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* [PATCH] iommu/arm-smmu-v3: prevent corruption of ste stage-1 context ptr
@ 2016-12-19 20:38 Nate Watterson
  2016-12-20  9:53 ` Will Deacon
  0 siblings, 1 reply; 3+ messages in thread
From: Nate Watterson @ 2016-12-19 20:38 UTC (permalink / raw)
  To: Will Deacon, Robin Murphy, Joerg Roedel, linux-arm-kernel, iommu,
	linux-kernel
  Cc: Nate Watterson

To ensure that the stage-1 context ptr for an ste points to the
intended context descriptor, this patch adds code to clear away
the stale context ptr value prior to or'ing in the new one.

Signed-off-by: Nate Watterson <nwatters@codeaurora.org>
---
 drivers/iommu/arm-smmu-v3.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 4d6ec44..093f9f1 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -1080,6 +1080,8 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_device *smmu, u32 sid,
 		if (smmu->features & ARM_SMMU_FEAT_STALLS)
 			dst[1] |= cpu_to_le64(STRTAB_STE_1_S1STALLD);
 
+		val &= ~(STRTAB_STE_0_S1CTXPTR_MASK <<
+			 STRTAB_STE_0_S1CTXPTR_SHIFT);
 		val |= (ste->s1_cfg->cdptr_dma & STRTAB_STE_0_S1CTXPTR_MASK
 		        << STRTAB_STE_0_S1CTXPTR_SHIFT) |
 			STRTAB_STE_0_CFG_S1_TRANS;
-- 
Qualcomm Datacenter Technologies, Inc. on behalf of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux
Foundation Collaborative Project.

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] iommu/arm-smmu-v3: prevent corruption of ste stage-1 context ptr
  2016-12-19 20:38 [PATCH] iommu/arm-smmu-v3: prevent corruption of ste stage-1 context ptr Nate Watterson
@ 2016-12-20  9:53 ` Will Deacon
  2016-12-21  4:11   ` [PATCH] iommu/arm-smmu-v3: Clear prior settings when updating STEs Nate Watterson
  0 siblings, 1 reply; 3+ messages in thread
From: Will Deacon @ 2016-12-20  9:53 UTC (permalink / raw)
  To: Nate Watterson
  Cc: Robin Murphy, Joerg Roedel, linux-arm-kernel, iommu, linux-kernel

Hi Nate,

Thanks for the patch.

On Mon, Dec 19, 2016 at 03:38:38PM -0500, Nate Watterson wrote:
> To ensure that the stage-1 context ptr for an ste points to the
> intended context descriptor, this patch adds code to clear away
> the stale context ptr value prior to or'ing in the new one.
> 
> Signed-off-by: Nate Watterson <nwatters@codeaurora.org>
> ---
>  drivers/iommu/arm-smmu-v3.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index 4d6ec44..093f9f1 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -1080,6 +1080,8 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_device *smmu, u32 sid,
>  		if (smmu->features & ARM_SMMU_FEAT_STALLS)
>  			dst[1] |= cpu_to_le64(STRTAB_STE_1_S1STALLD);
>  
> +		val &= ~(STRTAB_STE_0_S1CTXPTR_MASK <<
> +			 STRTAB_STE_0_S1CTXPTR_SHIFT);
>  		val |= (ste->s1_cfg->cdptr_dma & STRTAB_STE_0_S1CTXPTR_MASK
>  		        << STRTAB_STE_0_S1CTXPTR_SHIFT) |
>  			STRTAB_STE_0_CFG_S1_TRANS;

Good catch. We only clear the Config field at present, although I think
it would be better if we just did val = 0 instead of clearing the Config
field, and then just recreate all of the S1-related fields (ctxptr, fmt,
cdmax) if we're installing a stage-1 STE. The other STE fields aren't
treated as read-modify-write, so it's more consistent not to treat the
initial dword specially other than for determining ste_live.

What do you think?

Will

^ permalink raw reply	[flat|nested] 3+ messages in thread

* [PATCH] iommu/arm-smmu-v3: Clear prior settings when updating STEs
  2016-12-20  9:53 ` Will Deacon
@ 2016-12-21  4:11   ` Nate Watterson
  0 siblings, 0 replies; 3+ messages in thread
From: Nate Watterson @ 2016-12-21  4:11 UTC (permalink / raw)
  To: Will Deacon, Robin Murphy, Joerg Roedel, linux-arm-kernel, iommu,
	linux-kernel
  Cc: Nate Watterson

To prevent corruption of the stage-1 context pointer field when
updating STEs, rebuild the entire containing dword instead of
clearing individual fields.

Signed-off-by: Nate Watterson <nwatters@codeaurora.org>
---
 drivers/iommu/arm-smmu-v3.c | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 4d6ec44..94f305d 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -1042,13 +1042,8 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_device *smmu, u32 sid,
 		}
 	}
 
-	/* Nuke the existing Config, as we're going to rewrite it */
-	val &= ~(STRTAB_STE_0_CFG_MASK << STRTAB_STE_0_CFG_SHIFT);
-
-	if (ste->valid)
-		val |= STRTAB_STE_0_V;
-	else
-		val &= ~STRTAB_STE_0_V;
+	/* Nuke the existing STE_0 value, as we're going to rewrite it */
+	val = ste->valid ? STRTAB_STE_0_V : 0;
 
 	if (ste->bypass) {
 		val |= disable_bypass ? STRTAB_STE_0_CFG_ABORT
@@ -1083,7 +1078,6 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_device *smmu, u32 sid,
 		val |= (ste->s1_cfg->cdptr_dma & STRTAB_STE_0_S1CTXPTR_MASK
 		        << STRTAB_STE_0_S1CTXPTR_SHIFT) |
 			STRTAB_STE_0_CFG_S1_TRANS;
-
 	}
 
 	if (ste->s2_cfg) {
-- 
Qualcomm Datacenter Technologies, Inc. on behalf of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux
Foundation Collaborative Project.

^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2016-12-21  4:15 UTC | newest]

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2016-12-19 20:38 [PATCH] iommu/arm-smmu-v3: prevent corruption of ste stage-1 context ptr Nate Watterson
2016-12-20  9:53 ` Will Deacon
2016-12-21  4:11   ` [PATCH] iommu/arm-smmu-v3: Clear prior settings when updating STEs Nate Watterson

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