Re: [Xen-devel] [PATCH] x86/HVM: support IOMMU-related Viridian CPUID bits

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: 01 August 2014 14:49
> To: xen-devel
> Cc: Andrew Cooper; Paul Durrant; Keir (Xen.org)
> Subject: [PATCH] x86/HVM: support IOMMU-related Viridian CPUID bits
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Whilst this patch is technically fine, is it of any real use? From my reading 
of the Hypervisor Top Level Functional Spec (v4.0a) these bits are only of 
relevance to the root partition.
If they do make a difference to a guest, should we not also be specifying bits 
6 and 7 in leaf 40000004:EAX and putting a value in 40000005:ECX?

  Paul

> 
> --- a/xen/arch/x86/hvm/viridian.c
> +++ b/xen/arch/x86/hvm/viridian.c
> @@ -50,6 +50,8 @@
>  #define CPUID6A_APIC_OVERLAY    (1 << 0)
>  #define CPUID6A_MSR_BITMAPS     (1 << 1)
>  #define CPUID6A_NESTED_PAGING   (1 << 3)
> +#define CPUID6A_DMA_REMAP       (1 << 4)
> +#define CPUID6A_INTR_REMAP      (1 << 5)
> 
>  int cpuid_viridian_leaves(unsigned int leaf, unsigned int *eax,
>                            unsigned int *ebx, unsigned int *ecx,
> @@ -111,6 +113,12 @@ int cpuid_viridian_leaves(unsigned int l
>              *eax |= CPUID6A_MSR_BITMAPS;
>          if ( hap_enabled(d) )
>              *eax |= CPUID6A_NESTED_PAGING;
> +        if ( iommu_enabled )
> +        {
> +            *eax |= CPUID6A_DMA_REMAP;
> +            if ( iommu_intremap )
> +                *eax |= CPUID6A_INTR_REMAP;
> +        }
>          break;
>      }
> 
> 
> 


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel