[Xen-changelog] [xen stable-4.6] vt-d: fix IM bit mask and unmask of Fault Event Control Register

[patchbot@xxxxxxx]

commit 6307ebcbd7d3c2db3adb087d1d614b97cb5e64cc
Author:     Quan Xu <quan.xu@xxxxxxxxx>
AuthorDate: Mon Sep 28 17:38:09 2015 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Sep 28 17:38:09 2015 +0200

    vt-d: fix IM bit mask and unmask of Fault Event Control Register
    
    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.
    
    Signed-off-by: Quan Xu <quan.xu@xxxxxxxxx>
    Acked-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>
    Release-acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
    
    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>
    master commit: 86f3ff9fc4cc3cb69b96c1de74bcc51f738fe2b9
    master date: 2015-09-25 09:08:22 +0200
    master commit: 26b300bd727ef00a8f60329212a83c3b027a48f7
    master date: 2015-09-25 18:03:04 +0200
---
 xen/drivers/passthrough/vtd/iommu.c |   15 ++++++++++++---
 1 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/xen/drivers/passthrough/vtd/iommu.c 
b/xen/drivers/passthrough/vtd/iommu.c
index b67b624..dd13865 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -991,10 +991,13 @@ static void dma_msi_unmask(struct irq_desc *desc)
 {
     struct iommu *iommu = desc->action->dev_id;
     unsigned long flags;
+    u32 sts;
 
     /* unmask it */
     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);
     iommu->msi.msi_attrib.host_masked = 0;
 }
@@ -1003,10 +1006,13 @@ static void dma_msi_mask(struct irq_desc *desc)
 {
     unsigned long flags;
     struct iommu *iommu = desc->action->dev_id;
+    u32 sts;
 
     /* mask it */
     spin_lock_irqsave(&iommu->register_lock, flags);
-    dmar_writel(iommu->reg, DMAR_FECTL_REG, DMA_FECTL_IM);
+    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);
     iommu->msi.msi_attrib.host_masked = 1;
 }
@@ -2006,6 +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.  
@@ -2019,7 +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#stable-4.6

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