提交 088acd23 编写于 作者: S Sean Christopherson 提交者: Paolo Bonzini

KVM: x86/mmu: Avoid collision with !PRESENT SPTEs in TDP MMU lpage stats

Factor in whether or not the old/new SPTEs are shadow-present when
adjusting the large page stats in the TDP MMU.  A modified MMIO SPTE can
toggle the page size bit, as bit 7 is used to store the MMIO generation,
i.e. is_large_pte() can get a false positive when called on a MMIO SPTE.
Ditto for nuking SPTEs with REMOVED_SPTE, which sets bit 7 in its magic
value.

Opportunistically move the logic below the check to verify at least one
of the old/new SPTEs is shadow present.

Use is/was_leaf even though is/was_present would suffice.  The code
generation is roughly equivalent since all flags need to be computed
prior to the code in question, and using the *_leaf flags will minimize
the diff in a future enhancement to account all pages, i.e. will change
the check to "is_leaf != was_leaf".
Reviewed-by: NDavid Matlack <dmatlack@google.com>
Reviewed-by: NBen Gardon <bgardon@google.com>

Fixes: 1699f65c ("kvm/x86: Fix 'lpages' kvm stat for TDM MMU")
Cc: stable@vger.kernel.org
Signed-off-by: NSean Christopherson <seanjc@google.com>
Signed-off-by: NMingwei Zhang <mizhang@google.com>
Message-Id: <20210803044607.599629-3-mizhang@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
上级 4293ddb7
...@@ -412,6 +412,7 @@ static void __handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn, ...@@ -412,6 +412,7 @@ static void __handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
bool was_leaf = was_present && is_last_spte(old_spte, level); bool was_leaf = was_present && is_last_spte(old_spte, level);
bool is_leaf = is_present && is_last_spte(new_spte, level); bool is_leaf = is_present && is_last_spte(new_spte, level);
bool pfn_changed = spte_to_pfn(old_spte) != spte_to_pfn(new_spte); bool pfn_changed = spte_to_pfn(old_spte) != spte_to_pfn(new_spte);
bool was_large, is_large;
WARN_ON(level > PT64_ROOT_MAX_LEVEL); WARN_ON(level > PT64_ROOT_MAX_LEVEL);
WARN_ON(level < PG_LEVEL_4K); WARN_ON(level < PG_LEVEL_4K);
...@@ -445,13 +446,6 @@ static void __handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn, ...@@ -445,13 +446,6 @@ static void __handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
trace_kvm_tdp_mmu_spte_changed(as_id, gfn, level, old_spte, new_spte); trace_kvm_tdp_mmu_spte_changed(as_id, gfn, level, old_spte, new_spte);
if (is_large_pte(old_spte) != is_large_pte(new_spte)) {
if (is_large_pte(old_spte))
atomic64_sub(1, (atomic64_t*)&kvm->stat.lpages);
else
atomic64_add(1, (atomic64_t*)&kvm->stat.lpages);
}
/* /*
* The only times a SPTE should be changed from a non-present to * The only times a SPTE should be changed from a non-present to
* non-present state is when an MMIO entry is installed/modified/ * non-present state is when an MMIO entry is installed/modified/
...@@ -477,6 +471,18 @@ static void __handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn, ...@@ -477,6 +471,18 @@ static void __handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
return; return;
} }
/*
* Update large page stats if a large page is being zapped, created, or
* is replacing an existing shadow page.
*/
was_large = was_leaf && is_large_pte(old_spte);
is_large = is_leaf && is_large_pte(new_spte);
if (was_large != is_large) {
if (was_large)
atomic64_sub(1, (atomic64_t *)&kvm->stat.lpages);
else
atomic64_add(1, (atomic64_t *)&kvm->stat.lpages);
}
if (was_leaf && is_dirty_spte(old_spte) && if (was_leaf && is_dirty_spte(old_spte) &&
(!is_present || !is_dirty_spte(new_spte) || pfn_changed)) (!is_present || !is_dirty_spte(new_spte) || pfn_changed))
......
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