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i386/sev: Allow measured direct kernel boot on SNP

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In SNP, the hashes page designated with a specific metadata entry
published in AmdSev OVMF.

Therefore, if the user enabled kernel hashes (for measured direct boot),
QEMU should prepare the content of hashes table, and during the
processing of the metadata entry it copy the content into the designated
page and encrypt it.

Note that in SNP (unlike SEV and SEV-ES) the measurements is done in
whole 4KB pages.  Therefore QEMU zeros the whole page that includes the
hashes table, and fills in the kernel hashes area in that page, and then
encrypts the whole page.  The rest of the page is reserved for SEV
launch secrets which are not usable anyway on SNP.

If the user disabled kernel hashes, QEMU pre-validates the kernel hashes
page as a zero page.

Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Pankaj Gupta <pankaj.gupta@amd.com>
Message-ID: <20240530111643.1091816-24-pankaj.gupta@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Dov Murik 2024-05-30 06:16:35 -05:00 • committed by Paolo Bonzini
parent cc483bf911
commit c1996992cc
2 changed files with 86 additions and 29 deletions
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2
include/hw/i386/pc.h
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@ -172,6 +172,8 @@ typedef enum {
SEV_DESC_TYPE_SNP_SECRETS,
/* The section contains address that can be used as a CPUID page */
SEV_DESC_TYPE_CPUID,
/* The section contains the region for kernel hashes for measured direct boot */
SEV_DESC_TYPE_SNP_KERNEL_HASHES = 0x10,
} ovmf_sev_metadata_desc_type;