[Xen-changelog] [xen stable-4.8] VT-d: correct dma_msi_set_affinity()

[patchbot@xxxxxxx]

commit 080a31b6f95e17e3624b8f716653a6e9009912d6
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Wed Jan 18 09:48:57 2017 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Jan 18 09:48:57 2017 +0100

    VT-d: correct dma_msi_set_affinity()
    
    Commit 83cd2038fe ("VT-d: use msi_compose_msg()) together with
    15aa6c6748 ("amd iommu: use base platform MSI implementation"),
    introducing the use of a per-CPU scratch CPU mask, went too far:
    dma_msi_set_affinity() may, at least in theory, be called in
    interrupt context, and hence the use of that scratch variable is not
    correct.
    
    Since the function overwrites the destination information anyway,
    allow msi_compose_msg() to be called with a NULL CPU mask, avoiding
    the use of that scratch variable.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: 7f885a1f49a75c770360b030666a5c1545156e5c
    master date: 2016-12-16 14:33:43 +0100
---
 xen/arch/x86/msi.c                  | 48 ++++++++++++++++++-------------------
 xen/drivers/passthrough/vtd/iommu.c |  6 ++---
 2 files changed, 26 insertions(+), 28 deletions(-)

diff --git a/xen/arch/x86/msi.c b/xen/arch/x86/msi.c
index 649607a..2c38adb 100644
--- a/xen/arch/x86/msi.c
+++ b/xen/arch/x86/msi.c
@@ -160,39 +160,37 @@ static bool_t msix_memory_decoded(const struct pci_dev 
*dev, unsigned int pos)
  */
 void msi_compose_msg(unsigned vector, const cpumask_t *cpu_mask, struct 
msi_msg *msg)
 {
-    unsigned dest;
-
     memset(msg, 0, sizeof(*msg));
-    if ( !cpumask_intersects(cpu_mask, &cpu_online_map) )
+
+    if ( vector < FIRST_DYNAMIC_VECTOR )
         return;
 
-    if ( vector )
+    if ( cpu_mask )
     {
         cpumask_t *mask = this_cpu(scratch_mask);
 
+        if ( !cpumask_intersects(cpu_mask, &cpu_online_map) )
+            return;
+
         cpumask_and(mask, cpu_mask, &cpu_online_map);
-        dest = cpu_mask_to_apicid(mask);
-
-        msg->address_hi = MSI_ADDR_BASE_HI;
-        msg->address_lo =
-            MSI_ADDR_BASE_LO |
-            ((INT_DEST_MODE == 0) ?
-             MSI_ADDR_DESTMODE_PHYS:
-             MSI_ADDR_DESTMODE_LOGIC) |
-            ((INT_DELIVERY_MODE != dest_LowestPrio) ?
-             MSI_ADDR_REDIRECTION_CPU:
-             MSI_ADDR_REDIRECTION_LOWPRI) |
-            MSI_ADDR_DEST_ID(dest);
-        msg->dest32 = dest;
-
-        msg->data =
-            MSI_DATA_TRIGGER_EDGE |
-            MSI_DATA_LEVEL_ASSERT |
-            ((INT_DELIVERY_MODE != dest_LowestPrio) ?
-             MSI_DATA_DELIVERY_FIXED:
-             MSI_DATA_DELIVERY_LOWPRI) |
-            MSI_DATA_VECTOR(vector);
+        msg->dest32 = cpu_mask_to_apicid(mask);
     }
+
+    msg->address_hi = MSI_ADDR_BASE_HI;
+    msg->address_lo = MSI_ADDR_BASE_LO |
+                      (INT_DEST_MODE ? MSI_ADDR_DESTMODE_LOGIC
+                                     : MSI_ADDR_DESTMODE_PHYS) |
+                      ((INT_DELIVERY_MODE != dest_LowestPrio)
+                       ? MSI_ADDR_REDIRECTION_CPU
+                       : MSI_ADDR_REDIRECTION_LOWPRI) |
+                      MSI_ADDR_DEST_ID(msg->dest32);
+
+    msg->data = MSI_DATA_TRIGGER_EDGE |
+                MSI_DATA_LEVEL_ASSERT |
+                ((INT_DELIVERY_MODE != dest_LowestPrio)
+                 ? MSI_DATA_DELIVERY_FIXED
+                 : MSI_DATA_DELIVERY_LOWPRI) |
+                MSI_DATA_VECTOR(vector);
 }
 
 static bool_t read_msi_msg(struct msi_desc *entry, struct msi_msg *msg)
diff --git a/xen/drivers/passthrough/vtd/iommu.c 
b/xen/drivers/passthrough/vtd/iommu.c
index 48f120b..b856ae1 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -1085,11 +1085,11 @@ static void dma_msi_set_affinity(struct irq_desc *desc, 
const cpumask_t *mask)
         return;
     }
 
-    msi_compose_msg(desc->arch.vector, desc->arch.cpu_mask, &msg);
-    /* Are these overrides really needed? */
+    msi_compose_msg(desc->arch.vector, NULL, &msg);
+    msg.dest32 = dest;
     if (x2apic_enabled)
         msg.address_hi = dest & 0xFFFFFF00;
-    msg.address_lo &= ~MSI_ADDR_DEST_ID_MASK;
+    ASSERT(!(msg.address_lo & MSI_ADDR_DEST_ID_MASK));
     msg.address_lo |= MSI_ADDR_DEST_ID(dest);
     iommu->msi.msg = msg;
 
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.8

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