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: <CAE9FiQVsbDfLOyv=D4_BLtrKpp+Ydj7pren8Cu3rNGztbj=w=w@mail.gmail.com>
Date:	Thu, 10 Jan 2013 15:07:10 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Shuah Khan <shuahkhan@...il.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, 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 Wed, Jan 9, 2013 at 1:15 PM, Yinghai Lu <yinghai@...nel.org> wrote:
> On Wed, Jan 9, 2013 at 1:00 PM, Eric W. Biederman <ebiederm@...ssion.com> wrote:
>> Yinghai Lu <yinghai@...nel.org> writes:
>>
>>> please check updated attached. It should address all your request.
>>
>> There is one significant bug that I can see.
>>
>> swiotlb_print_info tests no_iotlb_memory but no_iotlb_memory is set
>> after swiotlb_init_with_tlb returns.
>
> there is another swiotlb_print_info calling from
> pci_swiotlb_late_init
>
> void __init pci_swiotlb_late_init(void)
> {
>         /* An IOMMU turned us off. */
>         if (!swiotlb)
>                 swiotlb_free();
>         else {
>                 printk(KERN_INFO "PCI-DMA: "
>                        "Using software bounce buffering for IO (SWIOTLB)\n");
>                 swiotlb_print_info();
>         }
> }
>
> so we need that checking when swiotlb == 1, but actually we can not
> allocate that before.

Eric, so the code is right to put checking in swiotlb_print_info ?

I'd like to post the whole patchset again and ask HPA to put them in tip/next
to catch -v3.9 merging window.

Thanks

Yinghai
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