Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: 5.10 regression, many XHCI swiotlb buffer is full / DMAR: Device
 bounce map failed errors on thunderbolt connected XHCI controller
To:     Christoph Hellwig <hch@lst.de>
Cc:     Mathias Nyman <mathias.nyman@intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-usb <linux-usb@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-pci@vger.kernel.org
References: <b046dd04-ac4f-3c69-0602-af810fb1b365@redhat.com>
 <be031d15-201f-0e5c-8b0f-be030077141f@redhat.com>
 <20201124102715.GA16983@lst.de>
From:   Hans de Goede <hdegoede@redhat.com>
Message-ID: <f1bd62b4-a746-6b1c-08ee-6dd1982722b6@redhat.com>
Date:   Tue, 24 Nov 2020 11:31:02 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101
 Thunderbird/78.4.0
MIME-Version: 1.0
In-Reply-To: <20201124102715.GA16983@lst.de>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk

Hi,

On 11/24/20 11:27 AM, Christoph Hellwig wrote:
> On Mon, Nov 23, 2020 at 03:49:09PM +0100, Hans de Goede wrote:
>> Hi,
>>
>> +Cc Christoph Hellwig <hch@lst.de>
>>
>> Christoph, this is still an issue, so I've been looking around a bit and think this
>> might have something to do with the dma-mapping-5.10 changes.
>>
>> Do you have any suggestions to debug this, or is it time to do a git bisect
>> on this before 5.10 ships with regression?
> 
> Given that DMAR prefix this seems to be about using intel-iommu + bounce
> buffering for external devices.  I can't really think of anything specific
> in 5.10 related to that, so maybe you'll need to bisect.
> 
> I doub this means we are actually leaking swiotlb buffers, so while
> I'm pretty sure we broke something in lower layers this also means
> xhci doesn't handle swiotlb operation very gracefully in general.

Ok, I've re-arranged my schedule a bit so that I have time to bisect this
tomorrow, so with some luck I will be able to provide info on which commit
introduced this issue tomorrow around the end of the day.

Regards,

Hans