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

[Jordan Crouse <jordan@cosmicpenguin.net>]

On Tue, Mar 02, 2021 at 12:17:24PM +0000, Robin Murphy wrote:
> 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@codeaurora.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?

Agreed. The GPU doesn't use it and I doubt anything else would either since the
SMMU device is opaque to the leaf driver.

Jordan

> 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);
> > 
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