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KVM: x86/mmu: Leverage vcpu->last_used_slot in tdp_mmu_map_handle_target_level

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The existing TDP MMU methods to handle dirty logging are vcpu-agnostic
since they can be driven by MMU notifiers and other non-vcpu-specific
events in addition to page faults. However this means that the TDP MMU
is not benefiting from the new vcpu->last_used_slot. Fix that by
introducing a tdp_mmu_map_set_spte_atomic() which is only called during
a TDP page fault and has access to the kvm_vcpu for fast slot lookups.

This improves "Populate memory time" in dirty_log_perf_test by 5%:

Command                         | Before           | After
------------------------------- | ---------------- | -------------
./dirty_log_perf_test -v64 -x64 | 5.472321072s     | 5.169832886s

Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20210804222844.1419481-5-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
David Matlack 2021-08-04 22:28:41 +00:00 committed by Paolo Bonzini
parent fe22ed827c
commit 081de470f1
1 changed files with 33 additions and 9 deletions
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42
arch/x86/kvm/mmu/tdp_mmu.c
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@ -542,15 +542,40 @@ static inline bool tdp_mmu_set_spte_atomic_no_dirty_log(struct kvm *kvm,
return true;
}
static inline bool tdp_mmu_set_spte_atomic(struct kvm *kvm,
struct tdp_iter *iter,
u64 new_spte)
/*
* tdp_mmu_map_set_spte_atomic - Set a leaf TDP MMU SPTE atomically to resolve a
* TDP page fault.
*
* @vcpu: The vcpu instance that took the TDP page fault.
* @iter: a tdp_iter instance currently on the SPTE that should be set
* @new_spte: The value the SPTE should be set to
*
* Returns: true if the SPTE was set, false if it was not. If false is returned,
* this function will have no side-effects.
*/
static inline bool tdp_mmu_map_set_spte_atomic(struct kvm_vcpu *vcpu,
struct tdp_iter *iter,
u64 new_spte)
{
struct kvm *kvm = vcpu->kvm;
if (!tdp_mmu_set_spte_atomic_no_dirty_log(kvm, iter, new_spte))
return false;
handle_changed_spte_dirty_log(kvm, iter->as_id, iter->gfn,
iter->old_spte, new_spte, iter->level);
/*
* Use kvm_vcpu_gfn_to_memslot() instead of going through
* handle_changed_spte_dirty_log() to leverage vcpu->last_used_slot.
*/
if (is_writable_pte(new_spte)) {
struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, iter->gfn);
if (slot && kvm_slot_dirty_track_enabled(slot)) {
/* Enforced by kvm_mmu_hugepage_adjust. */
WARN_ON_ONCE(iter->level > PG_LEVEL_4K);
mark_page_dirty_in_slot(kvm, slot, iter->gfn);
}
}
return true;
}
@ -563,7 +588,7 @@ static inline bool tdp_mmu_zap_spte_atomic(struct kvm *kvm,
* immediately installing a present entry in its place
* before the TLBs are flushed.
*/
if (!tdp_mmu_set_spte_atomic(kvm, iter, REMOVED_SPTE))
if (!tdp_mmu_set_spte_atomic_no_dirty_log(kvm, iter, REMOVED_SPTE))
return false;
kvm_flush_remote_tlbs_with_address(kvm, iter->gfn,
@ -931,7 +956,7 @@ static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu, int write,
if (new_spte == iter->old_spte)
ret = RET_PF_SPURIOUS;
else if (!tdp_mmu_set_spte_atomic(vcpu->kvm, iter, new_spte))
else if (!tdp_mmu_map_set_spte_atomic(vcpu, iter, new_spte))
return RET_PF_RETRY;
/*
@ -1035,8 +1060,7 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
new_spte = make_nonleaf_spte(child_pt,
!shadow_accessed_mask);
if (tdp_mmu_set_spte_atomic(vcpu->kvm, &iter,
new_spte)) {
if (tdp_mmu_set_spte_atomic_no_dirty_log(vcpu->kvm, &iter, new_spte)) {
tdp_mmu_link_page(vcpu->kvm, sp, true,
huge_page_disallowed &&
req_level >= iter.level);