Re: [Xen-devel] [PATCH] Avoid needless flush cache when guest change MTRR

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.02.15 at 04:28, <liang.z.li@xxxxxxxxx> wrote:
> --- a/xen/arch/x86/hvm/mtrr.c
> +++ b/xen/arch/x86/hvm/mtrr.c
> @@ -791,7 +791,7 @@ HVM_REGISTER_SAVE_RESTORE(MTRR, hvm_save_mtrr_msr, 
> hvm_load_mtrr_msr,
>  
>  void memory_type_changed(struct domain *d)
>  {
> -    if ( iommu_enabled && d->vcpu && d->vcpu[0] )
> +    if ( need_iommu(d) && d->vcpu && d->vcpu[0] )
>      {
>          p2m_memory_type_changed(d);
>          flush_all(FLUSH_CACHE);

This doesn't do what title and description say: You not only suppress
the flush, but also the EPT table adjustments. Either adjust at least
the description accordingly, or make the code do what the description
says.

> --- a/xen/drivers/passthrough/pci.c
> +++ b/xen/drivers/passthrough/pci.c
> @@ -1365,6 +1365,11 @@ static int assign_device(struct domain *d, u16 seg, u8 
> bus, u8 devfn)
>              }
>          }
>          d->need_iommu = 1;
> +        /* There may be dirty cache lines when a device is assigned
> +         * and before need_iommu(d) becoming true, this will cause
> +         * memory_type_changed lose effect if memory type changes.
> +         * Call memory_type_changed here to amend this. */
> +        memory_type_changed(d);

The comment formatting does not adhere to ./CODING_STYLE.

Jan


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