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KVM: x86/mmu: Coalesce TDP MMU TLB flushes when zapping collapsible SPTEs

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When zapping collapsible SPTEs across multiple roots, gather pending
flushes and perform a single remote TLB flush at the end, as opposed to
flushing after processing every root.

Note, flush may be cleared by the result of zap_collapsible_spte_range().
This is intended and correct, e.g. yielding may have serviced a prior
pending flush.

Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210326021957.1424875-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson
2021-03-25 19:19:40 -07:00
committed by Paolo Bonzini
parent c28fa560c5
commit af95b53e56
1 changed files with 13 additions and 9 deletions
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22
arch/x86/kvm/mmu/tdp_mmu.c
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@ -1268,21 +1268,21 @@ void kvm_tdp_mmu_clear_dirty_pt_masked(struct kvm *kvm,
* Clear leaf entries which could be replaced by large mappings, for
* GFNs within the slot.
*/
static void zap_collapsible_spte_range(struct kvm *kvm,
static bool zap_collapsible_spte_range(struct kvm *kvm,
struct kvm_mmu_page *root,
struct kvm_memory_slot *slot)
struct kvm_memory_slot *slot,
bool flush)
{
gfn_t start = slot->base_gfn;
gfn_t end = start + slot->npages;
struct tdp_iter iter;
kvm_pfn_t pfn;
bool spte_set = false;
rcu_read_lock();
tdp_root_for_each_pte(iter, root, start, end) {
if (tdp_mmu_iter_cond_resched(kvm, &iter, spte_set)) {
spte_set = false;
if (tdp_mmu_iter_cond_resched(kvm, &iter, flush)) {
flush = false;
continue;
}
@ -1298,12 +1298,12 @@ static void zap_collapsible_spte_range(struct kvm *kvm,
tdp_mmu_set_spte(kvm, &iter, 0);
spte_set = true;
flush = true;
}
rcu_read_unlock();
if (spte_set)
kvm_flush_remote_tlbs(kvm);
return flush;
}
/*
@ -1314,6 +1314,7 @@ void kvm_tdp_mmu_zap_collapsible_sptes(struct kvm *kvm,
struct kvm_memory_slot *slot)
{
struct kvm_mmu_page *root;
bool flush = false;
int root_as_id;
for_each_tdp_mmu_root_yield_safe(kvm, root) {
@ -1321,8 +1322,11 @@ void kvm_tdp_mmu_zap_collapsible_sptes(struct kvm *kvm,
if (root_as_id != slot->as_id)
continue;
zap_collapsible_spte_range(kvm, root, slot);
flush = zap_collapsible_spte_range(kvm, root, slot, flush);
}
if (flush)
kvm_flush_remote_tlbs(kvm);
}
/*