> From: Jan Beulich <jbeul...@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 <jbeul...@suse.com>
Reviewed-by: Kevin Tian <kevin.t...@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;
