139 lines
4.3 KiB
C
139 lines
4.3 KiB
C
// 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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/*
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* SPTEs must be modified atomically if they are shadow-present, leaf
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* SPTEs, and have volatile bits, i.e. has bits that can be set outside
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* of mmu_lock. The Writable bit can be set by KVM's fast page fault
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* handler, and 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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static inline bool kvm_tdp_mmu_spte_need_atomic_write(u64 old_spte, int level)
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{
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return is_shadow_present_pte(old_spte) &&
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is_last_spte(old_spte, level) &&
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spte_has_volatile_bits(old_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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if (kvm_tdp_mmu_spte_need_atomic_write(old_spte, level))
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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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static inline u64 tdp_mmu_clear_spte_bits(tdp_ptep_t sptep, u64 old_spte,
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u64 mask, int level)
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{
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atomic64_t *sptep_atomic;
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if (kvm_tdp_mmu_spte_need_atomic_write(old_spte, level)) {
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sptep_atomic = (atomic64_t *)rcu_dereference(sptep);
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return (u64)atomic64_fetch_and(~mask, sptep_atomic);
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}
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__kvm_tdp_mmu_write_spte(sptep, old_spte & ~mask);
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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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