Messages in this thread | | | Subject | Re: [PATCH v2 1/3] iommu/arm-smmu: Add support for driver IOMMU fault handlers | From | Robin Murphy <> | Date | Fri, 22 Jan 2021 12:53:17 +0000 |
| |
On 2021-01-22 12:41, Will Deacon wrote: > On Tue, Nov 24, 2020 at 12:15:58PM -0700, 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 | 16 +++++++++++++--- >> 1 file changed, 13 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c >> index 0f28a8614da3..7fd18bbda8f5 100644 >> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c >> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c >> @@ -427,6 +427,7 @@ 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)) >> @@ -436,11 +437,20 @@ 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, >> + 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); >> + /* >> + * If the iommu fault returns an error (except -ENOSYS) then assume that >> + * they will handle resuming on their own >> + */ >> + if (!ret || ret == -ENOSYS) >> + arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_FSR, fsr); > > Hmm, I don't grok this part. If the fault handler returned an error and > we don't clear the FSR, won't we just re-take the irq immediately?
If we don't touch the FSR at all, yes. Even if we clear the fault indicator bits, the interrupt *might* remain asserted until a stalled transaction is actually resolved - that's that lovely IMP-DEF corner.
Robin.
> I think > it would be better to do this unconditionally, and print the "Unhandled > context fault" message for any non-zero value of ret. > > Will >
| |