linux-kernel - Re: [PATCH v7u1 26/31] x86: Don't enable swiotlb if there is not enough ram for it

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Date:	Sat, 5 Jan 2013 15:04:12 -0700
From:	Shuah Khan <shuahkhan@...il.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>, Jan Kiszka <jan.kiszka@....de>,
	Jason Wessel <jason.wessel@...driver.com>,
	linux-kernel@...r.kernel.org,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH v7u1 26/31] x86: Don't enable swiotlb if there is not
 enough ram for it

On Fri, Jan 4, 2013 at 9:10 PM, Yinghai Lu <yinghai@...nel.org> wrote:
> On Fri, Jan 4, 2013 at 6:02 PM, Shuah Khan <shuahkhan@...il.com> wrote:
>> I applied your patch to 3.6.11 and changed the panic() to pr_info()
>> and also changed enough_mem_for_swiotlb() to always return false to
>> simulate not enough memory condition as this system does have enough
>> memory.
>>
>> So at least on this AMD system, your patch will result in a panic.
>
> ok, thanks for testing.
>
> if enough_mem_for_swiotlb() return false really,  allocating buffer
> for swiotlb with bootmem would panic already, right?
>
> so this patch just delay the panic a while for AMD system with
> unhandled devices by IOMMU.
>
> Thanks
>
> Yinghai

Right. It will eventually panic. I think this is not a valid test. I
am planning to run more tests without forcing no memory condition
which is what I should have done in the first place. I will let you
know what I find, very likely Monday.

Thanks,
-- Shuah
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