Re: [Xen-devel] [PATCH] AMD/IOMMU: restore DTE fields in amd_iommu_setup_domain_device()

[Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>]

On 13/11/2019 13:50, Jan Beulich wrote:
> Commit 1b00c16bdf ("AMD/IOMMU: pre-fill all DTEs right after table
> allocation") moved ourselves into a more secure default state, but
> didn't take sufficient care to also undo the effects when handing a
> previously disabled device back to a(nother) domain. Put the fields
> that may have been changed elsewhere back to their intended values
> (some fields amd_iommu_disable_domain_device() touches don't
> currently get written anywhere else, and hence don't need modifying
> here).
> 
> Reported-by: Sander Eikelenboom <linux@xxxxxxxxxxxxxx>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> --- a/xen/drivers/passthrough/amd/pci_amd_iommu.c
> +++ b/xen/drivers/passthrough/amd/pci_amd_iommu.c
> @@ -114,11 +114,21 @@ static void amd_iommu_setup_domain_devic
>  
>      if ( !dte->v || !dte->tv )
>      {
> +        const struct ivrs_mappings *ivrs_dev;
> +
>          /* bind DTE to domain page-tables */
>          amd_iommu_set_root_page_table(
>              dte, page_to_maddr(hd->arch.root_table), domain->domain_id,
>              hd->arch.paging_mode, valid);
>  
> +        /* Undo what amd_iommu_disable_domain_device() may have done. */
> +        ivrs_dev = &get_ivrs_mappings(iommu->seg)[req_id];
> +        if ( dte->it_root )
> +            dte->int_ctl = IOMMU_DEV_TABLE_INT_CONTROL_TRANSLATED;
> +        dte->iv = iommu_intremap;
> +        dte->ex = ivrs_dev->dte_allow_exclusion;
> +        dte->sys_mgt = MASK_EXTR(ivrs_dev->device_flags, 
> ACPI_IVHD_SYSTEM_MGMT);
> +
>          if ( pci_ats_device(iommu->seg, bus, pdev->devfn) &&
>               iommu_has_cap(iommu, PCI_CAP_IOTLB_SHIFT) )
>              dte->i = ats_enabled;
> 

Tested-by: Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>

Without this change we get stable TDRs at boot time with GPU passthrough
on AMD machines.

Igor

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