[V3 PATCH 4/4] KVM: selftests: x86: Precompute the cpu type

Vishal Annapurve
2022-10-13T12:14:07Z

Cache the vendor CPU type in a global variable so that multiple calls
to is_amd/intel_cpu() do not need to re-execute CPUID.

Sync the global variable is_cpu_amd into the guest so the guest can also
avoid executing CPUID instruction.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Vishal Annapurve <vannapurve@google.com>
---
tools/testing/selftests/kvm/lib/x86_64/processor.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
index fa65e8142c16..f508e58346e9 100644
--- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
@@ -19,6 +19,7 @@
#define MAX_NR_CPUID_ENTRIES 100

vm_vaddr_t exception_handlers;
+static bool is_cpu_amd;

static void regs_dump(FILE *stream, struct kvm_regs *regs, uint8_t indent)
{
@@ -1046,7 +1047,7 @@ static bool cpu_vendor_string_is(const char *vendor)

bool is_intel_cpu(void)
{
- return cpu_vendor_string_is("GenuineIntel");
+ return !is_cpu_amd;
}

/*
@@ -1054,7 +1055,7 @@ bool is_intel_cpu(void)
*/
bool is_amd_cpu(void)
{
- return cpu_vendor_string_is("AuthenticAMD");
+ return is_cpu_amd;
}

void kvm_get_cpu_address_width(unsigned int *pa_bits, unsigned int *va_bits)
@@ -1328,8 +1329,13 @@ bool vm_is_unrestricted_guest(struct kvm_vm *vm)
return get_kvm_intel_param_bool("unrestricted_guest");
}

+void kvm_selftest_arch_init(void)
+{
+ is_cpu_amd = cpu_vendor_string_is("AuthenticAMD");
+}

void kvm_arch_vm_post_create(struct kvm_vm *vm)
{
vm_create_irqchip(vm);
+ sync_global_to_guest(vm, is_cpu_amd);
}
--
2.38.0.rc1.362.ged0d419d3c-goog