Re: [PATCH v2 1/1] iommu/vt-d: Serialize IOMMU GCMD register modifications
Hi, On 8/27/20 1:39 PM, Tian, Kevin wrote: From: Lu Baolu Sent: Thursday, August 27, 2020 12:25 PM 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 Cc: Jacob Pan Cc: Kevin Tian Cc: Ashok Raj Signed-off-by: Lu Baolu --- 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); 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
RE: [PATCH v2 1/1] iommu/vt-d: Serialize IOMMU GCMD register modifications
> From: Lu Baolu > Sent: Thursday, August 27, 2020 12:25 PM > > 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 > Cc: Jacob Pan > Cc: Kevin Tian > Cc: Ashok Raj > Signed-off-by: Lu Baolu > --- > 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); no need of this readl as the status is already three in IOMMU_WAIT_OP. > + 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
[PATCH v2 1/1] iommu/vt-d: Serialize IOMMU GCMD register modifications
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 Cc: Jacob Pan Cc: Kevin Tian Cc: Ashok Raj Signed-off-by: Lu Baolu --- 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