Commit 0f38453cdb2e for kernel

commit 0f38453cdb2e17566ccb7c0f3dabd5bd21caca26
Author: Jinu Kim <kimjw04271234@gmail.com>
Date:   Tue Jul 21 19:35:11 2026 +0900

    KVM: x86/mmu: Check write tracking in all address spaces

    kvm_gfn_is_write_tracked() checks only the supplied memslot, but page
    tracking is per-address-space and shadow pages are shared across all
    address spaces.  With SMM, a GFN can therefore be write-tracked in one
    address space and appear untracked through the other.

    Check the supplied slot first, then the slot for the other address space.
    This ensures all callers honor write tracking regardless of the active
    address space.  In particular, it prevents mmu_try_to_unsync_pages() from
    marking an upper-level shadow page unsync and eventually triggering the
    BUG in pte_list_remove().

    Fixes: 699023e23965 ("KVM: x86: add SMM to the MMU role, support SMRAM address space")
    Assisted-by: Codex:GPT-5
    Signed-off-by: Jinu Kim <kimjw04271234@gmail.com>
    Message-ID: <20260721103512.2136240-2-kimjw04271234@gmail.com>
    [invert direction of the conditional. - Paolo]
    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/mmu/page_track.c b/arch/x86/kvm/mmu/page_track.c
index 1b17b12393a8..7e8195a311bb 100644
--- a/arch/x86/kvm/mmu/page_track.c
+++ b/arch/x86/kvm/mmu/page_track.c
@@ -130,13 +130,23 @@ void __kvm_write_track_remove_gfn(struct kvm *kvm,
 	kvm_mmu_gfn_allow_lpage(slot, gfn);
 }

-/*
- * check if the corresponding access on the specified guest page is tracked.
- */
+static bool __kvm_gfn_is_write_tracked(const struct kvm_memory_slot *slot,
+				       gfn_t gfn)
+{
+	int index;
+
+	if (!slot)
+		return false;
+
+	index = gfn_to_index(gfn, slot->base_gfn, PG_LEVEL_4K);
+	return !!READ_ONCE(slot->arch.gfn_write_track[index]);
+}
+
+/* check if write access is tracked on the specified guest page.  */
 bool kvm_gfn_is_write_tracked(struct kvm *kvm,
 			      const struct kvm_memory_slot *slot, gfn_t gfn)
 {
-	int index;
+	const struct kvm_memory_slot *other_slot;

 	if (!slot)
 		return false;
@@ -144,8 +154,18 @@ bool kvm_gfn_is_write_tracked(struct kvm *kvm,
 	if (!kvm_page_track_write_tracking_enabled(kvm))
 		return false;

-	index = gfn_to_index(gfn, slot->base_gfn, PG_LEVEL_4K);
-	return !!READ_ONCE(slot->arch.gfn_write_track[index]);
+	BUILD_BUG_ON(KVM_MAX_NR_ADDRESS_SPACES > 2);
+
+	if (__kvm_gfn_is_write_tracked(slot, gfn))
+		return true;
+
+	if (kvm_arch_nr_memslot_as_ids(kvm) > 1) {
+		other_slot = __gfn_to_memslot(__kvm_memslots(kvm, slot->as_id ^ 1), gfn);
+		if (__kvm_gfn_is_write_tracked(other_slot, gfn))
+			return true;
+	}
+
+	return false;
 }

 #ifdef CONFIG_KVM_EXTERNAL_WRITE_TRACKING