Hi, On 8/27/20 1:39 PM, Tian, Kevin wrote:
From: Lu Baolu <[email protected]> Sent: Thursday, August 27, 2020 12:25 PMThe 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 <[email protected]> Cc: Jacob Pan <[email protected]> Cc: Kevin Tian <[email protected]> Cc: Ashok Raj <[email protected]> Signed-off-by: Lu Baolu <[email protected]> --- 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- [email protected]/; - 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);no need of this readl as the status is already three in IOMMU_WAIT_OP.
Yes. Really! Best regards, baolu
+ 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
