[Xen-devel] RE: [PATCH 1/6] vtd: Refactor iotlb flush code

["Kay, Allen M" <allen.m.kay@xxxxxxxxx>]

Jean,

I think this is fine.  Ack for VT-d related changes.

Allen

-----Original Message-----
From: Jean Guyader [mailto:jean.guyader@xxxxxxxxxxxxx] 
Sent: Wednesday, November 09, 2011 2:16 PM
To: Kay, Allen M
Cc: Jean Guyader; xen-devel@xxxxxxxxxxxxxxxxxxx; Tim (Xen.org)
Subject: Re: [PATCH 1/6] vtd: Refactor iotlb flush code

Allen,

The addresses in input are not necessarily aligned, to be able to use this 
feature I will have to break the range into aligned chunks of different sizes 
and flush them separatly.

I personally don't think this optimization is worth the effort.

Jean

On 09/11 02:41, Kay, Allen M wrote:
> Jean,
> 
> Page 122 of VT-d spec indicates you can invalidate multiple pages by setting 
> the Address Mask (AM) field.  Will this achieve what you wanted to do?
> 
> http://download.intel.com/technology/computing/vptech/Intel(r)_VT_for_
> Direct_IO.pdf
> 
> Allen
> 
> -----Original Message-----
> From: Jean Guyader [mailto:jean.guyader@xxxxxxxxxxxxx]
> Sent: Monday, November 07, 2011 11:42 PM
> To: Kay, Allen M
> Cc: Jean Guyader; xen-devel@xxxxxxxxxxxxxxxxxxx; Tim (Xen.org)
> Subject: Re: [PATCH 1/6] vtd: Refactor iotlb flush code
> 
> 
> Allen,
> 
> You are probably talking about __intel_iommu_iotlb_flush.
> This function takes a range of address to flush. I haven't found a function 
> in the vtd code to invalidate a range on address without doing a loop of 
> flush_iotlb_psi, so I thought that the most efficient and quick way to flush 
> a range would be to use a domain selective invalidation.
> 
> Jean
> 
> On 08/11 03:10, Kay, Allen M wrote:
> > Jean,
> > 
> > The original code does not call iommu_flush_iotlb_dsi().  What is the 
> > reason the refractored code need to use domain selective invalidation?
> > 
> > Allen
> > -----
> > 
> > +        if ( page_count > 1 || gfn == -1 )
> > +        {
> > +            if ( iommu_flush_iotlb_dsi(iommu, iommu_domid,
> > +                        0, flush_dev_iotlb) )
> > +                iommu_flush_write_buffer(iommu);
> > +        }
> > +        else
> > +        {
> > +            if ( iommu_flush_iotlb_psi(iommu, iommu_domid,
> > +                        (paddr_t)gfn << PAGE_SHIFT_4K, 0,
> > +                        !dma_old_pte_present, flush_dev_iotlb) )
> > +                iommu_flush_write_buffer(iommu);
> > 
> > -----Original Message-----
> > From: Jean Guyader [mailto:jean.guyader@xxxxxxxxxxxxx]
> > Sent: Monday, November 07, 2011 10:25 AM
> > To: xen-devel@xxxxxxxxxxxxxxxxxxx
> > Cc: tim@xxxxxxx; Kay, Allen M; Jean Guyader
> > Subject: [PATCH 1/6] vtd: Refactor iotlb flush code
> > 
> > 
> > Factorize the iotlb flush code from map_page and unmap_page into it's own 
> > function.
> > 
> > Signed-off-by: Jean Guyader <jean.guyader@xxxxxxxxxxxxx>
> > ---
> >  xen/drivers/passthrough/vtd/iommu.c |   86 
> > +++++++++++++++++-----------------
> >  1 files changed, 43 insertions(+), 43 deletions(-)
> > 

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