Re: [PATCH v3 1/1] iommu/vt-d: Serialize IOMMU GCMD register modifications

2020-09-04 Thread Joerg Roedel 
On Fri, Aug 28, 2020 at 08:06:15AM +0800, Lu Baolu wrote:
> 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. It
> also checks the status register before writing command register to avoid
> unnecessary register write.
> 
> 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 | 10 --
>  1 file changed, 8 insertions(+), 2 deletions(-)

Applied for v5.9, thanks.

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RE: [PATCH v3 1/1] iommu/vt-d: Serialize IOMMU GCMD register modifications

2020-08-27 Thread Tian, Kevin 
> From: Lu Baolu 
> Sent: Friday, August 28, 2020 8:06 AM
> 
> 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. It
> also checks the status register before writing command register to avoid
> unnecessary register write.
> 
> 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 | 10 --
>  1 file changed, 8 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)
> v2->v3:
>   - v2 posted here
> https://lore.kernel.org/linux-iommu/20200827042513.30292-1-
> baolu...@linux.intel.com/
>   - Remove unnecessary register read (Kevin)
> 
> diff --git a/drivers/iommu/intel/irq_remapping.c
> b/drivers/iommu/intel/irq_remapping.c
> index 9564d23d094f..a91dd997d268 100644
> --- a/drivers/iommu/intel/irq_remapping.c
> +++ b/drivers/iommu/intel/irq_remapping.c
> @@ -507,12 +507,18 @@ 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 */
> + 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

Reviewed-by: Kevin Tian 
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[PATCH v3 1/1] iommu/vt-d: Serialize IOMMU GCMD register modifications

2020-08-27 Thread Lu Baolu 
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. It
also checks the status register before writing command register to avoid
unnecessary register write.

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 | 10 --
 1 file changed, 8 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)
v2->v3:
  - v2 posted here

https://lore.kernel.org/linux-iommu/20200827042513.30292-1-baolu...@linux.intel.com/
  - Remove unnecessary register read (Kevin)

diff --git a/drivers/iommu/intel/irq_remapping.c 
b/drivers/iommu/intel/irq_remapping.c
index 9564d23d094f..a91dd997d268 100644
--- a/drivers/iommu/intel/irq_remapping.c
+++ b/drivers/iommu/intel/irq_remapping.c
@@ -507,12 +507,18 @@ 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 */
+   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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