Re: [Qemu-devel] [FIX] X86 CPU topology broken in KVM mode

[Anthony Liguori]

On 09/06/2011 11:21 PM, Bharata B Rao wrote:
> Hi,
>
> Sometime back I posted a patch for fixing x86 CPU topology (
> http://lists.gnu.org/archive/html/qemu-devel/2011-08/msg02022.html).
> Here is the next version of the fix which addresses all but one
> comment received during that post.
>
> - Fixed code style issues
> - Ensured that the fix doesn't break TCG mode
> - I am not sure what is the problem with i486 as I haven't been able
> to boot an i486 VM successfully, hence haven't attempted to fix this.
>
> I have tested following scenarios and found the fix to be working fine.
>
> KVM: (with --enable-kvm)
> -smp sockets=1,cores=4,threads=2
> -smp sockets=4,cores=4,threads=2
> -cpu core2duo sockets=1,cores=4,threads=2
> -cpu core2duo sockets=2,cores=4,threads=2
>
> TCG: (without --enable-kvm)
> -cpu core2duo sockets=1,cores=4,threads=2
> -cpu core2duo sockets=2,cores=4,threads=2
>
> Here is the updated patch which now applies against qemu.git.
>
> ********************
> Fix apic id enumeration
>
> apic id returned to guest kernel in ebx for cpuid(function=1) depends on
> CPUX86State->cpuid_apic_id which gets populated after the cpuid information
> is cached in the host kernel.
>
> Fix this by setting cpuid_apic_id before cpuid information is passed to
> the host kernel. This is done by moving the setting of cpuid_apic_id
> to cpu_x86_init() where it will work for both KVM as well as TCG modes.
>
> Signed-off-by: Bharata B Rao<address@hidden>

Please post patches as top-level threads with [PATCH] in the subject. 
Please use git diff or better yet, git-send-email.

Regards,

Anthony Liguori

> ---
>   hw/pc.c              |    1 -
>   target-i386/helper.c |    5 +++++
>   2 files changed, 5 insertions(+), 1 deletion(-)
>
> Index: qemu/hw/pc.c
> ===================================================================
> --- qemu.orig/hw/pc.c
> +++ qemu/hw/pc.c
> @@ -933,7 +933,6 @@ static CPUState *pc_new_cpu(const char *
>           exit(1);
>       }
>       if ((env->cpuid_features&  CPUID_APIC) || smp_cpus>  1) {
> -        env->cpuid_apic_id = env->cpu_index;
>           env->apic_state = apic_init(env, env->cpuid_apic_id);
>       }
>       qemu_register_reset(pc_cpu_reset, env);
> Index: qemu/target-i386/helper.c
> ===================================================================
> --- qemu.orig/target-i386/helper.c
> +++ qemu/target-i386/helper.c
> @@ -1256,6 +1256,11 @@ CPUX86State *cpu_x86_init(const char *cp
>           cpu_x86_close(env);
>           return NULL;
>       }
> +
> +    if (env->cpuid_features&  CPUID_APIC) {
> +        env->cpuid_apic_id = env->cpu_index;
> +    }
> +
>       mce_init(env);
>
>       qemu_init_vcpu(env);
> *************************
>
> Regards,
> Bharata.
> --
>   http://bharata.sulekha.com/blog/posts.htm, http://raobharata.wordpress.com/