On 6/8/2023 9:21 PM, Peter Zijlstra wrote:
On Thu, Jun 01, 2023 at 11:16:18AM -0400, Tianyu Lan wrote:
From: Tianyu Lan <tiala@xxxxxxxxxxxxx>
In sev-snp enlightened guest, Hyper-V hypercall needs
to use vmmcall to trigger vmexit and notify hypervisor
to handle hypercall request.
There is no x86 SEV SNP feature flag support so far and
hardware provides MSR_AMD64_SEV register to check SEV-SNP
capability with MSR_AMD64_SEV_ENABLED bit. ALTERNATIVE can't
work without SEV-SNP x86 feature flag. May add later when
the associated flag is introduced.
Signed-off-by: Tianyu Lan <tiala@xxxxxxxxxxxxx>
---
arch/x86/include/asm/mshyperv.h | 44 ++++++++++++++++++++++++---------
1 file changed, 33 insertions(+), 11 deletions(-)
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 31c476f4e656..d859d7c5f5e8 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -61,16 +61,25 @@ static inline u64 hv_do_hypercall(u64 control, void *input, void *output)
u64 hv_status;
#ifdef CONFIG_X86_64
- if (!hv_hypercall_pg)
- return U64_MAX;
+ if (hv_isolation_type_en_snp()) {
+ __asm__ __volatile__("mov %4, %%r8\n"
+ "vmmcall"
+ : "=a" (hv_status), ASM_CALL_CONSTRAINT,
+ "+c" (control), "+d" (input_address)
+ : "r" (output_address)
+ : "cc", "memory", "r8", "r9", "r10", "r11");
+ } else {
+ if (!hv_hypercall_pg)
+ return U64_MAX;
- __asm__ __volatile__("mov %4, %%r8\n"
- CALL_NOSPEC
- : "=a" (hv_status), ASM_CALL_CONSTRAINT,
- "+c" (control), "+d" (input_address)
- : "r" (output_address),
- THUNK_TARGET(hv_hypercall_pg)
- : "cc", "memory", "r8", "r9", "r10", "r11");
+ __asm__ __volatile__("mov %4, %%r8\n"
+ CALL_NOSPEC
+ : "=a" (hv_status), ASM_CALL_CONSTRAINT,
+ "+c" (control), "+d" (input_address)
+ : "r" (output_address),
+ THUNK_TARGET(hv_hypercall_pg)
+ : "cc", "memory", "r8", "r9", "r10", "r11");
+ }
#else
Remains unanswered:
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Would this not generate better code with an alternative?
Hi Peter:
Thanks to review. I put the explaination in the change log.
"There is no x86 SEV SNP feature(X86_FEATURE_SEV_SNP) flag
support so far and hardware provides MSR_AMD64_SEV register
to check SEV-SNP capability with MSR_AMD64_SEV_ENABLED bit
ALTERNATIVE can't work without SEV-SNP x86 feature flag."
There is no cpuid leaf bit to check AMD SEV-SNP feature.
After some Hyper-V doesn't provides SEV and SEV-ES guest before and so
may reuse X86_FEATURE_SEV and X86_FEATURE_SEV_ES flag as alternative
feature check for Hyper-V SEV-SNP guest. Will refresh patch.