[Xen-changelog] [xen master] VT-d: use two 32-bit writes to update DMAR fault address registers

[patchbot@xxxxxxx]

commit c99775d597fae9b8b8b27827b3d7845c49a2a0d7
Author:     Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
AuthorDate: Fri Feb 23 10:59:31 2018 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Feb 23 10:59:31 2018 +0100

    VT-d: use two 32-bit writes to update DMAR fault address registers
    
    The 64-bit DMAR fault address is composed of two 32 bits registers
    DMAR_FEADDR_REG and DMAR_FEUADDR_REG. According to VT-d spec:
    "Software is expected to access 32-bit registers as aligned doublewords",
    a hypervisor should use two 32-bit writes to DMAR_FEADDR_REG and
    DMAR_FEUADDR_REG separately in order to update a 64-bit fault address,
    rather than a 64-bit write to DMAR_FEADDR_REG. Note that when x2APIC
    is not enabled DMAR_FEUADDR_REG is reserved and it's not necessary to
    update it.
    
    Though I haven't seen any errors caused by such one 64-bit write on
    real machines, it's still better to follow the specification.
    
    Fixes: ae05fd3912b ("VT-d: use qword MMIO access for MSI address writes")
    Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Acked-by: Kevin Tian <kevin.tian@xxxxxxxxx>
---
 xen/drivers/passthrough/vtd/iommu.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/xen/drivers/passthrough/vtd/iommu.c 
b/xen/drivers/passthrough/vtd/iommu.c
index daaed0a..08bce92 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -1105,7 +1105,13 @@ static void dma_msi_set_affinity(struct irq_desc *desc, 
const cpumask_t *mask)
 
     spin_lock_irqsave(&iommu->register_lock, flags);
     dmar_writel(iommu->reg, DMAR_FEDATA_REG, msg.data);
-    dmar_writeq(iommu->reg, DMAR_FEADDR_REG, msg.address);
+    dmar_writel(iommu->reg, DMAR_FEADDR_REG, msg.address_lo);
+    /*
+     * When x2APIC is not enabled, DMAR_FEUADDR_REG is reserved and
+     * it's not necessary to update it.
+     */
+    if ( x2apic_enabled )
+        dmar_writel(iommu->reg, DMAR_FEUADDR_REG, msg.address_hi);
     spin_unlock_irqrestore(&iommu->register_lock, flags);
 }
 
--
generated by git-patchbot for /home/xen/git/xen.git#master

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