Re: [PATCH v2 5/6] x86/iommu: switch hwdom IOMMU to use a rangeset

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, Dec 05, 2023 at 04:27:05PM +0100, Jan Beulich wrote:
> On 04.12.2023 10:43, Roger Pau Monne wrote:
> > @@ -476,58 +406,55 @@ void __hwdom_init arch_iommu_hwdom_init(struct domain 
> > *d)
> >      if ( !map )
> >          panic("IOMMU init: unable to allocate rangeset\n");
> >  
> > -    max_pfn = (GB(4) >> PAGE_SHIFT) - 1;
> > -    top = max(max_pdx, pfn_to_pdx(max_pfn) + 1);
> > +    if ( iommu_hwdom_inclusive )
> > +    {
> > +        /* Add the whole range below 4GB, UNUSABLE regions will be 
> > removed. */
> > +        rc = rangeset_add_range(map, 0, max_pfn);
> > +        if ( rc )
> > +            panic("IOMMU inclusive mappings can't be added: %d\n",
> > +                  rc);
> > +    }
> >  
> > -    for ( i = 0, start = 0, count = 0; i < top; )
> > +    for ( i = 0; i < e820.nr_map; i++ )
> >      {
> > -        unsigned long pfn = pdx_to_pfn(i);
> > -        unsigned int perms = hwdom_iommu_map(d, pfn, max_pfn);
> > +        struct e820entry entry = e820.map[i];
> >  
> > -        if ( !perms )
> > -            /* nothing */;
> > -        else if ( paging_mode_translate(d) )
> > +        switch ( entry.type )
> >          {
> > -            int rc;
> > +        case E820_UNUSABLE:
> > +            if ( !iommu_hwdom_inclusive || PFN_DOWN(entry.addr) > max_pfn )
> > +                continue;
> 
> The !iommu_hwdom_inclusive part isn't really needed here, is it? The ...

Nor the PFN_DOWN(entry.addr) > max_pfn.

> > -            rc = p2m_add_identity_entry(d, pfn,
> > -                                        perms & IOMMUF_writable ? 
> > p2m_access_rw
> > -                                                                : 
> > p2m_access_r,
> > -                                        0);
> > +            rc = rangeset_remove_range(map, PFN_DOWN(entry.addr),
> > +                                       PFN_DOWN(entry.addr + entry.size - 
> > 1));
> 
> ... call here would then simply be a no-op, as it looks. And things would
> overall look more safe if the removal was skipped for fewer reasons.

OK, the removal can be done unconditionally if so desired.

> > @@ -605,7 +532,7 @@ void __hwdom_init arch_iommu_hwdom_init(struct domain 
> > *d)
> >      rangeset_destroy(map);
> >  
> >      /* Use if to avoid compiler warning */
> > -    if ( iommu_iotlb_flush_all(d, flush_flags) )
> > +    if ( iommu_iotlb_flush_all(d, map_data.flush_flags) )
> >          return;
> >  }
> 
> Ah yes, here is said change. But I think for correctness this wants
> moving to the earlier patch.

OK, so something like:

map_data.flush_flags |= flush_flags;

And adjusting the iommu_iotlb_flush_all() would be fine in this patch
context.

Thanks, Roger.