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

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Message-ID: <CAF6AEGsCbYDsLLPdVdJHdQbd9xrO==UMWMQVkwhuG8gdp3gd+g@mail.gmail.com>
Date:   Tue, 11 May 2021 11:59:33 -0700
From:   Rob Clark <robdclark@...il.com>
To:     Robin Murphy <robin.murphy@....com>,
        Jordan Crouse <jcrouse@...eaurora.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        "list@....net:IOMMU DRIVERS <iommu@...ts.linux-foundation.org>, Joerg
        Roedel <joro@...tes.org>," <iommu@...ts.linux-foundation.org>,
        Will Deacon <will@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 1/3] iommu/arm-smmu: Add support for driver IOMMU fault handlers

On Tue, Mar 2, 2021 at 7:54 AM Jordan Crouse <jordan@...micpenguin.net> wrote:
>
> 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@...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?
>
> Agreed. The GPU doesn't use it and I doubt anything else would either since the
> SMMU device is opaque to the leaf driver.

Looks like other iommu drivers use a fun mix of attached device (for
ones that can make assumptions about one device per domain) and the
iommu dev ptr.. probably NULL is the right answer..

BR,
-R

> 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);
> > >
> > _______________________________________________
> > iommu mailing list
> > iommu@...ts.linux-foundation.org
> > https://lists.linuxfoundation.org/mailman/listinfo/iommu
> _______________________________________________
> iommu mailing list
> iommu@...ts.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu

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