[Xen-changelog] [xen master] vt-d: fix IM bit unmask of Fault Event Control Register in init_vtd_hw()

[patchbot@xxxxxxx]

commit 26b300bd727ef00a8f60329212a83c3b027a48f7
Author:     Quan Xu <quan.xu@xxxxxxxxx>
AuthorDate: Fri Sep 25 18:03:04 2015 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Sep 25 18:03:04 2015 +0200

    vt-d: fix IM bit unmask of Fault Event Control Register in init_vtd_hw()
    
    Bit 0:29 in Fault Event Control Register are 'Reserved and Preserved',
    software cannot write 0 to it unconditionally. Software must preserve
    the value read for writes.
    
    Suggested-by: Jan Beulich <jbeulich@xxxxxxxx>
    Signed-off-by: Quan Xu <quan.xu@xxxxxxxxx>
---
 xen/drivers/passthrough/vtd/iommu.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/xen/drivers/passthrough/vtd/iommu.c 
b/xen/drivers/passthrough/vtd/iommu.c
index 1d8b561..8254937 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -2012,6 +2012,7 @@ static int init_vtd_hw(void)
     struct iommu_flush *flush = NULL;
     int ret;
     unsigned long flags;
+    u32 sts;
 
     /*
      * Basic VT-d HW init: set VT-d interrupt, clear VT-d faults.  
@@ -2025,7 +2026,9 @@ static int init_vtd_hw(void)
         clear_fault_bits(iommu);
 
         spin_lock_irqsave(&iommu->register_lock, flags);
-        dmar_writel(iommu->reg, DMAR_FECTL_REG, 0);
+        sts = dmar_readl(iommu->reg, DMAR_FECTL_REG);
+        sts &= ~DMA_FECTL_IM;
+        dmar_writel(iommu->reg, DMAR_FECTL_REG, sts);
         spin_unlock_irqrestore(&iommu->register_lock, flags);
     }
 
--
generated by git-patchbot for /home/xen/git/xen.git#master

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