Messages in this thread Patch in this message | | | From | Lu Baolu <> | Subject | [PATCH v2 1/1] iommu/vt-d: Serialize IOMMU GCMD register modifications | Date | Thu, 27 Aug 2020 12:25:13 +0800 |
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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 <luto@amacapital.net> Cc: Jacob Pan <jacob.jun.pan@linux.intel.com> Cc: Kevin Tian <kevin.tian@intel.com> Cc: Ashok Raj <ashok.raj@intel.com> Signed-off-by: Lu Baolu <baolu.lu@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.lu@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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