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KVM: selftests: x86: Use host's native hypercall instruction in kvm_hypercall()

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Use the host CPU's native hypercall instruction, i.e. VMCALL vs. VMMCALL,
in kvm_hypercall(), as relying on KVM to patch in the native hypercall on
a #UD for the "wrong" hypercall requires KVM_X86_QUIRK_FIX_HYPERCALL_INSN
to be enabled and flat out doesn't work if guest memory is encrypted with
a private key, e.g. for SEV VMs.

Suggested-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: David Matlack <dmatlack@google.com>
Signed-off-by: Vishal Annapurve <vannapurve@google.com>
Link: https://lore.kernel.org/r/20230111004445.416840-4-vannapurve@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Vishal Annapurve
2023-01-11 00:44:45 +00:00
committed by Sean Christopherson
parent e6df2ae3f5
commit ea25ace771
1 changed files with 8 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
tools/testing/selftests/kvm/lib/x86_64/processor.c
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@@ -1144,9 +1144,15 @@ uint64_t kvm_hypercall(uint64_t nr, uint64_t a0, uint64_t a1, uint64_t a2,
{
uint64_t r;
asm volatile("vmcall"
asm volatile("test %[use_vmmcall], %[use_vmmcall]\n\t"
"jnz 1f\n\t"
"vmcall\n\t"
"jmp 2f\n\t"
"1: vmmcall\n\t"
"2:"
: "=a"(r)
: "a"(nr), "b"(a0), "c"(a1), "d"(a2), "S"(a3));
: "a"(nr), "b"(a0), "c"(a1), "d"(a2), "S"(a3),
[use_vmmcall] "r" (host_cpu_is_amd));
return r;
}