From: Sean Christopherson seanjc@google.com
commit 088acd23526647844aec1c39db4ad02552c86c7b upstream.
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: David Matlack dmatlack@google.com Reviewed-by: Ben Gardon bgardon@google.com
Fixes: 1699f65c8b65 ("kvm/x86: Fix 'lpages' kvm stat for TDM MMU") Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson seanjc@google.com Signed-off-by: Mingwei Zhang mizhang@google.com Message-Id: 20210803044607.599629-3-mizhang@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kvm/mmu/tdp_mmu.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-)
--- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -410,6 +410,7 @@ static void __handle_changed_spte(struct bool was_leaf = was_present && is_last_spte(old_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 was_large, is_large;
WARN_ON(level > PT64_ROOT_MAX_LEVEL); WARN_ON(level < PG_LEVEL_4K); @@ -443,13 +444,6 @@ static void __handle_changed_spte(struct
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 * non-present state is when an MMIO entry is installed/modified/ @@ -475,6 +469,18 @@ static void __handle_changed_spte(struct 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) && (!is_present || !is_dirty_spte(new_spte) || pfn_changed))