On 12/10/21 12:18 PM, Brijesh Singh wrote:

On 12/10/21 1:12 PM, Dave Hansen wrote:

quoted

On 12/10/21 7:43 AM, Brijesh Singh wrote:

quoted

+/* AMD SEV Confidential computing blob structure */
+#define CC_BLOB_SEV_HDR_MAGIC	0x45444d41
+struct cc_blob_sev_info {
+	u32 magic;
+	u16 version;
+	u16 reserved;
+	u64 secrets_phys;
+	u32 secrets_len;
+	u64 cpuid_phys;
+	u32 cpuid_len;
+};

This is an ABI structure rather than some purely kernel construct, right?

This is ABI between the guest BIOS and Guest OS. It is defined in the OVMF.

https://github.com/tianocore/edk2/blob/master/OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h

SEV-SNP FW spec does not have it documented; it's up to the guest BIOS
on how it wants to communicate the Secrets and CPUID page location to
guest OS.

Well, no matter where it is defined, could we please make it a bit
easier for folks to find it in the future?

quoted

I searched through all of the specs to which you linked in the cover
letter.  I looked for "blob", "guid", the magic and part of the GUID
itself trying to find where this is defined to see if the struct is correct.

I couldn't find anything.

Where is the spec for this blob?  How large is it?  Did you mean to
leave a 4-byte hole after secrets_len and before cpuid_phys?

Yes, the length is never going to be > 4GB.

I was more concerned that this structure could change sizes if it were
compiled on 32-bit versus 64-bit code.  For kernel ABIs, we try not to
do that.

Is this somehow OK when talking to firmware?  Or can a 32-bit OS and
64-bit firmware never interact?