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 4/4] iommu/io-pgtable-arm: Prepare for TTBR1 usage
Date: Tue, 20 Aug 2019 16:58:24 +0100 [thread overview]
Message-ID: <20190820155823.ptn2rfvnmkd4v632@willie-the-truck> (raw)
In-Reply-To: <469dc66a-2532-5f7f-cd8d-3fe13f6c279a@arm.com>
On Tue, Aug 20, 2019 at 03:51:45PM +0100, Robin Murphy wrote:
> On 20/08/2019 11:30, Will Deacon wrote:
> > On Mon, Aug 19, 2019 at 07:19:31PM +0100, Robin Murphy wrote:
> > > Now that callers are free to use a given table for TTBR1 if they wish
> > > (all they need do is shift the provided attributes when constructing
> > > their final TCR value), the only remaining impediment is the address
> > > validation on map/unmap. The fact that the LPAE address space split is
> > > symmetric makes this easy to accommodate - by simplifying the current
> > > range checks into explicit tests that address bits above IAS are all
> > > zero, it then follows straightforwardly to add the inverse test to
> > > allow the all-ones case as well.
> > >
> > > Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> > > ---
> > > drivers/iommu/io-pgtable-arm.c | 7 ++++---
> > > 1 file changed, 4 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
> > > index 09cb20671fbb..f39c50356351 100644
> > > --- a/drivers/iommu/io-pgtable-arm.c
> > > +++ b/drivers/iommu/io-pgtable-arm.c
> > > @@ -475,13 +475,13 @@ static int arm_lpae_map(struct io_pgtable_ops *ops, unsigned long iova,
> > > arm_lpae_iopte *ptep = data->pgd;
> > > int ret, lvl = ARM_LPAE_START_LVL(data);
> > > arm_lpae_iopte prot;
> > > + long iaext = (long)iova >> data->iop.cfg.ias;
> > > /* If no access, then nothing to do */
> > > if (!(iommu_prot & (IOMMU_READ | IOMMU_WRITE)))
> > > return 0;
> > > - if (WARN_ON(iova >= (1ULL << data->iop.cfg.ias) ||
> > > - paddr >= (1ULL << data->iop.cfg.oas)))
> > > + if (WARN_ON((iaext && ~iaext) || paddr >> data->iop.cfg.oas))
> >
> > I had to read that '&&' twice, but I see what you're doing now :)
> >
> > > return -ERANGE;
> >
> > This doesn't seem sufficient to prevent a mixture of TTBR1 and TTBR0
> > addresses from being mapped in the same TTBR. Perhaps we need a quirk for
> > TTBR1, which could then take care of setting EPDx appropriately?
>
> Right, that's the one downside of going for the minimalist "io-pgtable
> doesn't even have to know" approach. On reflection, though, in that paradigm
> it should probably be the caller's responsibility to convert TTBR1 addresses
> to preserve the "as if TTBR0" illusion anyway :/
Right, and I'd rather not push stuff into the caller for the common case.
It's not exactly onerous to support this in io-pgtable. It's also why I'd
still like to keep the EPDx in there, because the callers that care can
rewrite the stuff, but at least we provided a default.
> The advantage of not having a quirk is that it allows split address spaces
> to fit more closely with the aux_domain idea, i.e. we could allocate and
> initialise a domain without having to assume, or even care, whether it will
> end up attached as a primary or aux domain. It *might* even be potentially
> useful to have a domain attached to TTBR0 of one device's context and TTBR1
> of another's at the same time, although that's pretty niche.
That sounds pretty theoretical to me at the moment.
Will
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
prev parent reply other threads:[~2019-08-20 15:58 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-19 18:19 [PATCH 0/4] iommu/io-pgtable: Cleanup and prep for split tables Robin Murphy
2019-08-19 18:19 ` [PATCH 1/4] iommu/io-pgtable-arm: Rationalise MAIR handling Robin Murphy
2019-08-19 18:19 ` [PATCH 2/4] iommu/io-pgtable-arm: Rationalise TTBRn handling Robin Murphy
2019-08-20 10:19 ` Will Deacon
2019-08-20 14:17 ` Robin Murphy
2019-08-20 15:50 ` Will Deacon
2019-08-19 18:19 ` [PATCH 3/4] iommu/io-pgtable-arm: Rationalise TCR handling Robin Murphy
2019-08-20 10:31 ` Will Deacon
2019-08-20 15:25 ` Robin Murphy
2019-08-20 16:07 ` Will Deacon
2019-08-20 18:41 ` Robin Murphy
2019-08-21 12:11 ` Will Deacon
2019-08-21 12:56 ` Robin Murphy
2019-10-03 17:33 ` Jordan Crouse
2019-10-24 10:51 ` Will Deacon
2019-10-24 11:23 ` Robin Murphy
2019-10-24 11:40 ` Will Deacon
2019-08-20 16:23 ` Jordan Crouse
2019-08-19 18:19 ` [PATCH 4/4] iommu/io-pgtable-arm: Prepare for TTBR1 usage Robin Murphy
2019-08-19 22:34 ` Jordan Crouse
2019-08-20 13:51 ` Robin Murphy
2019-08-20 10:30 ` Will Deacon
2019-08-20 14:51 ` Robin Murphy
2019-08-20 15:58 ` Will Deacon [this message]
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=20190820155823.ptn2rfvnmkd4v632@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).