virt: vmgenid: remap memory as decrypted

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It was found that AWS SEV-SNP enabled instances are not able to boot with
commit 81256a50aa ("x86/mm: Make memremap(MEMREMAP_WB) map memory as
encrypted by default") applied and the reason seems to be the vmgenid
device which requires unencrypted writeable memory.

A similar problem was previously fixed in DRM with commit
7dfede7d7e ("drm/vmwgfx: Fix guests running with TDX/SEV").

Note, trusting vmgenid device in a Confidential VM is questionable: the
malicious host may intentionally avoid notifying the guest when a copy is
created.

Fixes: 81256a50aa ("x86/mm: Make memremap(MEMREMAP_WB) map memory as encrypted by default")
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: stable@vger.kernel.org # 6.15+
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

...

This commit is contained in:

Vitaly Kuznetsov 2025-12-22 15:46:46 +01:00 • committed by Jason A. Donenfeld

parent cee9395acd

commit 1b48c13075

1 changed files with 2 additions and 1 deletions

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drivers/virt/vmgenid.c

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