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tools: fix handling of CPU family/model/stepping in SEV validation

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The SEV-ES boot measurement includes the initial CPU register state
(VMSA) and one of the fields includes the CPU identification. When
building a VMSA blob we get the CPU family/model/stepping from the
host capabilities, however, the VMSA must reflect the guest CPU not
host CPU. Thus using host capabilities is only when whe the guest
has the 'host-passthrough' CPU mode active. With 'host-model' it is
cannot be assumed host and guest match, because QEMU may not (yet)
have a named CPU model for a given host CPU.

Reviewed-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Erik Skultety <eskultet@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
This commit is contained in:
Daniel P. Berrangé 2023-08-25 09:32:25 +01:00
parent d40c6cad64
commit 6b95437c17
1 changed files with 5 additions and 0 deletions
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tools/virt-qemu-sev-validate
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@ -1054,6 +1054,11 @@ class LibvirtConfidentialVM(ConfidentialVM):
raise InsecureUsageException(
"Using CPU SKU from capabilities is not secure")
mode = doc.xpath("/domain/cpu/@mode")
if mode != "host-passthrough":
raise UnsupportedUsageException(
"Using CPU family/model/stepping from host not possible unless 'host-passthrough' is used")
sig = capsdoc.xpath("/capabilities/host/cpu/signature")
if len(sig) != 1:
raise UnsupportedUsageException(