Re: [PATCH v2 3/8] x86/iommu: iommu_igfx, iommu_qinval and iommu_snoop are VT-d specific

[Xenia Ragiadakou <burzalodowa@xxxxxxxxx>]

On 1/12/23 13:49, Xenia Ragiadakou wrote:
> On 1/12/23 13:31, Jan Beulich wrote:
> > On 04.01.2023 09:44, Xenia Ragiadakou wrote:
> > > --- a/xen/drivers/passthrough/iommu.c
> > > +++ b/xen/drivers/passthrough/iommu.c
> > > @@ -82,11 +82,13 @@ static int __init cf_check 
> > > parse_iommu_param(const char *s)
> > >           else if ( ss == s + 23 && !strncmp(s, 
> > > "quarantine=scratch-page", 23) )
> > >               iommu_quarantine = IOMMU_quarantine_scratch_page;
> > >   #endif
> > > -#ifdef CONFIG_X86
> > > +#ifdef CONFIG_INTEL_IOMMU
> > >           else if ( (val = parse_boolean("igfx", s, ss)) >= 0 )
> > >               iommu_igfx = val;
> > >           else if ( (val = parse_boolean("qinval", s, ss)) >= 0 )
> > >               iommu_qinval = val;
> > > +#endif
> > You want to use no_config_param() here as well then.
> Yes. I will fix it.
>
> > > --- a/xen/include/xen/iommu.h
> > > +++ b/xen/include/xen/iommu.h
> > > @@ -74,9 +74,13 @@ extern enum __packed iommu_intremap {
> > >      iommu_intremap_restricted,
> > >      iommu_intremap_full,
> > >   } iommu_intremap;
> > > -extern bool iommu_igfx, iommu_qinval, iommu_snoop;
> > >   #else
> > >   # define iommu_intremap false
> > > +#endif
> > > +
> > > +#ifdef CONFIG_INTEL_IOMMU
> > > +extern bool iommu_igfx, iommu_qinval, iommu_snoop;
> > > +#else
> > >   # define iommu_snoop false
> > >   #endif
> > Do these declarations really need touching? In patch 2 you didn't move
> > amd_iommu_perdev_intremap's either.
> Ok, I will revert this change (as I did in v2 of patch 2) since it is 
> not needed.
Actually, my patch was altering the current behavior by defining 
iommu_snoop as false when !INTEL_IOMMU.
IIUC, there is no control over snoop behavior when using the AMD iommu. 
Hence, iommu_snoop should evaluate to true for AMD iommu.
However, when using the INTEL iommu the user can disable it via the 
"iommu" param, right?
If that's the case then iommu_snoop needs to be moved from vtd/iommu.c 
to x86/iommu.c and iommu_snoop assignment via iommu param needs to be 
guarded by CONFIG_INTEL_IOMMU.
--
Xenia