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KVM: selftests: Remove unnecessary register shuffling in fix_hypercall_test 

Use input constraints to load RAX and RBX when testing that KVM correctly
does/doesn't patch the "wrong" hypercall.  There's no need to manually
load RAX and RBX, and no reason to clobber them either (KVM is not
supposed to modify anything other than RAX).

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Message-Id: <20220928233652.783504-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2022-09-28 23:36:48 +00:00 committed by Paolo Bonzini
parent 394265079b
commit 04f2f60bef
1 changed files with 8 additions and 14 deletions
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22
tools/testing/selftests/kvm/x86_64/fix_hypercall_test.c
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@ -30,14 +30,11 @@ static uint64_t svm_do_sched_yield(uint8_t apic_id)
{
uint64_t ret;
asm volatile("mov %1, %%rax\n\t"
"mov %2, %%rbx\n\t"
"svm_hypercall_insn:\n\t"
asm volatile("svm_hypercall_insn:\n\t"
"vmmcall\n\t"
"mov %%rax, %0\n\t"
: "=r"(ret)
: "r"((uint64_t)KVM_HC_SCHED_YIELD), "r"((uint64_t)apic_id)
: "rax", "rbx", "memory");
: "=a"(ret)
: "a"((uint64_t)KVM_HC_SCHED_YIELD), "b"((uint64_t)apic_id)
: "memory");
return ret;
}
@ -47,14 +44,11 @@ static uint64_t vmx_do_sched_yield(uint8_t apic_id)
{
uint64_t ret;
asm volatile("mov %1, %%rax\n\t"
"mov %2, %%rbx\n\t"
"vmx_hypercall_insn:\n\t"
asm volatile("vmx_hypercall_insn:\n\t"
"vmcall\n\t"
"mov %%rax, %0\n\t"
: "=r"(ret)
: "r"((uint64_t)KVM_HC_SCHED_YIELD), "r"((uint64_t)apic_id)
: "rax", "rbx", "memory");
: "=a"(ret)
: "a"((uint64_t)KVM_HC_SCHED_YIELD), "b"((uint64_t)apic_id)
: "memory");
return ret;
}