Re: CPU vendor in KVM

[Jan Kiszka <jan.kiszka@web.de>]

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On 2013-05-04 09:50, 李春奇 <Arthur Chunqi Li> wrote:
> Hi Jan and All,
> I find that when enable KVM with qemu, vendor ID of simulated CPU will be
> set the same as host, but other features such as level, family, model,
> stepping are not changed. This may bring out a confusing result, the
> simulated CPU has a vendor name of "GenuineIntel" but with family number
> "16".
> 
> I disabled the related code in function cpu_x86_find_by_name:
> diff --git a/target-i386/cpu.c b/target-i386/cpu.c
> index e2302d8..df0e82e 100644
> --- a/target-i386/cpu.c
> +++ b/target-i386/cpu.c
> @@ -1295,7 +1295,8 @@ static int cpu_x86_find_by_name(x86_def_t
> *x86_cpu_def, const char *name)
>               * KVM's sysenter/syscall emulation in compatibility mode and
>               * when doing cross vendor migration
>               */
> -            if (kvm_enabled()) {
> +            //if (kvm_enabled()) {
> +            if (0) {
>                  uint32_t  ebx = 0, ecx = 0, edx = 0;
>                  host_cpuid(0, 0, NULL, &ebx, &ecx, &edx);
>                  x86_cpu_vendor_words2str(x86_cpu_def->vendor, ebx, edx,
> ecx);
> 
> And the information of CPU remains consistent and the VM runs OK, even
> though with nested environment.
> 
> Why should qemu set simulated cpu's vendor same as the host in KVM
> environment?

The reason (and a way out) is given in the comment above the cited code.

Jan



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