Re: [PATCH RESEND 2/5] KVM: x86: selftests: Alter the instruction of hypercall on Hygon

[Sean Christopherson <seanjc@google.com>]

On Mon, Feb 09, 2026, Zhiquan Li wrote:
> Hygon architecture uses VMMCALL as guest hypercall instruction.  Now,
> the test like "fix hypercall" uses VMCALL and then results in test
> failure.
> 
> Utilize the Hygon-specific flag to identify if the test is running on
> Hygon CPU and alter the instruction of hypercall if needed.
> 
> Signed-off-by: Zhiquan Li <zhiquan_li@163.com>
> ---
>  tools/testing/selftests/kvm/lib/x86/processor.c      | 3 ++-
>  tools/testing/selftests/kvm/x86/fix_hypercall_test.c | 2 +-
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/lib/x86/processor.c b/tools/testing/selftests/kvm/lib/x86/processor.c
> index bbd3336f22eb..64f9ecd2387d 100644
> --- a/tools/testing/selftests/kvm/lib/x86/processor.c
> +++ b/tools/testing/selftests/kvm/lib/x86/processor.c
> @@ -1229,7 +1229,8 @@ const struct kvm_cpuid_entry2 *get_cpuid_entry(const struct kvm_cpuid2 *cpuid,
>  		     "1: vmmcall\n\t"					\
>  		     "2:"						\
>  		     : "=a"(r)						\
> -		     : [use_vmmcall] "r" (host_cpu_is_amd), inputs);	\
> +		     : [use_vmmcall] "r"				\
> +		     (host_cpu_is_amd || host_cpu_is_hygon), inputs);	\

Rather than play a constant game of whack-a-mole and end up with a huge number of
"host_cpu_is_amd || host_cpu_is_hygon" checks, I would prefer to add (in addition
to host_cpu_is_hygon) a "host_cpu_is_amd_compatible" flag.

E.g. slotted in after patch 1, something like this:

---
 tools/testing/selftests/kvm/include/x86/processor.h  | 1 +
 tools/testing/selftests/kvm/lib/x86/processor.c      | 8 ++++++--
 tools/testing/selftests/kvm/x86/fix_hypercall_test.c | 2 +-
 tools/testing/selftests/kvm/x86/msrs_test.c          | 2 +-
 tools/testing/selftests/kvm/x86/xapic_state_test.c   | 2 +-
 5 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/x86/processor.h b/tools/testing/selftests/kvm/include/x86/processor.h
index 1338de7111e7..40e3deb64812 100644
--- a/tools/testing/selftests/kvm/include/x86/processor.h
+++ b/tools/testing/selftests/kvm/include/x86/processor.h
@@ -22,6 +22,7 @@
 extern bool host_cpu_is_intel;
 extern bool host_cpu_is_amd;
 extern bool host_cpu_is_hygon;
+extern bool host_cpu_is_amd_compatible;
 extern uint64_t guest_tsc_khz;
 
 #ifndef MAX_NR_CPUID_ENTRIES
diff --git a/tools/testing/selftests/kvm/lib/x86/processor.c b/tools/testing/selftests/kvm/lib/x86/processor.c
index f6b1c5324931..7b7fd2ad148f 100644
--- a/tools/testing/selftests/kvm/lib/x86/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86/processor.c
@@ -24,6 +24,7 @@ vm_vaddr_t exception_handlers;
 bool host_cpu_is_amd;
 bool host_cpu_is_intel;
 bool host_cpu_is_hygon;
+bool host_cpu_is_amd_compatible;
 bool is_forced_emulation_enabled;
 uint64_t guest_tsc_khz;
 
@@ -794,6 +795,7 @@ void kvm_arch_vm_post_create(struct kvm_vm *vm, unsigned int nr_vcpus)
 	sync_global_to_guest(vm, host_cpu_is_intel);
 	sync_global_to_guest(vm, host_cpu_is_amd);
 	sync_global_to_guest(vm, host_cpu_is_hygon);
+	sync_global_to_guest(vm, host_cpu_is_amd_compatible);
 	sync_global_to_guest(vm, is_forced_emulation_enabled);
 	sync_global_to_guest(vm, pmu_errata_mask);
 
