From: Jan Beulich <jbeulich@suse.com>
Date: Fri, 8 Apr 2022 13:24:23 +0000 (+0200)
Subject: VT-d: don't needlessly look up DID
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=92e4beecd36e92d7a628738aa35a31e6781bb4cd;p=xen.git

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@suse.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
master commit: 445ab9852d69d8957467f0036098ebec75fec092
master date: 2022-04-07 12:29:03 +0200
---

diff --git a/xen/drivers/passthrough/vtd/iommu.c b/xen/drivers/passthrough/vtd/iommu.c
index 5ca1d02981..6c06baa939 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -1852,18 +1852,12 @@ 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);