Re: [Xen-devel] Xen-unstable: AMD-Vi: update_paging_mode Try to access pdev_list without aquiring pcidevs_lock.

[Jan Beulich <jbeulich@xxxxxxxx>]

On 11.11.2019 22:38, Sander Eikelenboom wrote:
> When supplying "pci=nomsi" to the guest kernel, the device works fine,
> and I don't get the "INVALID_DEV_REQUEST".
> 
> After reverting 1b00c16bdf, the device works fine 
> and I don't get the INVALID_DEV_REQUEST, 

Could you give the patch below a try? That commit took care of only
securing ourselves, but not of relaxing things again when a device
gets handed to a guest for actual use.

Jan

AMD/IOMMU: restore DTE fields in amd_iommu_setup_domain_device()

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>

--- unstable.orig/xen/drivers/passthrough/amd/pci_amd_iommu.c
+++ unstable/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;


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