iommu.lists.linux-foundation.org archive mirror
 help / color / mirror / Atom feed
From: Will Deacon <will@kernel.org>
To: Robin Murphy <robin.murphy@arm.com>
Cc: 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: Mon, 25 Nov 2019 07:58:22 +0000	[thread overview]
Message-ID: <20191125075821.GB1809@willie-the-truck> (raw)
In-Reply-To: <6e14584c-6942-b3b5-5691-faec4fc345f1@arm.com>

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

  reply	other threads:[~2019-11-25  7:58 UTC|newest]

Thread overview: 34+ 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
     [not found]       ` <20191120151142.GA26714@willie-the-truck>
2019-11-22 15:51         ` Robin Murphy
2019-11-25  7:58           ` Will Deacon [this message]
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20191125075821.GB1809@willie-the-truck \
    --to=will@kernel.org \
    --cc=iommu@lists.linux-foundation.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=robin.murphy@arm.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).