KVM: x86/mmu: Check all address spaces before skipping unsync

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 <kimjw04271234@gmail.com>
[invert direction of the conditional. - Paolo]
Message-ID: <20260721103512.2136240-3-kimjw04271234@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>