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118 lines
3.8 KiB
118 lines
3.8 KiB
// SPDX-License-Identifier: GPL-2.0 |
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#ifndef __KVM_X86_MMU_TDP_ITER_H |
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#define __KVM_X86_MMU_TDP_ITER_H |
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#include <linux/kvm_host.h> |
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#include "mmu.h" |
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#include "spte.h" |
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/* |
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* TDP MMU SPTEs are RCU protected to allow paging structures (non-leaf SPTEs) |
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* to be zapped while holding mmu_lock for read, and to allow TLB flushes to be |
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* batched without having to collect the list of zapped SPs. Flows that can |
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* remove SPs must service pending TLB flushes prior to dropping RCU protection. |
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*/ |
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static inline u64 kvm_tdp_mmu_read_spte(tdp_ptep_t sptep) |
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{ |
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return READ_ONCE(*rcu_dereference(sptep)); |
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} |
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static inline u64 kvm_tdp_mmu_write_spte_atomic(tdp_ptep_t sptep, u64 new_spte) |
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{ |
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return xchg(rcu_dereference(sptep), new_spte); |
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} |
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static inline void __kvm_tdp_mmu_write_spte(tdp_ptep_t sptep, u64 new_spte) |
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{ |
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WRITE_ONCE(*rcu_dereference(sptep), new_spte); |
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} |
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static inline u64 kvm_tdp_mmu_write_spte(tdp_ptep_t sptep, u64 old_spte, |
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u64 new_spte, int level) |
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{ |
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/* |
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* Atomically write the SPTE if it is a shadow-present, leaf SPTE with |
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* volatile bits, i.e. has bits that can be set outside of mmu_lock. |
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* The Writable bit can be set by KVM's fast page fault handler, and |
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* Accessed and Dirty bits can be set by the CPU. |
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* |
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* Note, non-leaf SPTEs do have Accessed bits and those bits are |
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* technically volatile, but KVM doesn't consume the Accessed bit of |
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* non-leaf SPTEs, i.e. KVM doesn't care if it clobbers the bit. This |
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* logic needs to be reassessed if KVM were to use non-leaf Accessed |
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* bits, e.g. to skip stepping down into child SPTEs when aging SPTEs. |
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*/ |
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if (is_shadow_present_pte(old_spte) && is_last_spte(old_spte, level) && |
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spte_has_volatile_bits(old_spte)) |
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return kvm_tdp_mmu_write_spte_atomic(sptep, new_spte); |
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__kvm_tdp_mmu_write_spte(sptep, new_spte); |
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return old_spte; |
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} |
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/* |
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* A TDP iterator performs a pre-order walk over a TDP paging structure. |
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*/ |
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struct tdp_iter { |
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/* |
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* The iterator will traverse the paging structure towards the mapping |
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* for this GFN. |
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*/ |
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gfn_t next_last_level_gfn; |
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/* |
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* The next_last_level_gfn at the time when the thread last |
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* yielded. Only yielding when the next_last_level_gfn != |
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* yielded_gfn helps ensure forward progress. |
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*/ |
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gfn_t yielded_gfn; |
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/* Pointers to the page tables traversed to reach the current SPTE */ |
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tdp_ptep_t pt_path[PT64_ROOT_MAX_LEVEL]; |
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/* A pointer to the current SPTE */ |
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tdp_ptep_t sptep; |
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/* The lowest GFN mapped by the current SPTE */ |
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gfn_t gfn; |
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/* The level of the root page given to the iterator */ |
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int root_level; |
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/* The lowest level the iterator should traverse to */ |
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int min_level; |
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/* The iterator's current level within the paging structure */ |
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int level; |
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/* The address space ID, i.e. SMM vs. regular. */ |
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int as_id; |
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/* A snapshot of the value at sptep */ |
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u64 old_spte; |
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/* |
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* Whether the iterator has a valid state. This will be false if the |
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* iterator walks off the end of the paging structure. |
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*/ |
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bool valid; |
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/* |
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* True if KVM dropped mmu_lock and yielded in the middle of a walk, in |
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* which case tdp_iter_next() needs to restart the walk at the root |
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* level instead of advancing to the next entry. |
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*/ |
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bool yielded; |
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}; |
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/* |
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* Iterates over every SPTE mapping the GFN range [start, end) in a |
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* preorder traversal. |
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*/ |
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#define for_each_tdp_pte_min_level(iter, root, min_level, start, end) \ |
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for (tdp_iter_start(&iter, root, min_level, start); \ |
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iter.valid && iter.gfn < end; \ |
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tdp_iter_next(&iter)) |
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#define for_each_tdp_pte(iter, root, start, end) \ |
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for_each_tdp_pte_min_level(iter, root, PG_LEVEL_4K, start, end) |
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tdp_ptep_t spte_to_child_pt(u64 pte, int level); |
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void tdp_iter_start(struct tdp_iter *iter, struct kvm_mmu_page *root, |
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int min_level, gfn_t next_last_level_gfn); |
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void tdp_iter_next(struct tdp_iter *iter); |
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void tdp_iter_restart(struct tdp_iter *iter); |
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#endif /* __KVM_X86_MMU_TDP_ITER_H */
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