[xen staging] VT-d: introduce helper to convert DID to domid_t

[patchbot@xxxxxxx]

commit d159edac73cf887fc899326edddd00133c1d206c
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Fri Dec 3 11:34:24 2021 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Dec 3 11:34:24 2021 +0100

    VT-d: introduce helper to convert DID to domid_t
    
    This is in preparation of adding another "translation" method. Take the
    combination of the extra validation both previously open-coded have been
    doing: Bounds check and bitmap check. But don't propagate the previous
    pointless check of whether ->domid_map[] was actually allocated, as
    failure there would lead to overall failure of IOMMU initialization
    anyway.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
---
 xen/drivers/passthrough/vtd/extern.h |  2 ++
 xen/drivers/passthrough/vtd/iommu.c  | 21 +++++++++++++++------
 xen/drivers/passthrough/vtd/qinval.c |  5 +----
 3 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/xen/drivers/passthrough/vtd/extern.h 
b/xen/drivers/passthrough/vtd/extern.h
index 6fb00a25c3..f97883a780 100644
--- a/xen/drivers/passthrough/vtd/extern.h
+++ b/xen/drivers/passthrough/vtd/extern.h
@@ -45,6 +45,8 @@ void disable_intremap(struct vtd_iommu *iommu);
 int iommu_alloc(struct acpi_drhd_unit *drhd);
 void iommu_free(struct acpi_drhd_unit *drhd);
 
+domid_t did_to_domain_id(const struct vtd_iommu *iommu, unsigned int did);
+
 int iommu_flush_iec_global(struct vtd_iommu *iommu);
 int iommu_flush_iec_index(struct vtd_iommu *iommu, u8 im, u16 iidx);
 void clear_fault_bits(struct vtd_iommu *iommu);
diff --git a/xen/drivers/passthrough/vtd/iommu.c 
b/xen/drivers/passthrough/vtd/iommu.c
index 2ddee7357b..b329b5d14f 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -123,15 +123,16 @@ static int context_get_domain_id(const struct 
context_entry *context,
 
     if ( iommu && context )
     {
-        unsigned int nr_dom = cap_ndoms(iommu->cap);
         unsigned int dom_index = context_domain_id(*context);
 
-        if ( dom_index < nr_dom && iommu->domid_map )
-            domid = iommu->domid_map[dom_index];
-        else
+        domid = did_to_domain_id(iommu, dom_index);
+        if ( domid == DOMID_INVALID )
+        {
             dprintk(XENLOG_DEBUG VTDPREFIX,
-                    "dom_index %u exceeds nr_dom %u or iommu has no 
domid_map\n",
-                    dom_index, nr_dom);
+                    "no domid for did %u (nr_dom %u)\n",
+                    dom_index, cap_ndoms(iommu->cap));
+            domid = -1;
+        }
     }
 
     return domid;
@@ -193,6 +194,14 @@ static void check_cleanup_domid_map(struct domain *d,
     }
 }
 
+domid_t did_to_domain_id(const struct vtd_iommu *iommu, unsigned int did)
+{
+    if ( did >= cap_ndoms(iommu->cap) || !test_bit(did, iommu->domid_bitmap) )
+        return DOMID_INVALID;
+
+    return iommu->domid_map[did];
+}
+
 static void sync_cache(const void *addr, unsigned int size)
 {
     static unsigned long clflush_size = 0;
diff --git a/xen/drivers/passthrough/vtd/qinval.c 
b/xen/drivers/passthrough/vtd/qinval.c
index b16153e298..9f291f47e5 100644
--- a/xen/drivers/passthrough/vtd/qinval.c
+++ b/xen/drivers/passthrough/vtd/qinval.c
@@ -229,10 +229,7 @@ static int __must_check dev_invalidate_sync(struct 
vtd_iommu *iommu,
     rc = queue_invalidate_wait(iommu, 0, 1, 1, 1);
     if ( rc == -ETIMEDOUT )
     {
-        struct domain *d = NULL;
-
-        if ( test_bit(did, iommu->domid_bitmap) )
-            d = rcu_lock_domain_by_id(iommu->domid_map[did]);
+        struct domain *d = rcu_lock_domain_by_id(did_to_domain_id(iommu, did));
 
         /*
          * In case the domain has been freed or the IOMMU domid bitmap is
--
generated by git-patchbot for /home/xen/git/xen.git#staging