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

[Jean Guyader <jean.guyader@xxxxxxxxxxxxx>]

On 08/11 10:39, Wei Wang2 wrote:
> 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@xxxxxxxxxxxxx>
> > > >>> wrote:
> > > >
> > > > On 07/11 04:42, Jan Beulich wrote:
> > > >> >>> On 07.11.11 at 16:16, Jean Guyader <jean.guyader@xxxxxxxxxxxxx>
> > > >> >>> wrote:
> > > >> >
> > > >> > Signed-off-by: Jean Guyader <jean.guyader@xxxxxxxxxxxxx>
> > > >> > ---
> > > >> >  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
> 

Ok, I'll do that in the next version.

Thanks,
Jean

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