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KVM: SEV: Unmap local kmaps in LIFO order, per highmem requirements

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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: 2a62345b30 ("KVM: guest_memfd: GUP source pages prior to populating guest memory")
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
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 <seanjc@google.com>
This commit is contained in:
Ackerley Tng 2026-05-22 15:46:09 -07:00 committed by Sean Christopherson
parent f13e900599
commit 138f5f9cbe
1 changed files with 2 additions and 2 deletions
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4
arch/x86/kvm/svm/sev.c
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@ -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: