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

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Andrew Cooper
> Sent: 06 November 2014 15:14
> To: Paul Durrant; xen-devel@xxxxxxxxxxxxx
> 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@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.
> 

Yes, I guess.

> >   */
> > -
> > -/* EAX Features */
> 
> Spurious delete?
> 

Nope - it moved up into the above block.

> >  #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?

Yes. Typo.

  Paul

> 
> ~Andrew
> 
> >
> >  #define XEN_CPUID_MAX_NUM_LEAVES 4
> >


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