[xen stable-4.13] VT-d: don't needlessly look up DID

[patchbot@xxxxxxx]

commit a6902a65160aac72a1889a268fd5f3cebb159d8e
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Fri Apr 8 15:20:21 2022 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Apr 8 15:20:21 2022 +0200

    VT-d: don't needlessly look up DID
    
    If get_iommu_domid() in domain_context_unmap_one() fails, we better
    wouldn't clear the context entry in the first place, as we're then unable
    to issue the corresponding flush. However, we have no need to look up the
    DID in the first place: What needs flushing is very specifically the DID
    that was in the context entry before our clearing of it.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    master commit: 445ab9852d69d8957467f0036098ebec75fec092
    master date: 2022-04-07 12:29:03 +0200
---
 xen/drivers/passthrough/vtd/iommu.c | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/xen/drivers/passthrough/vtd/iommu.c 
b/xen/drivers/passthrough/vtd/iommu.c
index 6571b5dde4..4b0d6a873c 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -1821,18 +1821,12 @@ int domain_context_unmap_one(
         return 0;
     }
 
+    iommu_domid = context_domain_id(*context);
+
     context_clear_present(*context);
     context_clear_entry(*context);
     iommu_sync_cache(context, sizeof(struct context_entry));
 
-    iommu_domid = get_iommu_did(domid, iommu, !domain->is_dying);
-    if ( iommu_domid == -1 )
-    {
-        spin_unlock(&iommu->lock);
-        unmap_vtd_domain_page(context_entries);
-        return -EINVAL;
-    }
-
     rc = iommu_flush_context_device(iommu, iommu_domid,
                                     PCI_BDF2(bus, devfn),
                                     DMA_CCMD_MASK_NOBIT, 0);
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.13