Re: [Xen-devel] [PATCH v4 08/28] x86/vvtd: Add MMIO handler for VVTD

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Feb 23, 2018 at 05:07:09PM +0000, Roger Pau Monné wrote:
> On Thu, Feb 22, 2018 at 02:20:12PM +0800, Chao Gao wrote:
> > On Fri, Feb 09, 2018 at 05:51:29PM +0000, Roger Pau Monné wrote:
> > >On Sat, Feb 10, 2018 at 01:21:09AM +0800, Chao Gao wrote:
> > >> On Fri, Feb 09, 2018 at 04:39:15PM +0000, Roger Pau Monné wrote:
> > >> >On Fri, Nov 17, 2017 at 02:22:15PM +0800, Chao Gao wrote:
> > >> >> This patch adds VVTD MMIO handler to deal with MMIO access.
> > >> >> 
> > >> >> Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
> > >> >> Signed-off-by: Lan Tianyu <tianyu.lan@xxxxxxxxx>
> > >> >> ---
> > >> >> v4:
> > >> >>  - only trap the register emulated in vvtd_in_range().
> > >> >>    i.e. replace PAGE_SIZE with the VVTD_MAX_OFFSET
> > >> >> ---
> > >> >>  xen/drivers/passthrough/vtd/vvtd.c | 55 
> > >> >> ++++++++++++++++++++++++++++++++++++++
> > >> >>  1 file changed, 55 insertions(+)
> > >> >> 
> > >> >> diff --git a/xen/drivers/passthrough/vtd/vvtd.c 
> > >> >> b/xen/drivers/passthrough/vtd/vvtd.c
> > >> >> index 9f76ccf..d78d878 100644
> > >> >> --- a/xen/drivers/passthrough/vtd/vvtd.c
> > >> >> +++ b/xen/drivers/passthrough/vtd/vvtd.c
> > >> >
> > >> >Now that I look at this, this is the wrong folder. This should be in
> > >> >xen/arch/x86/hvm with the rest of the emulated devices.
> > >> 
> > >> It is a problem we discussed in previous versions. AMD puts its vIOMMU
> > >> (iommu_guest.c) in xen/drivers/passthrough/amd/. We are following what
> > >> they did. I don't have special taste on this. If no one objects to your
> > >> suggestion, I will move it to xen/arch/x86/hvm/. Maybe create a new
> > >> intel directory since it's intel-specific and won't be used by AMD.
> > >
> > >Oh, it's been quite some time since I've reviewed that, so TBH I
> > >didn't remember that discussion.
> > >
> > >If the AMD viommu thing is already there I guess it doesn't hurt...
> > >Also, have you checked whether it can be converted to use the
> > >infrastructure that you add here?
> > 
> > Not yet. It seems that we have no method to use AMD vIOMMU now.
> > And I notice that Wei plans to remove AMD vIOMMU.
> > 
> > I can convert AMD vIOMMU implementation to use this infrastructure if we
> > finally decide to preserve AMD vIOMMU.
> 
> Oh, OK, I had no idea we where planning to remove the AMD vIOMMU
> stuff.

That code was never properly hooked up in the first place. It has been
dead code since 2012-ish so I assumed noone cared.

I don't know if AMD maintainer will object to the removal though.

Wei.

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