Re: [PATCH 2/4] target/i386: nvmm, whpx: add accel/CPU class that sets host vendor

[Xiaoyao Li <xiaoyao.li@intel.com>]

On 7/11/2025 8:06 AM, Paolo Bonzini wrote:
> NVMM and WHPX are virtualizers, and therefore they need to use
> (at least by default) the host vendor for the guest CPUID.
> Add a cpu_instance_init implementation to these accelerators.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>   target/i386/cpu.c           |  8 +++++++-
>   target/i386/nvmm/nvmm-all.c | 23 +++++++++++++++++++++++
>   target/i386/whpx/whpx-all.c | 23 +++++++++++++++++++++++
>   3 files changed, 53 insertions(+), 1 deletion(-)
> 
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 624cebc3ff7..69bdffbfe46 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -43,6 +43,7 @@
>   #include "hw/boards.h"
>   #include "hw/i386/sgx-epc.h"
>   #endif
> +#include "system/qtest.h"
>   #include "tcg/tcg-cpu.h"
>   
>   #include "disas/capstone.h"
> @@ -1943,7 +1944,7 @@ uint32_t xsave_area_size(uint64_t mask, bool compacted)
>   
>   static inline bool accel_uses_host_cpuid(void)
>   {
> -    return kvm_enabled() || hvf_enabled();
> +    return !tcg_enabled() && !qtest_enabled();
>   }
>   
>   static inline uint64_t x86_cpu_xsave_xcr0_components(X86CPU *cpu)
> diff --git a/target/i386/nvmm/nvmm-all.c b/target/i386/nvmm/nvmm-all.c
> index b4a4d50e860..69125230abb 100644
> --- a/target/i386/nvmm/nvmm-all.c
> +++ b/target/i386/nvmm/nvmm-all.c
> @@ -1207,10 +1207,33 @@ static const TypeInfo nvmm_accel_type = {
>       .class_init = nvmm_accel_class_init,
>   };
>   
> +static void nvmm_cpu_instance_init(CPUState *cs)
> +{
> +    X86CPU *cpu = X86_CPU(cs);
> +
> +    host_cpu_instance_init(cpu);

host_cpu_instance_init() only overwrites the "vendor" for "xcc->model" case.

So for "-cpu max/host" case, it will still use the one set in 
max_x86_cpu_class_init(), i.e., CPUID_VENDOR_AMD

I'm not sure if you saw my patch
https://lore.kernel.org/qemu-devel/20250701075738.3451873-2-xiaoyao.li@intel.com/

On top of it, we can simply make it

static void nvmm_cpu_instance_init(CPUState *cs)
{
     X86CPU *cpu = X86_CPU(cs);

     apply_host_vendor(cpu);
}

> +}
> +
> +static void nvmm_cpu_accel_class_init(ObjectClass *oc, const void *data)
> +{
> +    AccelCPUClass *acc = ACCEL_CPU_CLASS(oc);
> +
> +    acc->cpu_instance_init = nvmm_cpu_instance_init;
> +}
> +
> +static const TypeInfo nvmm_cpu_accel_type = {
> +    .name = ACCEL_CPU_NAME("nvmm"),
> +
> +    .parent = TYPE_ACCEL_CPU,
> +    .class_init = nvmm_cpu_accel_class_init,
> +    .abstract = true,
> +};
> +
>   static void
>   nvmm_type_init(void)
>   {
>       type_register_static(&nvmm_accel_type);
> +    type_register_static(&nvmm_cpu_accel_type);
>   }
>   
>   type_init(nvmm_type_init);
> diff --git a/target/i386/whpx/whpx-all.c b/target/i386/whpx/whpx-all.c
> index faf56e19722..b380459d6fe 100644
> --- a/target/i386/whpx/whpx-all.c
> +++ b/target/i386/whpx/whpx-all.c
> @@ -2500,6 +2500,28 @@ static void whpx_set_kernel_irqchip(Object *obj, Visitor *v,
>       }
>   }
>   
> +static void whpx_cpu_instance_init(CPUState *cs)
> +{
> +    X86CPU *cpu = X86_CPU(cs);
> +
> +    host_cpu_instance_init(cpu);
> +}
> +
> +static void whpx_cpu_accel_class_init(ObjectClass *oc, const void *data)
> +{
> +    AccelCPUClass *acc = ACCEL_CPU_CLASS(oc);
> +
> +    acc->cpu_instance_init = whpx_cpu_instance_init;
> +}
> +
> +static const TypeInfo whpx_cpu_accel_type = {
> +    .name = ACCEL_CPU_NAME("whpx"),
> +
> +    .parent = TYPE_ACCEL_CPU,
> +    .class_init = whpx_cpu_accel_class_init,
> +    .abstract = true,
> +};
> +
>   /*
>    * Partition support
>    */
> @@ -2726,6 +2748,7 @@ static const TypeInfo whpx_accel_type = {
>   static void whpx_type_init(void)
>   {
>       type_register_static(&whpx_accel_type);
> +    type_register_static(&whpx_cpu_accel_type);
>   }
>   
>   bool init_whp_dispatch(void)