linux-kernel - Re: [PATCH 1/2] xen/swiotlb: relax alignment requirements

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <f6822b63-ebda-4134-b91e-b189006d072a@suse.com>
Date: Wed, 12 Feb 2025 12:04:24 +0100
From: Jürgen Groß <jgross@...e.com>
To: Jan Beulich <jbeulich@...e.com>
Cc: Stefano Stabellini <sstabellini@...nel.org>,
 Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
 xen-devel@...ts.xenproject.org, Jan Vejvalka <jan.vejvalka@...otol.cuni.cz>,
 linux-kernel@...r.kernel.org, iommu@...ts.linux.dev
Subject: Re: [PATCH 1/2] xen/swiotlb: relax alignment requirements

On 12.02.25 07:53, Jan Beulich wrote:
> On 11.02.2025 13:04, Juergen Gross wrote:
>> When mapping a buffer for DMA via .map_page or .map_sg DMA operations,
>> there is no need to check the machine frames to be aligned according
>> to the mapped areas size. All what is needed in these cases is that the
>> buffer is contiguous at machine level.
> 
> Is this really true in all cases? Can't e.g. compound pages make it here,
> with the caller then still being permitted to assume higher than page
> alignment? Alignment checking in xen_swiotlb_map_page() would perhaps
> need doing with the base address of the incoming page, i.e. excluding
> the incoming offset.

The DMA interfaces in question (.map_page and .map_sg) are explicitly
designed for DMA streaming mode. I don't think streaming mode requires a
special page alignment.


Juergen

Download attachment "OpenPGP_0xB0DE9DD628BF132F.asc" of type "application/pgp-keys" (3684 bytes)

Download attachment "OpenPGP_signature.asc" of type "application/pgp-signature" (496 bytes)