Re: [PATCH v2 15/18] IOMMU/x86: prefill newly allocate page tables

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

On Tue, Dec 14, 2021 at 04:10:28PM +0100, Jan Beulich wrote:
> On 14.12.2021 16:06, Roger Pau Monné wrote:
> > Forgot to comment.
> > 
> > On Fri, Sep 24, 2021 at 11:54:58AM +0200, Jan Beulich wrote:
> >> --- a/xen/drivers/passthrough/amd/pci_amd_iommu.c
> >> +++ b/xen/drivers/passthrough/amd/pci_amd_iommu.c
> >> @@ -238,7 +238,7 @@ int amd_iommu_alloc_root(struct domain *
> >>  
> >>      if ( unlikely(!hd->arch.amd.root_table) )
> >>      {
> >> -        hd->arch.amd.root_table = iommu_alloc_pgtable(d);
> >> +        hd->arch.amd.root_table = iommu_alloc_pgtable(d, 0);
> > 
> > So root tables don't get markers setup...
> > 
> > 
> >>          if ( !hd->arch.amd.root_table )
> >>              return -ENOMEM;
> >>      }
> >> --- a/xen/drivers/passthrough/vtd/iommu.c
> >> +++ b/xen/drivers/passthrough/vtd/iommu.c
> >> @@ -297,7 +297,7 @@ static uint64_t addr_to_dma_page_maddr(s
> >>              goto out;
> >>  
> >>          pte_maddr = level;
> >> -        if ( !(pg = iommu_alloc_pgtable(domain)) )
> >> +        if ( !(pg = iommu_alloc_pgtable(domain, 0)) )
> > 
> > ...likewise here.
> 
> Yes. Plus quarantine domain's page tables also don't. Neither root
> tables nor quarantine domain's are ever eligible for re-coalescing,
> so there's no point having markers there.

Quarantine won't be coalesced anyway as the same mfn is repeated over
all the entries, so it will never be a suitable candidate for
coalescing?

Thanks, Roger.