From: "Petr Tesařík" <petr@tesarici.cz>
To: Christoph Hellwig <hch@lst.de>
Cc: Will Deacon <will@kernel.org>,
linux-kernel@vger.kernel.org, kernel-team@android.com,
iommu@lists.linux.dev,
Marek Szyprowski <m.szyprowski@samsung.com>,
Robin Murphy <robin.murphy@arm.com>,
Petr Tesarik <petr.tesarik1@huawei-partners.com>,
Dexuan Cui <decui@microsoft.com>
Subject: Re: [PATCH 2/2] swiotlb: Enforce page alignment in swiotlb_alloc()
Date: Mon, 29 Jan 2024 08:43:26 +0100 [thread overview]
Message-ID: <20240129084326.4667af6a@meshulam.tesarici.cz> (raw)
In-Reply-To: <20240129060853.GB19258@lst.de>
On Mon, 29 Jan 2024 07:08:53 +0100
Christoph Hellwig <hch@lst.de> wrote:
> On Fri, Jan 26, 2024 at 03:19:56PM +0000, Will Deacon wrote:
> > diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> > index 25febb9e670c..92433ea9f2d2 100644
> > --- a/kernel/dma/swiotlb.c
> > +++ b/kernel/dma/swiotlb.c
> > @@ -1647,6 +1647,12 @@ struct page *swiotlb_alloc(struct device *dev, size_t size)
> > return NULL;
> >
> > tlb_addr = slot_addr(pool->start, index);
> > + if (!PAGE_ALIGNED(tlb_addr)) {
> > + dev_WARN_ONCE(dev, 1, "Cannot return 'struct page *' for non page-aligned swiotlb addr 0x%pa.\n",
> > + &tlb_addr);
> > + swiotlb_release_slots(dev, tlb_addr);
> > + return NULL;
> > + }
> >
> > return pfn_to_page(PFN_DOWN(tlb_addr));
>
> So PFN_DOWN aligns the address and thus per se converting the unaligned
> address isn't a problem. That being said swiotlb obviously should never
> allocate unaligned addresses, but the placement of this check feels
> odd to me. Also because it only catches swiotlb_alloc and not the
> map side.
We may have to rethink how alignment constraints are interpreted. See
also my reply to PATCH 1/2.
> Maybe just throw a WARN_ON_ONCE into slot_addr() ?
Yes.
Or, what if I write a KUnit test suite for swiotlb to combat this
constant stream of various regressions?
Petr T
next prev parent reply other threads:[~2024-01-29 7:43 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-26 15:19 [PATCH 0/2] Fix double allocation in swiotlb_alloc() Will Deacon
2024-01-26 15:19 ` [PATCH 1/2] swiotlb: Fix allocation alignment requirement when searching slots Will Deacon
2024-01-26 17:01 ` Petr Tesařík
2024-01-29 19:32 ` Will Deacon
2024-01-29 20:40 ` Petr Tesařík
2024-01-29 22:05 ` Will Deacon
2024-01-26 15:19 ` [PATCH 2/2] swiotlb: Enforce page alignment in swiotlb_alloc() Will Deacon
2024-01-26 16:23 ` Petr Tesařík
2024-01-29 19:35 ` Will Deacon
2024-01-29 6:08 ` Christoph Hellwig
2024-01-29 7:43 ` Petr Tesařík [this message]
2024-01-29 7:50 ` Christoph Hellwig
2024-01-29 19:49 ` Will Deacon
2024-01-30 14:34 ` Christoph Hellwig
2024-01-26 16:20 ` [PATCH 0/2] Fix double allocation " Petr Tesařík
2024-01-29 18:42 ` Will Deacon
2024-01-29 19:26 ` Petr Tesařík
2024-01-29 19:33 ` 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=20240129084326.4667af6a@meshulam.tesarici.cz \
--to=petr@tesarici.cz \
--cc=decui@microsoft.com \
--cc=hch@lst.de \
--cc=iommu@lists.linux.dev \
--cc=kernel-team@android.com \
--cc=linux-kernel@vger.kernel.org \
--cc=m.szyprowski@samsung.com \
--cc=petr.tesarik1@huawei-partners.com \
--cc=robin.murphy@arm.com \
--cc=will@kernel.org \
/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).