[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20240126172059.48ad7b9f@meshulam.tesarici.cz>
Date: Fri, 26 Jan 2024 17:20:59 +0100
From: Petr Tesařík <petr@...arici.cz>
To: Will Deacon <will@...nel.org>
Cc: linux-kernel@...r.kernel.org, kernel-team@...roid.com,
iommu@...ts.linux.dev, Christoph Hellwig <hch@....de>, Marek Szyprowski
<m.szyprowski@...sung.com>, Robin Murphy <robin.murphy@....com>, Petr
Tesarik <petr.tesarik1@...wei-partners.com>, Dexuan Cui
<decui@...rosoft.com>
Subject: Re: [PATCH 0/2] Fix double allocation in swiotlb_alloc()
Hi Will,
On Fri, 26 Jan 2024 15:19:54 +0000
Will Deacon <will@...nel.org> wrote:
> Hi folks,
>
> These two patches fix a nasty double allocation problem in swiotlb_alloc()
> and add a diagnostic to help catch any similar issues in future. This was
> a royal pain to track down and I've had to make a bit of a leap at the
> correct alignment semantics (i.e. iotlb_align_mask vs alloc_align_mask).
Welcome to the club. I believe you had to re-discover what I described here:
https://lore.kernel.org/linux-iommu/20231108101347.77cab795@meshulam.tesarici.cz/
The relevant part would be this:
To sum it up, there are two types of alignment:
1. specified by a device's min_align_mask; this says how many low
bits of a buffer's physical address must be preserved,
2. specified by allocation size and/or the alignment parameter;
this says how many low bits in the first IO TLB slot's physical
address must be zero.
Fix for that has been sitting on my TODO list for too long. :-(
Petr T
> Without these changes, we've been observing random vsock hangs when
> communicating with virtual machines in Android.
>
> Please have a look!
>
> Cheers,
>
> Will
>
> Cc: iommu@...ts.linux.dev
> Cc: Christoph Hellwig <hch@....de>
> Cc: Marek Szyprowski <m.szyprowski@...sung.com>
> Cc: Robin Murphy <robin.murphy@....com>
> Cc: Petr Tesarik <petr.tesarik1@...wei-partners.com>
> Cc: Dexuan Cui <decui@...rosoft.com>
>
> --->8
>
> Will Deacon (2):
> swiotlb: Fix allocation alignment requirement when searching slots
> swiotlb: Enforce page alignment in swiotlb_alloc()
>
> kernel/dma/swiotlb.c | 32 ++++++++++++++++++++++----------
> 1 file changed, 22 insertions(+), 10 deletions(-)
>
Powered by blists - more mailing lists