[xen staging-4.13] VT-d: adjust domid map updating when unmapping context

[patchbot@xxxxxxx]

commit ddb3edbc9f063a2b798393ca52c236686a11cce6
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Jul 15 09:42:18 2021 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Jul 15 09:42:18 2021 +0200

    VT-d: adjust domid map updating when unmapping context
    
    When an earlier error occurred, cleaning up the domid mapping data is
    wrong, as references likely still exist. The only exception to this is
    when the actual unmapping worked, but some flush failed (supposedly
    impossible after XSA-373). The guest will get crashed in such a case
    though, so add fallback cleanup to domain destruction to cover this
    case. This in turn makes it desirable to silence the dprintk() in
    domain_iommu_domid().
    
    Note that no error will be returned anymore when the lookup fails - in
    the common case lookup failure would already have caused
    domain_context_unmap_one() to fail, yet even from a more general
    perspective it doesn't look right to fail domain_context_unmap() in such
    a case when this was the last device, but not when any earlier unmap was
    otherwise successful.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
    master commit: 32655880057ce2829f962d46916ea6cec60f98d3
    master date: 2021-06-24 16:29:13 +0200
---
 xen/drivers/passthrough/vtd/iommu.c | 39 +++++++++++++++++++++++--------------
 1 file changed, 24 insertions(+), 15 deletions(-)

diff --git a/xen/drivers/passthrough/vtd/iommu.c 
b/xen/drivers/passthrough/vtd/iommu.c
index 77aaef596a..0ee18bdcc3 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -73,9 +73,11 @@ static int domain_iommu_domid(struct domain *d,
         i = find_next_bit(iommu->domid_bitmap, nr_dom, i+1);
     }
 
-    dprintk(XENLOG_ERR VTDPREFIX,
-            "Cannot get valid iommu domid: domid=%d iommu->index=%d\n",
-            d->domain_id, iommu->index);
+    if ( !d->is_dying )
+        dprintk(XENLOG_ERR VTDPREFIX,
+                "Cannot get valid iommu %u domid: %pd\n",
+                iommu->index, d);
+
     return -1;
 }
 
@@ -140,6 +142,17 @@ static int context_get_domain_id(struct context_entry 
*context,
     return domid;
 }
 
+static void cleanup_domid_map(struct domain *domain, struct vtd_iommu *iommu)
+{
+    int iommu_domid = domain_iommu_domid(domain, iommu);
+
+    if ( iommu_domid >= 0 )
+    {
+        clear_bit(iommu_domid, iommu->domid_bitmap);
+        iommu->domid_map[iommu_domid] = 0;
+    }
+}
+
 static int iommus_incoherent;
 
 static void sync_cache(const void *addr, unsigned int size)
@@ -1752,6 +1765,9 @@ static int domain_context_unmap(struct domain *domain, u8 
devfn,
         goto out;
     }
 
+    if ( ret )
+        goto out;
+
     /*
      * if no other devices under the same iommu owned by this domain,
      * clear iommu in iommu_bitmap and clear domain_id in domid_bitmp
@@ -1771,19 +1787,8 @@ static int domain_context_unmap(struct domain *domain, 
u8 devfn,
 
     if ( found == 0 )
     {
-        int iommu_domid;
-
         clear_bit(iommu->index, &dom_iommu(domain)->arch.iommu_bitmap);
-
-        iommu_domid = domain_iommu_domid(domain, iommu);
-        if ( iommu_domid == -1 )
-        {
-            ret = -EINVAL;
-            goto out;
-        }
-
-        clear_bit(iommu_domid, iommu->domid_bitmap);
-        iommu->domid_map[iommu_domid] = 0;
+        cleanup_domid_map(domain, iommu);
     }
 
 out:
@@ -1794,6 +1799,7 @@ static void iommu_domain_teardown(struct domain *d)
 {
     struct domain_iommu *hd = dom_iommu(d);
     struct mapped_rmrr *mrmrr, *tmp;
+    const struct acpi_drhd_unit *drhd;
 
     if ( list_empty(&acpi_drhd_units) )
         return;
@@ -1813,6 +1819,9 @@ static void iommu_domain_teardown(struct domain *d)
     iommu_free_pagetable(hd->arch.pgd_maddr, agaw_to_level(hd->arch.agaw));
     hd->arch.pgd_maddr = 0;
     spin_unlock(&hd->arch.mapping_lock);
+
+    for_each_drhd_unit ( drhd )
+        cleanup_domid_map(d, drhd->iommu);
 }
 
 static int __must_check intel_iommu_map_page(struct domain *d, dfn_t dfn,
--
generated by git-patchbot for /home/xen/git/xen.git#staging-4.13