[xen stable-4.17] VT-d: fix iommu=no-igfx if the IOMMU scope contains fake device(s)

[patchbot@xxxxxxx]

commit 33b1c8cd86bd6c311131b8dff32bd45581e2fbc1
Author:     Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
AuthorDate: Fri Mar 31 08:29:55 2023 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Mar 31 08:29:55 2023 +0200

    VT-d: fix iommu=no-igfx if the IOMMU scope contains fake device(s)
    
    If the scope for IGD's IOMMU contains additional device that doesn't
    actually exist, iommu=no-igfx would not disable that IOMMU. In this
    particular case (Thinkpad x230) it included 00:02.1, but there is no
    such device on this platform. Consider only existing devices for the
    "gfx only" check as well as the establishing of IGD DRHD address
    (underlying is_igd_drhd(), which is used to determine applicability of
    two workarounds).
    
    Fixes: 2d7f191b392e ("VT-d: generalize and correct "iommu=no-igfx" 
handling")
    Signed-off-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
    master commit: 49de6749baa8d0addc3048defd4ef3e85cb135e9
    master date: 2023-03-23 09:16:41 +0100
---
 xen/drivers/passthrough/vtd/dmar.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/drivers/passthrough/vtd/dmar.c 
b/xen/drivers/passthrough/vtd/dmar.c
index 78d4526446..4936c20952 100644
--- a/xen/drivers/passthrough/vtd/dmar.c
+++ b/xen/drivers/passthrough/vtd/dmar.c
@@ -389,7 +389,7 @@ static int __init acpi_parse_dev_scope(
                 printk(VTDPREFIX " endpoint: %pp\n",
                        &PCI_SBDF(seg, bus, path->dev, path->fn));
 
-            if ( drhd )
+            if ( drhd && pci_device_detect(seg, bus, path->dev, path->fn) )
             {
                 if ( pci_conf_read8(PCI_SBDF(seg, bus, path->dev, path->fn),
                                     PCI_CLASS_DEVICE + 1) != 0x03
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.17