On Fri, Nov 22, 2019 at 03:51:26PM +0000, Robin Murphy wrote: > On 20/11/2019 3:11 pm, Will Deacon wrote: > > On Mon, Nov 04, 2019 at 04:27:56PM -0700, Jordan Crouse wrote: > > > On Mon, Nov 04, 2019 at 07:14:45PM +0000, Will Deacon wrote: > > > > On Fri, Oct 25, 2019 at 07:08:38PM +0100, Robin Murphy wrote: > > > > > diff --git a/drivers/iommu/qcom_iommu.c b/drivers/iommu/qcom_iommu.c > > > > > index 9a57eb6c253c..059be7e21030 100644 > > > > > --- a/drivers/iommu/qcom_iommu.c > > > > > +++ b/drivers/iommu/qcom_iommu.c > > > > > @@ -271,15 +271,13 @@ static int qcom_iommu_init_domain(struct > > > > > iommu_domain *domain, > > > > > iommu_writeq(ctx, ARM_SMMU_CB_TTBR0, > > > > > pgtbl_cfg.arm_lpae_s1_cfg.ttbr | > > > > > FIELD_PREP(TTBRn_ASID, ctx->asid)); > > > > > - iommu_writeq(ctx, ARM_SMMU_CB_TTBR1, > > > > > - FIELD_PREP(TTBRn_ASID, ctx->asid)); > > > > > + iommu_writeq(ctx, ARM_SMMU_CB_TTBR1, 0); > > > > > > > > Are you sure it's safe to drop the ASID here? Just want to make sure > > > > there > > > > wasn't some "quirk" this was helping with. > > > > > > I was reminded of this recently. Some of our SMMU guys told me that a 0x0 > > > in > > > TTBR1 could cause a S2 fault if a faulty transaction caused a ttbr1 > > > lookup so > > > the "quirk" was writing the ASID so the register wasn't zero. I'm not > > > sure if > > > this is a vendor specific blip or not. > > > > You should be able to set EPD1 to prevent walks via TTBR1 in that case, > > though. Sticking the ASID in there is still dodgy if EPD1 is clear and > > TTBR1 points at junk (or even physical address 0x0). > > > > That's probably something which should be folded into this patch. > > Note that EPD1 was being set by io-pgtable-arm before this patch, and > remains set by virtue of arm_smmu_lpae_tcr() afterwards, so presumably the > brokenness might run a bit deeper than that. Either way, though, I'm > somewhat dubious since the ASID could well be 0 anyway :/
Ah, I missed that the qcom driver was calling arm_smmu_lpae_tcr() with your patches. In which case, everything should be fine, no? Will _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
