From: Robin Murphy <robin.murphy@arm.com>
To: Will Deacon <will@kernel.org>,
iommu@lists.linux-foundation.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 09/10] iommu/io-pgtable-arm: Rationalise TCR handling
Date: Fri, 22 Nov 2019 15:51:26 +0000 [thread overview]
Message-ID: <6e14584c-6942-b3b5-5691-faec4fc345f1@arm.com> (raw)
In-Reply-To: <20191120151142.GA26714@willie-the-truck>
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 :/
Robin.
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next prev parent reply other threads:[~2019-11-22 15:51 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-25 18:08 [PATCH v2 00/10] iommu/io-pgtable: Cleanup and prep for split tables Robin Murphy
2019-10-25 18:08 ` [PATCH v2 01/10] iommu/io-pgtable: Make selftest gubbins consistently __init Robin Murphy
2019-10-25 18:08 ` [PATCH v2 02/10] iommu/io-pgtable-arm: Rationalise size check Robin Murphy
2019-10-25 18:08 ` [PATCH v2 03/10] iommu/io-pgtable-arm: Simplify bounds checks Robin Murphy
2019-10-25 18:08 ` [PATCH v2 04/10] iommu/io-pgtable-arm: Simplify start level lookup Robin Murphy
2019-10-25 18:08 ` [PATCH v2 05/10] iommu/io-pgtable-arm: Simplify PGD size handling Robin Murphy
2019-10-25 18:08 ` [PATCH v2 06/10] iommu/io-pgtable-arm: Simplify level indexing Robin Murphy
2019-11-04 18:17 ` Will Deacon
2019-11-04 18:36 ` Robin Murphy
2019-11-04 19:20 ` Will Deacon
2019-10-25 18:08 ` [PATCH v2 07/10] iommu/io-pgtable-arm: Rationalise MAIR handling Robin Murphy
2019-11-04 18:20 ` Will Deacon
2019-11-04 18:43 ` Robin Murphy
2019-11-04 19:20 ` Will Deacon
2019-11-04 19:57 ` Will Deacon
2019-10-25 18:08 ` [PATCH v2 08/10] iommu/io-pgtable-arm: Rationalise TTBRn handling Robin Murphy
2019-10-28 15:09 ` Steven Price
2019-10-28 18:51 ` Robin Murphy
2019-11-04 18:36 ` Will Deacon
2019-11-04 19:12 ` Robin Murphy
2019-11-22 22:40 ` Jordan Crouse
2019-10-25 18:08 ` [PATCH v2 09/10] iommu/io-pgtable-arm: Rationalise TCR handling Robin Murphy
2019-11-04 19:14 ` Will Deacon
2019-11-04 23:27 ` Jordan Crouse
2019-11-20 15:11 ` Will Deacon
2019-11-22 15:51 ` Robin Murphy [this message]
2019-11-25 7:58 ` Will Deacon
2019-11-22 22:03 ` Jordan Crouse
2019-10-25 18:08 ` [PATCH v2 10/10] iommu/io-pgtable-arm: Prepare for TTBR1 usage Robin Murphy
2019-11-04 23:40 ` Jordan Crouse
2019-11-20 19:18 ` Will Deacon
2019-11-22 22:03 ` Jordan Crouse
2019-11-04 19:22 ` [PATCH v2 00/10] iommu/io-pgtable: Cleanup and prep for split tables Will Deacon
2019-11-04 20:20 ` Will Deacon
2020-01-10 15:09 ` Will Deacon
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