linux-kernel - Re: [PATCH 06/10] swiotlb: use swiotlb_map_page in swiotlb_map_sg

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Message-ID: <CALAqxLVSDkv4faF3ta_ue9AA9s8B=-8cAMxC_sow+wZYtrfxeQ@mail.gmail.com>
Date:   Mon, 12 Nov 2018 16:07:03 -0800
From:   John Stultz <john.stultz@...aro.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Robin Murphy <robin.murphy@....com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        iommu@...ts.linux-foundation.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Valentin Schneider <valentin.schneider@....com>
Subject: Re: [PATCH 06/10] swiotlb: use swiotlb_map_page in swiotlb_map_sg_attrs

On Thu, Nov 8, 2018 at 11:49 PM, Christoph Hellwig <hch@....de> wrote:
> On Tue, Nov 06, 2018 at 05:27:14PM -0800, John Stultz wrote:
>> But at that point if I just re-apply "swiotlb: use swiotlb_map_page in
>> swiotlb_map_sg_attrs", I reproduce the hangs.
>>
>> Any suggestions for how to further debug what might be going wrong
>> would be appreciated!
>
> Very odd.  In the end map_sg and map_page are defined to do the same
> things to start with.  The only real issue we had in this area was:
>
> "[PATCH v2] of/device: Really only set bus DMA mask when appropriate"
>
> so with current mainline + that you still see a problem, and if you
> rever the commit we are replying to it still goes away?

Just to confirm, as of 4.20-rc2 (which includes the of/device patch
above), I'm still seeing this issue, but it isn't as reliable to
reproduce as before.

With "swiotlb: use swiotlb_map_page in swiotlb_map_sg_attrs" reverted
(along with the dependent swiotlb patches) it doesn't seem to trigger
(no matter what I try).  But re-applying that patch it tends to
trigger by itself at boot up, but sometimes I have to run "find /" to
trigger the io hang/stall.

thanks
-john