The VT-d spec requires (10.4.4 Global Command Register, GCMD_REG General
Description) that:
If multiple control fields in this register need to be modified, software
must serialize the modifications through multiple writes to this register.
However, in irq_remapping.c, modifications of IRE and CFI are done in one
write. We need to do two separate writes with STS checking after each.
Fixes: af8d102f999a4 ("x86/intel/irq_remapping: Clean up x2apic opt-out
security warning mess")
Cc: Andy Lutomirski <l...@amacapital.net>
Cc: Jacob Pan <jacob.jun....@linux.intel.com>
Cc: Kevin Tian <kevin.t...@intel.com>
Cc: Ashok Raj <ashok....@intel.com>
Signed-off-by: Lu Baolu <baolu...@linux.intel.com>
---
drivers/iommu/intel/irq_remapping.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
Change log:
v1->v2:
- v1 posted here
https://lore.kernel.org/linux-iommu/20200826025825.2322-1-baolu...@linux.intel.com/;
- Add status check before disabling CFI. (Kevin)
diff --git a/drivers/iommu/intel/irq_remapping.c
b/drivers/iommu/intel/irq_remapping.c
index 9564d23d094f..7552bb7e92c8 100644
--- a/drivers/iommu/intel/irq_remapping.c
+++ b/drivers/iommu/intel/irq_remapping.c
@@ -507,12 +507,19 @@ static void iommu_enable_irq_remapping(struct intel_iommu
*iommu)
/* Enable interrupt-remapping */
iommu->gcmd |= DMA_GCMD_IRE;
- iommu->gcmd &= ~DMA_GCMD_CFI; /* Block compatibility-format MSIs */
writel(iommu->gcmd, iommu->reg + DMAR_GCMD_REG);
-
IOMMU_WAIT_OP(iommu, DMAR_GSTS_REG,
readl, (sts & DMA_GSTS_IRES), sts);
+ /* Block compatibility-format MSIs */
+ sts = readl(iommu->reg + DMAR_GSTS_REG);
+ if (sts & DMA_GSTS_CFIS) {
+ iommu->gcmd &= ~DMA_GCMD_CFI;
+ writel(iommu->gcmd, iommu->reg + DMAR_GCMD_REG);
+ IOMMU_WAIT_OP(iommu, DMAR_GSTS_REG,
+ readl, !(sts & DMA_GSTS_CFIS), sts);
+ }
+
/*
* With CFI clear in the Global Command register, we should be
* protected from dangerous (i.e. compatibility) interrupts
--
2.17.1
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