| Message ID | 10d6b416-1a20-4b1b-d39a-1bf17b2e174a@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | IOMMU: superpage support when not sharing pagetables | expand |
> From: Jan Beulich <jbeulich@suse.com> > Sent: Tuesday, January 11, 2022 12:23 AM > > I have to admit that I never understood why domain_pgd_maddr() wants to > populate all page table levels for DFN 0. I can only assume that despite > the comment there what is needed is population just down to the smallest > possible nr_pt_levels that the loop later in the function may need to > run to. Hence what is needed is the minimum of all possible > iommu->nr_pt_levels, to then be passed into addr_to_dma_page_maddr() > instead of literal 1. > > Signed-off-by: Jan Beulich <jbeulich@suse.com> Reviewed-by: Kevin Tian <kevin.tian@intel.com> > --- > v3: New. > > --- a/xen/drivers/passthrough/vtd/iommu.c > +++ b/xen/drivers/passthrough/vtd/iommu.c > @@ -55,6 +55,7 @@ bool __read_mostly iommu_snoop = true; > #endif > > static unsigned int __read_mostly nr_iommus; > +static unsigned int __read_mostly min_pt_levels = UINT_MAX; > > static struct iommu_ops vtd_ops; > static struct tasklet vtd_fault_tasklet; > @@ -482,8 +483,11 @@ static uint64_t domain_pgd_maddr(struct > { > if ( !hd->arch.vtd.pgd_maddr ) > { > - /* Ensure we have pagetables allocated down to leaf PTE. */ > - addr_to_dma_page_maddr(d, 0, 1, NULL, true); > + /* > + * Ensure we have pagetables allocated down to the smallest > + * level the loop below may need to run to. > + */ > + addr_to_dma_page_maddr(d, 0, min_pt_levels, NULL, true); > > if ( !hd->arch.vtd.pgd_maddr ) > return 0; > @@ -1381,6 +1385,8 @@ int __init iommu_alloc(struct acpi_drhd_ > return -ENODEV; > } > iommu->nr_pt_levels = agaw_to_level(agaw); > + if ( min_pt_levels > iommu->nr_pt_levels ) > + min_pt_levels = iommu->nr_pt_levels; > > if ( !ecap_coherent(iommu->ecap) ) > vtd_ops.sync_cache = sync_cache;
--- a/xen/drivers/passthrough/vtd/iommu.c +++ b/xen/drivers/passthrough/vtd/iommu.c @@ -55,6 +55,7 @@ bool __read_mostly iommu_snoop = true; #endif static unsigned int __read_mostly nr_iommus; +static unsigned int __read_mostly min_pt_levels = UINT_MAX; static struct iommu_ops vtd_ops; static struct tasklet vtd_fault_tasklet; @@ -482,8 +483,11 @@ static uint64_t domain_pgd_maddr(struct { if ( !hd->arch.vtd.pgd_maddr ) { - /* Ensure we have pagetables allocated down to leaf PTE. */ - addr_to_dma_page_maddr(d, 0, 1, NULL, true); + /* + * Ensure we have pagetables allocated down to the smallest + * level the loop below may need to run to. + */ + addr_to_dma_page_maddr(d, 0, min_pt_levels, NULL, true); if ( !hd->arch.vtd.pgd_maddr ) return 0; @@ -1381,6 +1385,8 @@ int __init iommu_alloc(struct acpi_drhd_ return -ENODEV; } iommu->nr_pt_levels = agaw_to_level(agaw); + if ( min_pt_levels > iommu->nr_pt_levels ) + min_pt_levels = iommu->nr_pt_levels; if ( !ecap_coherent(iommu->ecap) ) vtd_ops.sync_cache = sync_cache;
I have to admit that I never understood why domain_pgd_maddr() wants to populate all page table levels for DFN 0. I can only assume that despite the comment there what is needed is population just down to the smallest possible nr_pt_levels that the loop later in the function may need to run to. Hence what is needed is the minimum of all possible iommu->nr_pt_levels, to then be passed into addr_to_dma_page_maddr() instead of literal 1. Signed-off-by: Jan Beulich <jbeulich@suse.com> --- v3: New.