From 138f5f9cbe374ff87084f1d32181d2a4a2d924e8 Mon Sep 17 00:00:00 2001 From: Ackerley Tng Date: Fri, 22 May 2026 15:46:09 -0700 Subject: [PATCH] KVM: SEV: Unmap local kmaps in LIFO order, per highmem requirements Per highmem.h, local kernel mappings must be unmapped in the reserve order they were acquired, following a LIFO (last-in, first-out) stack-based approach, and that failure to do so "is invalid and causes malfunction". Swap the kunmap_local() calls in SNP post-populate flow to ensure the mappings are released in the correct order. Note, because SNP is 64-bit only, the bugs are benign as there are no highmem mappings to unwind. Fixes: 2a62345b3052 ("KVM: guest_memfd: GUP source pages prior to populating guest memory") Signed-off-by: Ackerley Tng Link: https://patch.msgid.link/20260522-fix-sev-gmem-post-populate-v2-4-3f196bfad5a1@google.com [sean: call out that the bug is benign] Signed-off-by: Sean Christopherson --- arch/x86/kvm/svm/sev.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index c73c028d72c1..0e7f8b5cd4cb 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -2347,8 +2347,8 @@ static int sev_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, memcpy(dst_vaddr, src_vaddr, PAGE_SIZE); - kunmap_local(src_vaddr); kunmap_local(dst_vaddr); + kunmap_local(src_vaddr); } ret = rmp_make_private(pfn, gfn << PAGE_SHIFT, PG_LEVEL_4K, @@ -2383,8 +2383,8 @@ static int sev_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, memcpy(src_vaddr, dst_vaddr, PAGE_SIZE); - kunmap_local(src_vaddr); kunmap_local(dst_vaddr); + kunmap_local(src_vaddr); } out: