Re: [PATCH v6 59/60] i386/cpu: Set up CPUID_HT in x86_cpu_realizefn() instead of cpu_x86_cpuid()

[Paolo Bonzini]

On 11/5/24 07:24, Xiaoyao Li wrote:
> Otherwise, it gets warnings like below when number of vcpus > 1:
>
>    warning: TDX enforces set the feature: CPUID.01H:EDX.ht [bit 28]
>
> This is because x86_confidential_guest_check_features() checks
> env->features[] instead of the cpuid date set up by cpu_x86_cpuid()
>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> ---
>   target/i386/cpu.c | 11 ++++++++++-
>   1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 472ab206d8fe..214a1b00a815 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -6571,7 +6571,6 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, 
> uint32_t count,
>           *edx = env->features[FEAT_1_EDX];
>           if (threads_per_pkg > 1) {
>               *ebx |= threads_per_pkg << 16;
> -            *edx |= CPUID_HT;
>           }
>           if (!cpu->enable_pmu) {
>               *ecx &= ~CPUID_EXT_PDCM;
> @@ -7784,6 +7783,8 @@ static void x86_cpu_realizefn(DeviceState *dev, Error 
> **errp)
>       Error *local_err = NULL;
>       unsigned requested_lbr_fmt;
>   
> +    qemu_early_init_vcpu(cs);
> +
>   #if defined(CONFIG_TCG) && !defined(CONFIG_USER_ONLY)
>       /* Use pc-relative instructions in system-mode */
>       tcg_cflags_set(cs, CF_PCREL);
> @@ -7851,6 +7852,14 @@ static void x86_cpu_realizefn(DeviceState *dev, Error 
> **errp)
>           }
>       }
>   
> +    /*
> +     * It needs to called after feature filter because KVM doesn't report HT
> +     * as supported

Does it, since kvm_arch_get_supported_cpuid() has the following line?

    if (function == 1 && reg == R_EDX) {
        ...
        /* KVM never reports CPUID_HT but QEMU can support when vcpus > 1 */
        ret |= CPUID_HT;

?

Paolo

> +     */
> +    if (cs->nr_cores * cs->nr_threads > 1) {
> +        env->features[FEAT_1_EDX] |= CPUID_HT;
> +    }