linux-kernel - Re: [PATCH 3/3] x86/iommu: use __GFP

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:	Sun, 28 Sep 2008 21:34:36 +0200
From:	Joerg Roedel <joerg.roedel@....com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	mingo@...hat.com, tglx@...utronix.de, hpa@...or.com,
	linux-kernel@...r.kernel.org, fujita.tomonori@....ntt.co.jp
Subject: Re: [PATCH 3/3] x86/iommu: use __GFP_ZERO instead of memset for GART

On Sat, Sep 27, 2008 at 08:18:55PM +0200, Ingo Molnar wrote:
> 
> another thing:
> 
> How hard would it be to add an CONFIG_IOMMU_DEBUG option that forces as 
> many DMA requests to go via the IOMMU as possible?
> 
> This slows things down of course so it's only for debugging - but it 
> also makes sure that we utilize the IOMMU code to the maximum - which is 
> not normally the case.
> 
> Would be nice to have it .config driven (default-disabled), so that 
> -tip's randconfig testing can stumble upon it every now and then. I've 
> got GART test-systems - this way we could find certain types of IOMMU 
> breakages sooner.

For AMD IOMMU I disabled the round-robin allocator to stress-test the
code. This means that the address allocation bitmap is always traversed
from the first bit. In consequence the TLB flushing is stressed a lot
(both in hardware and software) because the same DMA addresses are used
again and again. For testing I hardcoded it into the driver but I can
also make it depend on CONFIG_IOMMU_DEBUG.

Joerg

-- 
           |           AMD Saxony Limited Liability Company & Co. KG
 Operating |         Wilschdorfer Landstr. 101, 01109 Dresden, Germany
 System    |                  Register Court Dresden: HRA 4896
 Research  |              General Partner authorized to represent:
 Center    |             AMD Saxony LLC (Wilmington, Delaware, US)
           | General Manager of AMD Saxony LLC: Dr. Hans-R. Deppe, Thomas McCoy

--
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/