On 4/5/2018 5:26 AM, Will Deacon wrote:
> On Wed, Mar 28, 2018 at 09:39:40AM -0500, Timur Tabi wrote:
>> From: Sameer Goel <sg...@codeaurora.org>
>>
>> Set SMMU_GBPA to abort all incoming translations during the SMMU reset
>> when SMMUEN==0.
>>
>> This prevents a race condition where a stray DMA from the crashed primary
>> kernel can try to access an IOVA address as an invalid PA when SMMU is
>> disabled during reset in the crash kernel.
>>
>> Signed-off-by: Sameer Goel <sg...@codeaurora.org>
>> ---
>>  drivers/iommu/arm-smmu-v3.c | 12 ++++++++++++
>>  1 file changed, 12 insertions(+)
>>
>> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
>> index 3f2f1fc68b52..c04a89310c59 100644
>> --- a/drivers/iommu/arm-smmu-v3.c
>> +++ b/drivers/iommu/arm-smmu-v3.c
>> @@ -2458,6 +2458,18 @@ static int arm_smmu_device_reset(struct 
>> arm_smmu_device *smmu, bool bypass)
>>      if (reg & CR0_SMMUEN)
>>              dev_warn(smmu->dev, "SMMU currently enabled! Resetting...\n");
>>  
>> +    /*
>> +     * Abort all incoming translations. This can happen in a kdump case
>> +     * where SMMU is initialized when a prior DMA is pending. Just
>> +     * disabling the SMMU in this case might result in writes to invalid
>> +     * PAs.
>> +     */
>> +    ret = arm_smmu_update_gbpa(smmu, 1, GBPA_ABORT);
>> +    if (ret) {
>> +            dev_err(smmu->dev, "GBPA not responding to update\n");
>> +            return ret;
>> +    }
> 
> This needs to be predicated on the disable_bypass option, otherwise I think
> it will cause regressions for systems that rely on passthrough.
Ok, I'll make the change.
> 
> Will
> 

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