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: <CAE9FiQX-OxTzt3BPh3nSLQxDUBGR=eKob5AqXYzy=Lw9NYTaGw@mail.gmail.com>
Date:	Wed, 9 Jan 2013 13:15:06 -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 1:00 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.

Thanks

Yinghai
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