linux-kernel - Re: [PATCH v3 1/3] iommu/arm-smmu: Add support for driver IOMMU fault handlers

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Date:   Tue, 2 Mar 2021 12:17:24 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Jordan Crouse <jcrouse@...eaurora.org>,
        linux-arm-msm@...r.kernel.org
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 1/3] iommu/arm-smmu: Add support for driver IOMMU fault
 handlers

On 2021-02-25 17:51, Jordan Crouse wrote:
> Call report_iommu_fault() to allow upper-level drivers to register their
> own fault handlers.
> 
> Signed-off-by: Jordan Crouse <jcrouse@...eaurora.org>
> ---
> 
>   drivers/iommu/arm/arm-smmu/arm-smmu.c | 9 +++++++--
>   1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> index d8c6bfde6a61..0f3a9b5f3284 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> @@ -408,6 +408,7 @@ static irqreturn_t arm_smmu_context_fault(int irq, void *dev)
>   	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
>   	struct arm_smmu_device *smmu = smmu_domain->smmu;
>   	int idx = smmu_domain->cfg.cbndx;
> +	int ret;
>   
>   	fsr = arm_smmu_cb_read(smmu, idx, ARM_SMMU_CB_FSR);
>   	if (!(fsr & ARM_SMMU_FSR_FAULT))
> @@ -417,8 +418,12 @@ static irqreturn_t arm_smmu_context_fault(int irq, void *dev)
>   	iova = arm_smmu_cb_readq(smmu, idx, ARM_SMMU_CB_FAR);
>   	cbfrsynra = arm_smmu_gr1_read(smmu, ARM_SMMU_GR1_CBFRSYNRA(idx));
>   
> -	dev_err_ratelimited(smmu->dev,
> -	"Unhandled context fault: fsr=0x%x, iova=0x%08lx, fsynr=0x%x, cbfrsynra=0x%x, cb=%d\n",
> +	ret = report_iommu_fault(domain, dev, iova,

Beware that "dev" here is not a struct device, so this isn't right. I'm 
not entirely sure what we *should* be passing here, since we can't 
easily attribute a context fault to a specific client device, and 
passing the IOMMU device seems a bit dubious too, so maybe just NULL?

Robin.

> +		fsynr & ARM_SMMU_FSYNR0_WNR ? IOMMU_FAULT_WRITE : IOMMU_FAULT_READ);
> +
> +	if (ret == -ENOSYS)
> +		dev_err_ratelimited(smmu->dev,
> +		"Unhandled context fault: fsr=0x%x, iova=0x%08lx, fsynr=0x%x, cbfrsynra=0x%x, cb=%d\n",
>   			    fsr, iova, fsynr, cbfrsynra, idx);
>   
>   	arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_FSR, fsr);
>