Sean Christopherson <seanjc@xxxxxxxxxx> writes:
> When comparing vCPU CPUID entries against KVM's supported CPUID, mask off
> only the dynamic fields/bits instead of skipping the entire entry.
> Precisely masking bits isn't meaningfully more difficult than skipping
> entire entries, and will be necessary to maintain test coverage when a
> future commit enables OSXSAVE by default, i.e. makes one bit in all of
> CPUID.0x1 dynamic.
>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
> .../testing/selftests/kvm/x86_64/cpuid_test.c | 61 +++++++++++--------
> 1 file changed, 36 insertions(+), 25 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/x86_64/cpuid_test.c b/tools/testing/selftests/kvm/x86_64/cpuid_test.c
> index fec03b11b059..f7fdcef5fa59 100644
> --- a/tools/testing/selftests/kvm/x86_64/cpuid_test.c
> +++ b/tools/testing/selftests/kvm/x86_64/cpuid_test.c
> @@ -12,17 +12,16 @@
> #include "kvm_util.h"
> #include "processor.h"
>
> -/* CPUIDs known to differ */
> -struct {
> - u32 function;
> - u32 index;
> -} mangled_cpuids[] = {
> - /*
> - * These entries depend on the vCPU's XCR0 register and IA32_XSS MSR,
> - * which are not controlled for by this test.
> - */
> - {.function = 0xd, .index = 0},
> - {.function = 0xd, .index = 1},
> +struct cpuid_mask {
> + union {
> + struct {
> + u32 eax;
> + u32 ebx;
> + u32 ecx;
> + u32 edx;
> + };
> + u32 regs[4];
> + };
> };
>
> static void test_guest_cpuids(struct kvm_cpuid2 *guest_cpuid)
> @@ -56,17 +55,23 @@ static void guest_main(struct kvm_cpuid2 *guest_cpuid)
> GUEST_DONE();
> }
>
> -static bool is_cpuid_mangled(const struct kvm_cpuid_entry2 *entrie)
> +static struct cpuid_mask get_const_cpuid_mask(const struct kvm_cpuid_entry2 *entry)
> {
> - int i;
> + struct cpuid_mask mask;
>
> - for (i = 0; i < ARRAY_SIZE(mangled_cpuids); i++) {
> - if (mangled_cpuids[i].function == entrie->function &&
> - mangled_cpuids[i].index == entrie->index)
> - return true;
> + memset(&mask, 0xff, sizeof(mask));
> +
> + switch (entry->function) {
> + case 0xd:
> + /*
> + * CPUID.0xD.{0,1}.EBX enumerate XSAVE size based on the current
> + * XCR0 and IA32_XSS MSR values.
> + */
> + if (entry->index < 2)
> + mask.ebx = 0;
> + break;
> }
> -
> - return false;
> + return mask;
> }
>
> static void compare_cpuids(const struct kvm_cpuid2 *cpuid1,
> @@ -79,6 +84,8 @@ static void compare_cpuids(const struct kvm_cpuid2 *cpuid1,
> "CPUID nent mismatch: %d vs. %d", cpuid1->nent, cpuid2->nent);
>
> for (i = 0; i < cpuid1->nent; i++) {
> + struct cpuid_mask mask;
> +
> e1 = &cpuid1->entries[i];
> e2 = &cpuid2->entries[i];
>
> @@ -88,15 +95,19 @@ static void compare_cpuids(const struct kvm_cpuid2 *cpuid1,
> i, e1->function, e1->index, e1->flags,
> e2->function, e2->index, e2->flags);
>
> - if (is_cpuid_mangled(e1))
> - continue;
> + /* Mask off dynamic bits, e.g. OSXSAVE, when comparing entries. */
> + mask = get_const_cpuid_mask(e1);
>
> - TEST_ASSERT(e1->eax == e2->eax && e1->ebx == e2->ebx &&
> - e1->ecx == e2->ecx && e1->edx == e2->edx,
> + TEST_ASSERT((e1->eax & mask.eax) == (e2->eax & mask.eax) &&
> + (e1->ebx & mask.ebx) == (e2->ebx & mask.ebx) &&
> + (e1->ecx & mask.ecx) == (e2->ecx & mask.ecx) &&
> + (e1->edx & mask.edx) == (e2->edx & mask.edx),
> "CPUID 0x%x.%x differ: 0x%x:0x%x:0x%x:0x%x vs 0x%x:0x%x:0x%x:0x%x",
> e1->function, e1->index,
> - e1->eax, e1->ebx, e1->ecx, e1->edx,
> - e2->eax, e2->ebx, e2->ecx, e2->edx);
> + e1->eax & mask.eax, e1->ebx & mask.ebx,
> + e1->ecx & mask.ecx, e1->edx & mask.edx,
> + e2->eax & mask.eax, e2->ebx & mask.ebx,
> + e2->ecx & mask.ecx, e2->edx & mask.edx);
> }
> }
Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
--
Vitaly
