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

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Message-ID: <CAE9FiQVKFz6K8xw2Eu5J8G6=QDdo2A7Y2-81GYP5yvP+T1YG5A@mail.gmail.com>
Date:	Fri, 4 Jan 2013 12:34:51 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Shuah Khan <shuahkhan@...il.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Eric W. Biederman" <ebiederm@...ssion.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 9:50 AM, Shuah Khan <shuahkhan@...il.com> wrote:
>
> This change doesn't take into account what swiolb was when
> pci_swiotlb_detect_override() is called. Instead of returning
> use_swiotlb like the original code did, it returns swiotlb which could
> be zero, if !enough_mem_for_swiotlb().
>
> Might work fine on Intel platforms, but not on systems where the IOMMU
> driver wants to enable swiotlb for some devices as in the case of AMD.
>
> AMD IOMMU driver enables swiotlb for devices that are not specified in
> IVRs and/or not in the AMD IOMMU scope, after it successfully
> initializes IOMMU. It will explicitely set switolb=1 to make sure
> reserved swiotlb memory is not released. This change will break that
> case.

in that case, we have to panic....

please check attached patch.

Also for those kind of systems, users must specify crashkernel_low=72M or
what ever for kdump.

Thanks

Yinghai

Download attachment "auto_switch_off_swiotlb.patch" of type "application/octet-stream" (3429 bytes)