@@ -1350,7 +1352,8 @@ const struct kvm_cpuid_entry2 *get_cpuid_entry(const struct kvm_cpuid2 *cpuid,
 		     "1: vmmcall\n\t"					\
 		     "2:"						\
 		     : "=a"(r)						\
-		     : [use_vmmcall] "r" (host_cpu_is_amd), inputs);	\
+		     : [use_vmmcall] "r" (host_cpu_is_amd_compatible),	\
+		       inputs);						\
 									\
 	r;								\
 })
@@ -1391,7 +1394,7 @@ unsigned long vm_compute_max_gfn(struct kvm_vm *vm)
 	max_gfn = (1ULL << (guest_maxphyaddr - vm->page_shift)) - 1;
 
 	/* Avoid reserved HyperTransport region on AMD processors.  */
-	if (!host_cpu_is_amd)
+	if (!host_cpu_is_amd_compatible)
 		return max_gfn;
 
 	/* On parts with <40 physical address bits, the area is fully hidden */
@@ -1427,6 +1430,7 @@ void kvm_selftest_arch_init(void)
 	host_cpu_is_intel = this_cpu_is_intel();
 	host_cpu_is_amd = this_cpu_is_amd();
 	host_cpu_is_hygon = this_cpu_is_hygon();
+	host_cpu_is_amd_compatible = host_cpu_is_amd || host_cpu_is_hygon;
 	is_forced_emulation_enabled = kvm_is_forced_emulation_enabled();
 
 	kvm_init_pmu_errata();
diff --git a/tools/testing/selftests/kvm/x86/fix_hypercall_test.c b/tools/testing/selftests/kvm/x86/fix_hypercall_test.c
index 762628f7d4ba..00b6e85735dd 100644
--- a/tools/testing/selftests/kvm/x86/fix_hypercall_test.c
+++ b/tools/testing/selftests/kvm/x86/fix_hypercall_test.c
@@ -52,7 +52,7 @@ static void guest_main(void)
 	if (host_cpu_is_intel) {
 		native_hypercall_insn = vmx_vmcall;
 		other_hypercall_insn  = svm_vmmcall;
-	} else if (host_cpu_is_amd) {
+	} else if (host_cpu_is_amd_compatible) {
 		native_hypercall_insn = svm_vmmcall;
 		other_hypercall_insn  = vmx_vmcall;
 	} else {
diff --git a/tools/testing/selftests/kvm/x86/msrs_test.c b/tools/testing/selftests/kvm/x86/msrs_test.c
index 40d918aedce6..4c97444fdefe 100644
--- a/tools/testing/selftests/kvm/x86/msrs_test.c
+++ b/tools/testing/selftests/kvm/x86/msrs_test.c
@@ -81,7 +81,7 @@ static u64 fixup_rdmsr_val(u32 msr, u64 want)
 	 * is supposed to emulate that behavior based on guest vendor model
 	 * (which is the same as the host vendor model for this test).
 	 */
-	if (!host_cpu_is_amd)
+	if (!host_cpu_is_amd_compatible)
 		return want;
 
 	switch (msr) {
diff --git a/tools/testing/selftests/kvm/x86/xapic_state_test.c b/tools/testing/selftests/kvm/x86/xapic_state_test.c
index 3b4814c55722..0c5e12f5f14e 100644
--- a/tools/testing/selftests/kvm/x86/xapic_state_test.c
+++ b/tools/testing/selftests/kvm/x86/xapic_state_test.c
@@ -248,7 +248,7 @@ int main(int argc, char *argv[])
 	 * drops writes, AMD does not).  Account for the errata when checking
 	 * that KVM reads back what was written.
 	 */
-	x.has_xavic_errata = host_cpu_is_amd &&
+	x.has_xavic_errata = host_cpu_is_amd_compatible &&
 			     get_kvm_amd_param_bool("avic");
 
 	vcpu_clear_cpuid_feature(x.vcpu, X86_FEATURE_X2APIC);

base-commit: 391774310e7309b5a1ee12fac9264e95b1d4a6ee
--