\n"); |
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goto err; |
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} |
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return 0; |
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err: |
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debugfs_remove_recursive(d); |
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return 1; |
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} |
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static int cec_notifier(struct notifier_block *nb, unsigned long val, |
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void *data) |
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{ |
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struct mce *m = (struct mce *)data; |
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if (!m) |
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return NOTIFY_DONE; |
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/* We eat only correctable DRAM errors with usable addresses. */ |
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if (mce_is_memory_error(m) && |
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mce_is_correctable(m) && |
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mce_usable_address(m)) { |
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if (!cec_add_elem(m->addr >> PAGE_SHIFT)) { |
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m->kflags |= MCE_HANDLED_CEC; |
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return NOTIFY_OK; |
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} |
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} |
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return NOTIFY_DONE; |
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} |
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static struct notifier_block cec_nb = { |
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.notifier_call = cec_notifier, |
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.priority = MCE_PRIO_CEC, |
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}; |
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static int __init cec_init(void) |
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{ |
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if (ce_arr.disabled) |
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return -ENODEV; |
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ce_arr.array = (void *)get_zeroed_page(GFP_KERNEL); |
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if (!ce_arr.array) { |
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pr_err("Error allocating CE array page!\n"); |
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return -ENOMEM; |
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} |
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if (create_debugfs_nodes()) { |
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free_page((unsigned long)ce_arr.array); |
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return -ENOMEM; |
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} |
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INIT_DELAYED_WORK(&cec_work, cec_work_fn); |
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schedule_delayed_work(&cec_work, CEC_DECAY_DEFAULT_INTERVAL); |
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mce_register_decode_chain(&cec_nb); |
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pr_info("Correctable Errors collector initialized.\n"); |
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return 0; |
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} |
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late_initcall(cec_init); |
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int __init parse_cec_param(char *str) |
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{ |
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if (!str) |
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return 0; |
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if (*str == '=') |
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str++; |
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|
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if (!strcmp(str, "cec_disable")) |
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ce_arr.disabled = 1; |
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else |
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return 0; |
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return 1; |
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}
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