linux-kernel - Re: [PATCH v2 2/2] usbip: Implement SG support to vhci

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Date:   Mon, 29 Jul 2019 10:32:31 -0600
From:   shuah <shuah@...nel.org>
To:     Suwan Kim <suwan.kim027@...il.com>
Cc:     valentina.manea.m@...il.com, stern@...land.harvard.edu,
        gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, shuah <shuah@...nel.org>
Subject: Re: [PATCH v2 2/2] usbip: Implement SG support to vhci

On 7/29/19 8:52 AM, Suwan Kim wrote:
> Hi Shuah,
> 
> On Tue, Jul 23, 2019 at 06:21:53PM -0600, shuah wrote:
>> Hi Suwan,
>>
>> On 7/5/19 10:43 AM, Suwan Kim wrote:
>>> There are bugs on vhci with usb 3.0 storage device. Originally, vhci
>>> doesn't supported SG, so USB storage driver on vhci breaks SG list
>>> into multiple URBs and it causes error that a transfer got terminated
>>> too early because the transfer length for one of the URBs was not
>>> divisible by the maxpacket size.
>>>
>>> In this patch, vhci basically support SG and it sends each SG list
>>> entry to the stub driver. Then, the stub driver sees the total length
>>> of the buffer and allocates SG table and pages according to the total
>>> buffer length calling sgl_alloc(). After the stub driver receives
>>> completed URB, it again sends each SG list entry to vhci.
>>>
>>> If HCD of the server doesn't support SG, the stub driver breaks a
>>> single SG reqeust into several URBs and submit them to the server's
>>> HCD. When all the split URBs are completed, the stub driver
>>> reassembles the URBs into a single return command and sends it to
>>> vhci.
>>>
>>> Signed-off-by: Suwan Kim <suwan.kim027@...il.com>
>>> ---
>>>    drivers/usb/usbip/stub.h         |   7 +-
>>>    drivers/usb/usbip/stub_main.c    |  52 +++++---
>>>    drivers/usb/usbip/stub_rx.c      | 207 ++++++++++++++++++++++---------
>>>    drivers/usb/usbip/stub_tx.c      | 108 +++++++++++-----
>>>    drivers/usb/usbip/usbip_common.c |  60 +++++++-- >   drivers/usb/usbip/vhci_hcd.c     |  10 +-
>>>    drivers/usb/usbip/vhci_tx.c      |  49 ++++++--
>>>    7 files changed, 372 insertions(+), 121 deletions(-)
>>
>> While you are working on v3 to fix chekpatch and other issues
>> I pointed out, I have more for you.
>>
>> What happens when you have mismatched server and client side?
>> i.e stub does and vhci doesn't and vice versa.
>>
>> Make sure to run checkpatch. Also check spelling errors in
>> comments and your commit log.
>>
>> I am not sure if your eeror paths are correct. Run usbip_test.sh
>>
>> tools/testing/selftests/drivers/usb/usbip
> 
> I don't know what mismatch you mentioned. Are you saying
> "match busid table" at the end of usbip_test.sh?
> How does it relate to SG support of this patch?
> Could you tell me more about the problem situation?
> 

What happens when usbip_host is running a kernel without the sg
support and vhci_hcd does? Just make sure this works with the
checks for sg support status as a one of your tests for this
sg feature.

Looking forward to seeing v3 soon!

thanks,
-- Shuah