linux-kernel - Re: [PATCH] pci: print out DMA mask info

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]

Date:	Fri, 10 Oct 2008 16:45:08 -0600
From:	Grant Grundler <grundler@...isc-linux.org>
To:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
Cc:	yinghai@...nel.org, grundler@...isc-linux.org, matthew@....cx,
	jbarnes@...tuousgeek.org, mingo@...e.hu, tglx@...utronix.de,
	hpa@...or.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH] pci: print out DMA mask info

On Fri, Oct 10, 2008 at 11:40:56AM +0900, FUJITA Tomonori wrote:
> IIRC, except for one SGI architecture, coherent_dma_mask is
> meaningless, dma_mask is always equal to coherent_dma_mask.

Not correct. Several PCI-X devices can only do 32-bit DMA to control
data but can do 64-bit DMA for payload data. I don't have the list off
the top of my head but that is the origin of coherent DMA mask.

> Lots of
> IOMMU implementations ignore coherent_dma_mask and use dma_mask for
> alloc_coherent().

That sounds like a bug. And I don't think it's "lots".

> Some drivers don't set up coherent_dma_mask.

They probably should. Current default is 32-bits for PCI devices.

> Theoretically, we need to fix this but it doesn't cause any
> problem. That's why nobody cares about it, I guess.

Agreed - for the "supported" configurations, it works.

hth,
grant
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/