Re: [PATCH 2/6] iommu: Introduce iommu_flush and iommu_flush_all.

[Wei Wang2 <wei.wang2@amd.com>]

On Tuesday 08 November 2011 11:25:15 Jean Guyader wrote:
> On 08/11 08:24, Jan Beulich wrote:
> > >>> On 07.11.11 at 18:06, Jean Guyader <jean.guyader@eu.citrix.com>
> > >>> wrote:
> > >
> > > On 07/11 04:42, Jan Beulich wrote:
> > >> >>> On 07.11.11 at 16:16, Jean Guyader <jean.guyader@eu.citrix.com>
> > >> >>> wrote:
> > >> >
> > >> > Signed-off-by: Jean Guyader <jean.guyader@eu.citrix.com>
> > >> > ---
> > >> >  xen/drivers/passthrough/iommu.c     |   20 ++++++++++++++++++++
> > >> >  xen/drivers/passthrough/vtd/iommu.c |   12 ++++++++++++
> > >> >  xen/include/xen/iommu.h             |    5 +++++
> > >> >  3 files changed, 37 insertions(+), 0 deletions(-)
> > >>
> > >> In iommu_iotlb_flush() you check whether the to-be-called function
> > >> pointer is NULL, whereas in iommu_iotlb_flush_all() you don't. I
> > >> actually think the second behavior is the correct one, but that
> > >> implies that you need to also implement respective AMD IOMMU
> > >> functions.
> > >
> > > Yes, It's an error on my part. I've updated the patch to check
> > > for the present of iotlb_flush_all before I call it now.
> >
> > But as said, I don't think this is the right solution: How can it be
> > correct on non-Intel hardware to have these functions simply do
> > nothing?
>
> These functions are only here to counter balance the dont_flush_iotlb_flag.
> If they don't acknowlage this flag doing nothing is the right thing to do.
>
> That said I can probably implement a naive version for the AMD iommu
> that will use amd_iommu_flush_pages once or in a loop.

There are some pending patches that enable ats / iotlb flush for amd iommu. 
Then, you might want to use functions: amd_iommu_flush_iotlb and 
amd_iommu_flush_all_iotlbs for this.
Thanks,
Wei

> Obviously I will remove the check for the non existing callback if I do
> that as it become mandatory.
>
> Jean
>
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