From: shuah <shuah@kernel.org>
To: Suwan Kim <suwan.kim027@gmail.com>
Cc: valentina.manea.m@gmail.com, gregkh@linuxfoundation.org,
stern@rowland.harvard.edu, linux-usb@vger.kernel.org,
linux-kernel@vger.kernel.org, shuah <shuah@kernel.org>
Subject: Re: [PATCH v3 1/2] usbip: Skip DMA mapping and unmapping for urb at vhci
Date: Mon, 5 Aug 2019 09:08:18 -0600 [thread overview]
Message-ID: <8ce7b60c-6075-54ac-a917-921cb41003e6@kernel.org> (raw)
In-Reply-To: <20190805052358.GA8904@localhost.localdomain>
On 8/4/19 11:23 PM, Suwan Kim wrote:
> On Fri, Aug 02, 2019 at 04:22:27PM -0600, shuah wrote:
>> On 8/2/19 11:36 AM, Suwan Kim wrote:
>>> vhci doesn’t do DMA for remote device. Actually, the real DMA
>>> operation is done by network card driver. vhci just passes virtual
>>> address of the buffer to the network stack, so vhci doesn’t use and
>>> need dma address of the buffer of the URB.
>>>
>>> But HCD provides DMA mapping and unmapping function by default.
>>> Moreover, it causes unnecessary DMA mapping and unmapping which
>>> will be done again at the NIC driver and it wastes CPU cycles.
>>> So, implement map_urb_for_dma and unmap_urb_for_dma function for
>>> vhci in order to skip the DMA mapping and unmapping procedure.
>>>
>>> When it comes to supporting SG for vhci, it is useful to use native
>>> SG list (urb->num_sgs) instead of mapped SG list because DMA mapping
>>> fnuction can adjust the number of SG list (urb->num_mapped_sgs).
>>> And vhci_map_urb_for_dma() prevents isoc pipe from using SG as
>>> hcd_map_urb_for_dma() does.
>>>
>>> Signed-off-by: Suwan Kim <suwan.kim027@gmail.com>
>>> ---
>>> drivers/usb/usbip/vhci_hcd.c | 19 +++++++++++++++++++
>>> 1 file changed, 19 insertions(+)
>>>
>>> diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
>>> index 000ab7225717..c62f7fa8118c 100644
>>> --- a/drivers/usb/usbip/vhci_hcd.c
>>> +++ b/drivers/usb/usbip/vhci_hcd.c
>>> @@ -1288,6 +1288,22 @@ static int vhci_free_streams(struct usb_hcd *hcd, struct usb_device *udev,
>>> return 0;
>>> }
>>> +static int vhci_map_urb_for_dma(struct usb_hcd *hcd, struct urb *urb,
>>> + gfp_t mem_flags)
>>> +{
>>> + if (usb_endpoint_xfer_isoc(&urb->ep->desc) && urb->num_sgs) {
>>> + WARN_ON(1);
>>
>> Don't add WARN_ON. I cleaned them all up recently and don't want new
>> ones added.
>
> Ok. I will remove it and resend v4.
>
Please add appropriate error message in place of WARN_ON
thanks,
-- Shuah
next prev parent reply other threads:[~2019-08-05 15:08 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-02 17:36 [PATCH v3 0/2] usbip: Implement SG support Suwan Kim
2019-08-02 17:36 ` [PATCH v3 1/2] usbip: Skip DMA mapping and unmapping for urb at vhci Suwan Kim
2019-08-02 22:22 ` shuah
2019-08-05 5:23 ` Suwan Kim
2019-08-05 15:08 ` shuah [this message]
2019-08-02 17:36 ` [PATCH v3 2/2] usbip: Implement SG support to vhci-hcd and stub driver Suwan Kim
2019-08-02 22:41 ` shuah
2019-08-05 8:04 ` Suwan Kim
2019-08-05 15:07 ` shuah
2019-08-02 22:44 ` [PATCH v3 0/2] usbip: Implement SG support shuah
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=8ce7b60c-6075-54ac-a917-921cb41003e6@kernel.org \
--to=shuah@kernel.org \
--cc=gregkh@linuxfoundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-usb@vger.kernel.org \
--cc=stern@rowland.harvard.edu \
--cc=suwan.kim027@gmail.com \
--cc=valentina.manea.m@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).