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

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 06/11/14 15:16, Paul Durrant wrote:
>> -----Original Message-----
>> From: Andrew Cooper
>> Sent: 06 November 2014 15:14
>> To: Paul Durrant; xen-devel@lists.xen.org
>> Cc: Keir (Xen.org); Jan Beulich
>> Subject: Re: [Xen-devel] [PATCH] x86/hvm: Extend HVM cpuid leaf with vcpu
>> id
>>
>> 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@citrix.com>
>>> Cc: Keir Fraser <keir@xen.org>
>>> Cc: Jan Beulich <jbeulich@suse.com>
>>> ---
>>>  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.
>>
> Yes, I guess.
>
>>>   */
>>> -
>>> -/* EAX Features */
>> Spurious delete?
>>
> Nope - it moved up into the above block.

Ah - I see now.  That looks ok.

With the other changes, Reviewed-by: Andrew Cooper
<andrew.cooper3@citrix.com>

~Andrew