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

Paolo Bonzini
2024-11-05T09:12:26Z

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;
> + }