On Wed, Mar 12, 2025 at 6:05 AM Will Deacon <will@xxxxxxxxxx> wrote:
>
> On Tue, Mar 11, 2025 at 06:36:38PM -0400, Connor Abbott wrote:
> > On Tue, Mar 11, 2025 at 2:06 PM Will Deacon <will@xxxxxxxxxx> wrote:
> > >
> > > On Tue, Mar 04, 2025 at 11:56:47AM -0500, Connor Abbott wrote:
> > > > This will be used by drm/msm for GPU page faults, replacing the manual
> > > > register reading it does.
> > > >
> > > > Signed-off-by: Connor Abbott <cwabbott0@xxxxxxxxx>
> > > > ---
> > > > drivers/iommu/arm/arm-smmu/arm-smmu-qcom-debug.c | 4 ++--
> > > > drivers/iommu/arm/arm-smmu/arm-smmu.c | 27 +++++++++++++-----------
> > > > drivers/iommu/arm/arm-smmu/arm-smmu.h | 5 ++++-
> > > > 3 files changed, 21 insertions(+), 15 deletions(-)
> > > >
> > > > diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom-debug.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom-debug.c
> > > > index 548783f3f8e89fd978367afa65c473002f66e2e7..ae4fdbbce6ba80440f539557a39866a932360d4e 100644
> > > > --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom-debug.c
> > > > +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom-debug.c
> > > > @@ -400,7 +400,7 @@ irqreturn_t qcom_smmu_context_fault(int irq, void *dev)
> > > >
> > > > if (list_empty(&tbu_list)) {
> > > > ret = report_iommu_fault(&smmu_domain->domain, NULL, cfi.iova,
> > > > - cfi.fsynr & ARM_SMMU_CB_FSYNR0_WNR ? IOMMU_FAULT_WRITE : IOMMU_FAULT_READ);
> > > > + cfi.fsynr0 & ARM_SMMU_CB_FSYNR0_WNR ? IOMMU_FAULT_WRITE : IOMMU_FAULT_READ);
> > > >
> > > > if (ret == -ENOSYS)
> > > > arm_smmu_print_context_fault_info(smmu, idx, &cfi);
> > > > @@ -412,7 +412,7 @@ irqreturn_t qcom_smmu_context_fault(int irq, void *dev)
> > > > phys_soft = ops->iova_to_phys(ops, cfi.iova);
> > > >
> > > > tmp = report_iommu_fault(&smmu_domain->domain, NULL, cfi.iova,
> > > > - cfi.fsynr & ARM_SMMU_CB_FSYNR0_WNR ? IOMMU_FAULT_WRITE : IOMMU_FAULT_READ);
> > > > + cfi.fsynr0 & ARM_SMMU_CB_FSYNR0_WNR ? IOMMU_FAULT_WRITE : IOMMU_FAULT_READ);
> > > > if (!tmp || tmp == -EBUSY) {
> > > > ret = IRQ_HANDLED;
> > > > resume = ARM_SMMU_RESUME_TERMINATE;
> > > > diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > > > index ade4684c14c9b2724a71e2457288dbfaf7562c83..a9213e0f1579d1e3be0bfba75eea1d5de23117de 100644
> > > > --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > > > +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > > > @@ -409,9 +409,12 @@ void arm_smmu_read_context_fault_info(struct arm_smmu_device *smmu, int idx,
> > > > struct arm_smmu_context_fault_info *cfi)
> > > > {
> > > > cfi->iova = arm_smmu_cb_readq(smmu, idx, ARM_SMMU_CB_FAR);
> > > > + cfi->ttbr0 = arm_smmu_cb_readq(smmu, idx, ARM_SMMU_CB_TTBR0);
> > > > cfi->fsr = arm_smmu_cb_read(smmu, idx, ARM_SMMU_CB_FSR);
> > > > - cfi->fsynr = arm_smmu_cb_read(smmu, idx, ARM_SMMU_CB_FSYNR0);
> > > > + cfi->fsynr0 = arm_smmu_cb_read(smmu, idx, ARM_SMMU_CB_FSYNR0);
> > > > + cfi->fsynr1 = arm_smmu_cb_read(smmu, idx, ARM_SMMU_CB_FSYNR1);
> > >
> > > We already have an implementation hook (->get_fault_info()) which the
> > > qcom SMMU driver can override with qcom_adreno_smmu_get_fault_info().
> > > That thing dumps these registers already so if we're moving that into
> > > the core SMMU driver, let's get rid of the hook and move everybody over
> > > rather than having it done in both places.
> >
> > As you probably saw, the next commit moves over
> > qcom_adreno_smmu_get_fault_info() to use this. The current back door
> > used by drm/msm to access these functions is specific to adreno_smmu
> > and there isn't an equivalent interface to allow it to call a generic
> > SMMU function so it isn't possible to move it entirely to the core. At
> > least not without a bigger refactoring that isn't justified for this
> > series that is just trying to fix things.
>
> Ok :(
>
> > > > cfi->cbfrsynra = arm_smmu_gr1_read(smmu, ARM_SMMU_GR1_CBFRSYNRA(idx));
> > > > + cfi->contextidr = arm_smmu_cb_read(smmu, idx, ARM_SMMU_CB_CONTEXTIDR);
> > >
> > > I think the CONTEXTIDR register is stage-1 only, so we shouldn't dump
> > > it for stage-2 domains.
> > >
> > Does it matter if we read the register though, as long as users are
> > aware of this and don't use its value for anything?
>
> I think the contents are "UNKNOWN", so it could be hugely confusing even
> if they just got logged someplace. Why is it difficult to avoid touching
> it for stage-2?
>
> Will
Fwiw, we are only ever using stage-1
BR,
-R
