Re: [Xen-devel] [PATCH] x86/hvm: Extend HVM cpuid leaf with vcpu id

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 06/11/14 15:07, Paul Durrant wrote:
> To perform certain hypercalls HVM guests need to use Xen's idea of
> vcpu id, which may well not match the guest OS idea of CPU id.
> This patch adds vcpu id to the HVM cpuid leaf allowing the guest
> to build a mapping.
>
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> Cc: Keir Fraser <keir@xxxxxxx>
> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> ---
>  xen/arch/x86/hvm/hvm.c              |    4 ++++
>  xen/include/public/arch-x86/cpuid.h |    5 +++--
>  2 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> index 78f519d..d9a5706 100644
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -4189,6 +4189,10 @@ void hvm_hypervisor_cpuid_leaf(uint32_t sub_idx,
>           * foreign pages) has valid IOMMU entries.
>           */
>          *eax |= XEN_HVM_CPUID_IOMMU_MAPPINGS;
> +
> +        /* Indicate presence of vcpu id and set it in ebx */
> +        *eax |= XEN_HVM_CPUID_VCPU_ID_PRESENT;
> +        *ebx = current->vcpu_id;
>      }
>  }
>  
> diff --git a/xen/include/public/arch-x86/cpuid.h 
> b/xen/include/public/arch-x86/cpuid.h
> index 6005dfe..8ccb6e1 100644
> --- a/xen/include/public/arch-x86/cpuid.h
> +++ b/xen/include/public/arch-x86/cpuid.h
> @@ -76,13 +76,14 @@
>  /*
>   * Leaf 5 (0x40000x04)
>   * HVM-specific features
> + * EAX: Features
> + * EBX: VCPU ID

Probably want "iff EAX & VCPU_ID_PRESENT" in this comment.

>   */
> -
> -/* EAX Features */

Spurious delete?

>  #define XEN_HVM_CPUID_APIC_ACCESS_VIRT (1u << 0) /* Virtualized APIC 
> registers */
>  #define XEN_HVM_CPUID_X2APIC_VIRT      (1u << 1) /* Virtualized x2APIC 
> accesses */
>  /* Memory mapped from other domains has valid IOMMU entries */
>  #define XEN_HVM_CPUID_IOMMU_MAPPINGS   (1u << 2)
> +#define XEN_HVM_CPUID_VCPU_ID_PRESENT  (1u << 3) /* vcpu is present in EBX */

vcpu id?

~Andrew

>  
>  #define XEN_CPUID_MAX_NUM_LEAVES 4
>  


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