diff options
| author | Tom Lendacky <thomas.lendacky@amd.com> | 2025-09-10 17:19:28 +0200 |
|---|---|---|
| committer | Borislav Petkov (AMD) <bp@alien8.de> | 2025-09-10 17:23:24 +0200 |
| commit | 8d73829b78ca1a0e6eb93380f3bf5193d58c281c (patch) | |
| tree | 699586c813538ac9da8690d3aceb2287b9a451d1 | |
| parent | 26a9f90b6101ea2c9d6f02802cf6d85108104b90 (diff) | |
x86/startup/sev: Document the CPUID flow in the boot #VC handler
Document the CPUID reading the different SEV guest types do - the SNP
one which relies on the presence of a CPUID table and the SEV-ES one,
which reads the CPUID supplied by the hypervisor.
The intent being to clarify the two back-to-back, similar CPUID
invocations.
No functional changes.
[ bp: Turn into a proper patch. ]
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/fbb24767-0e06-d1d6-36e0-1757d98aca66@amd.com
| -rw-r--r-- | arch/x86/boot/startup/sev-shared.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/arch/x86/boot/startup/sev-shared.c b/arch/x86/boot/startup/sev-shared.c index 08cc1568d8af..4e22ffd73516 100644 --- a/arch/x86/boot/startup/sev-shared.c +++ b/arch/x86/boot/startup/sev-shared.c @@ -458,6 +458,13 @@ void do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code) leaf.fn = fn; leaf.subfn = subfn; + /* + * If SNP is active, then snp_cpuid() uses the CPUID table to obtain the + * CPUID values (with possible HV interaction during post-processing of + * the values). But if SNP is not active (no CPUID table present), then + * snp_cpuid() returns -EOPNOTSUPP so that an SEV-ES guest can call the + * HV to obtain the CPUID information. + */ ret = snp_cpuid(snp_cpuid_hv_msr, NULL, &leaf); if (!ret) goto cpuid_done; @@ -465,6 +472,10 @@ void do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code) if (ret != -EOPNOTSUPP) goto fail; + /* + * This is reached by a SEV-ES guest and needs to invoke the HV for + * the CPUID data. + */ if (__sev_cpuid_hv_msr(&leaf)) goto fail; |