From: Jinu Kim Date: Tue, 21 Jul 2026 10:35:12 +0000 (+0900) Subject: KVM: x86/mmu: Check all address spaces before skipping unsync X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2e8a2c1b03068d76782343446f1b2114ae2ee0bd;p=thirdparty%2Fkernel%2Fstable.git KVM: x86/mmu: Check all address spaces before skipping unsync mmu_try_to_unsync_pages() skips the shadow-page lookup when the supplied memslot allows a hugepage, because a shadow page would disallow hugepages. But hugepage metadata is per-address-space while shadow pages are shared across all address spaces. With SMM, the other address space can therefore have a shadow page even when the supplied memslot allows a hugepage. Check the corresponding memslot in the other address space before taking the fast path. Skip the shadow-page lookup only when all address spaces allow a hugepage. Fixes: b3ae3ceb5569 ("KVM: x86/mmu: KVM: x86/mmu: Skip unsync when large pages are allowed") Assisted-by: Codex:GPT-5 Signed-off-by: Jinu Kim [invert direction of the conditional. - Paolo] Message-ID: <20260721103512.2136240-3-kimjw04271234@gmail.com> Signed-off-by: Paolo Bonzini --- diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 22cf222d3033..66e69d2a41b3 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -722,6 +722,26 @@ static struct kvm_lpage_info *lpage_info_slot(gfn_t gfn, return &slot->arch.lpage_info[level - 2][idx]; } +static bool kvm_gfn_is_lpage_allowed(struct kvm *kvm, + const struct kvm_memory_slot *slot, + gfn_t gfn, int level) +{ + const struct kvm_memory_slot *other_slot; + + BUILD_BUG_ON(KVM_MAX_NR_ADDRESS_SPACES > 2); + + if (lpage_info_slot(gfn, slot, level)->disallow_lpage) + return false; + + if (kvm_arch_nr_memslot_as_ids(kvm) > 1) { + other_slot = __gfn_to_memslot(__kvm_memslots(kvm, slot->as_id ^ 1), gfn); + if (other_slot && lpage_info_slot(gfn, other_slot, level)->disallow_lpage) + return false; + } + + return true; +} + /* * The most significant bit in disallow_lpage tracks whether or not memory * attributes are mixed, i.e. not identical for all gfns at the current level. @@ -2968,7 +2988,7 @@ int mmu_try_to_unsync_pages(struct kvm *kvm, const struct kvm_memory_slot *slot, * write-protected (see above), thus if the gfn can be mapped with a * hugepage and isn't write-tracked, it can't have a shadow page. */ - if (!lpage_info_slot(gfn, slot, PG_LEVEL_2M)->disallow_lpage) + if (kvm_gfn_is_lpage_allowed(kvm, slot, gfn, PG_LEVEL_2M)) return 0; /*