Re: [PATCH] target/i386: Fix cpuid level for AMD

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* zhenwei pi (pizhenwei@bytedance.com) wrote:
> A AMD server typically has cpuid level 0x10(test on Rome/Milan), it
> should not be changed to 0x1f in multi-dies case.
> 
> Fixes: a94e1428991 (target/i386: Add CPUID.1F generation support
> for multi-dies PCMachine)
> Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>

(Copying in Babu)

Hmm I think you're right.  I've cc'd in Babu and Wei.

Eduardo: What do we need to do about compatibility, do we need to wire
this to machine type or CPU version?

Dave

> ---
>  target/i386/cpu.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index a9fe1662d3..3934c559e4 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -5961,8 +5961,12 @@ void x86_cpu_expand_features(X86CPU *cpu, Error **errp)
>              }
>          }
>  
> -        /* CPU topology with multi-dies support requires CPUID[0x1F] */
> -        if (env->nr_dies > 1) {
> +        /*
> +         * Intel CPU topology with multi-dies support requires CPUID[0x1F].
> +         * For AMD Rome/Milan, cpuid level is 0x10, and guest OS should detect
> +         * extended toplogy by leaf 0xB. Only adjust it for Intel CPU.
> +         */
> +        if ((env->nr_dies > 1) && IS_INTEL_CPU(env)) {
>              x86_cpu_adjust_level(cpu, &env->cpuid_min_level, 0x1F);
>          }
>  
> -- 
> 2.25.1
> 
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK