Re: [Xen-devel] [PATCH v13 0/4] add per-domain IOMMU control

[Oleksandr <olekstysh@xxxxxxxxx>]

Hi Paul


> > > I may mistake, but looks like
> > >
> > > 80ff3d338dc93260b41ffeeebb0f852c2edef9ce iommu: tidy up
> > > iommu_use_hap_pt() and need_iommu_pt_sync() macros
> > >
> > > triggers ASSERT_UNREACHABLE on Arm if no IOMMU has been found (I built
> > > with my platform's IOMMU driver disabled: # CONFIG_IPMMU_VMSA is not 
> > > set) .
> > > So, iommu_setup() calls clear_iommu_hap_pt_share() with
> > > iommu_hap_pt_share being set (CONFIG_IOMMU_FORCE_PT_SHARE=y) which,
> > > actually, triggers ASSERT.
> > Here a minimal patch, leaving 'force pt share' in place. Does this 
> > avoid the problem?
> > ---8<---
> > diff --git a/xen/common/sysctl.c b/xen/common/sysctl.c
> > index e8763c7fdf..f88a285e7f 100644
> > --- a/xen/common/sysctl.c
> > +++ b/xen/common/sysctl.c
> > @@ -268,9 +268,11 @@ long 
> > do_sysctl(XEN_GUEST_HANDLE_PARAM(xen_sysctl_t) u_sysctl)
> >           pi->max_mfn = get_upper_mfn_bound();
> >           arch_do_physinfo(pi);
> >           if ( iommu_enabled )
> > +        {
> >               pi->capabilities |= XEN_SYSCTL_PHYSCAP_directio;
> > -        if ( iommu_hap_pt_share )
> > -            pi->capabilities |= XEN_SYSCTL_PHYSCAP_iommu_hap_pt_share;
> > +            if ( iommu_hap_pt_share )
> > +                pi->capabilities |= 
> > XEN_SYSCTL_PHYSCAP_iommu_hap_pt_share;
> > +        }
> >
> >           if ( copy_to_guest(u_sysctl, op, 1) )
> >               ret = -EFAULT;
> > diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
> > index 7c3003f3f1..6a10a24128 100644
> > --- a/xen/include/xen/iommu.h
> > +++ b/xen/include/xen/iommu.h
> > @@ -68,8 +68,6 @@ static inline void clear_iommu_hap_pt_share(void)
> >   {
> >   #ifndef iommu_hap_pt_share
> >       iommu_hap_pt_share = false;
> > -#elif iommu_hap_pt_share
> > -    ASSERT_UNREACHABLE();
> >   #endif
> >   }
> > ---8<---
> >
> >    Paul
> Thank you for the patch, but I need some time to check it (now I have 
> some troubles with starting guest VM). I will inform you once I check.

With the patch applied, the issue I have faced (during Xen boot) is gone 
away. But, I haven't analyzed your "per-domain IOMMU control series" yet 
to have opinion regarding your patch itself.

I noticed the following:

When iommu_enabled = false (my case, when IOMMU driver is disable), I 
can't create guest VM if "dtdev" property is present and contains DMA 
masters in the domain config:
Parsing config from /xt/dom.cfg/domd.cfg
ERROR: passthrough not supported on this platform

Even if I add passthrough = "disabled", it still denies:

Parsing config from /xt/dom.cfg/domd.cfg
ERROR: passthrough disabled but devices are specified

Looks like, correct behavior...


--
Regards,

Oleksandr Tyshchenko


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