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Wed, 02 Jul 2025 16:54:51 -0700 (PDT) Received: from [192.168.1.14] ([38.175.170.29]) by smtp.gmail.com with ESMTPSA id 8926c6da1cb9f-50204a93102sm3155321173.104.2025.07.02.16.54.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 02 Jul 2025 16:54:51 -0700 (PDT) Message-ID: <1a13cf53-ffed-4521-917e-9c2856a5e348@linuxfoundation.org> Date: Wed, 2 Jul 2025 17:54:50 -0600 Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] usbip: convert to use faux_device To: Zongmin Zhou , Greg KH Cc: shuah@kernel.org, valentina.manea.m@gmail.com, i@zenithal.me, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, zhouzongmin@kylinos.cn, Shuah Khan References: <2a327b520760271471717fff9b222cdc34967489.1746662386.git.zhouzongmin@kylinos.cn> <20250604065410.76069-1-min_halo@163.com> <2025061926-paycheck-footnote-a2b8@gregkh> <2025062010-hardiness-flashily-cb0f@gregkh> <9d95bb75-586c-48dc-9e34-432cc13fd99f@163.com> <2025062004-navy-emboss-4743@gregkh> <2e0bbc5a-e74a-4fb5-884c-686dbaf99caf@linuxfoundation.org> <48ab511e-2847-4daa-98de-a234b8584b78@163.com> Content-Language: en-US From: Shuah Khan In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 7/1/25 20:12, Zongmin Zhou wrote: > > On 2025/7/2 06:56, Shuah Khan wrote: >> On 6/23/25 21:21, Zongmin Zhou wrote: >>> >>> On 2025/6/21 01:26, Shuah Khan wrote: >>>> On 6/20/25 03:27, Greg KH wrote: >>>>> On Fri, Jun 20, 2025 at 05:19:33PM +0800, Zongmin Zhou wrote: >>>>>> >>>>>> On 2025/6/20 12:29, Greg KH wrote: >>>>>>> On Fri, Jun 20, 2025 at 10:16:16AM +0800, Zongmin Zhou wrote: >>>>>>>> On 2025/6/19 19:01, Greg KH wrote: >>>>>>>>> On Wed, Jun 04, 2025 at 02:54:10PM +0800, Zongmin Zhou wrote: >>>>>>>>>> From: Zongmin Zhou >>>>>>>>>> >>>>>>>>>> The vhci driver does not need to create a platform device, >>>>>>>>>> it only did so because it was simple to do that in order to >>>>>>>>>> get a place in sysfs to hang some device-specific attributes. >>>>>>>>>> Now the faux device interface is more appropriate,change it >>>>>>>>>> over to use the faux bus instead. >>>>>>>>>> >>>>>>>>>> Signed-off-by: Zongmin Zhou >>>>>>>>>> --- >>>>>>>>>> Changes in v2: >>>>>>>>>> - don't change faux create api,just call probe on vhci_hcd_init. >>>>>>>>>> >>>>>>>>>>     drivers/usb/usbip/vhci.h             |  4 +- >>>>>>>>>>     drivers/usb/usbip/vhci_hcd.c         | 86 +++++++++++----------------- >>>>>>>>>>     drivers/usb/usbip/vhci_sysfs.c       | 68 +++++++++++----------- >>>>>>>>>>     tools/usb/usbip/libsrc/vhci_driver.h |  2 +- >>>>>>>>>>     4 files changed, 72 insertions(+), 88 deletions(-) >>>>>>>>> I get the following build errors from this patch: >>>>>>>>> >>>>>>>>> drivers/usb/usbip/vhci_hcd.c:1462:12: error: ‘vhci_hcd_resume’ defined but not used [-Werror=unused-function] >>>>>>>>>     1462 | static int vhci_hcd_resume(struct faux_device *fdev) >>>>>>>>>          |            ^~~~~~~~~~~~~~~ >>>>>>>>> drivers/usb/usbip/vhci_hcd.c:1418:12: error: ‘vhci_hcd_suspend’ defined but not used [-Werror=unused-function] >>>>>>>>>     1418 | static int vhci_hcd_suspend(struct faux_device *fdev, pm_message_t state) >>>>>>>>>          |            ^~~~~~~~~~~~~~~~ >>>>>>>>> cc1: all warnings being treated as errors >>>>>>>>> >>>>>>>>> Are you sure you tested this? >>>>>>>> I apologize for not enabling -Werror, which resulted in missing this error >>>>>>>> warning. >>>>>>>> I have tested usbip feature use the new patch,but not test system >>>>>>>> suspend/resume. >>>>>>>> The faux bus type don't add pm function,and vhci-hcd driver can't register >>>>>>>> it. >>>>>>>> Maybe have to add suspend/resume for it.like below: >>>>>>>> static const struct bus_type faux_bus_type = { >>>>>>>>       .name        = "faux", >>>>>>>>       .match        = faux_match, >>>>>>>>       .probe        = faux_probe, >>>>>>>>       .remove        = faux_remove, >>>>>>>>       .resume     = faux_resume, >>>>>>>>       .suspend    = faux_suspend, >>>>>>>> }; >>>>>>>> >>>>>>>> Is that right? >>>>>>>> Your expertise would be greatly valued. >>>>>>> As this is not real hardware, why do you need the suspend/resume >>>>>>> callbacks at all?  What is happening here that requires them? >>>>>> @greg, >>>>>> The vhci_hcd_suspend/vhci_hcd_resume interfaces are not designed for this >>>>>> faux device, but rather to >>>>>> manipulate the HCD_FLAG_HW_ACCESSIBLE bit in the hcd flags associated with >>>>>> the faux device. >>>>>> For example: >>>>>> During system standby: clear_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags) >>>>>> During system wakeup: set_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags) >>>>>> >>>>>> Previously, these two functions were registered through platform_driver, >>>>>> but faux bus does not have the relevant interface, so they were not called, >>>>>> resulting in this compilation warning error. >>>>>> >>>>>> This raises the question: Should the faux bus implement PM-related >>>>>> interface? >>>>>> I'm uncertain whether these functions are essential for the vhci-hcd driver >>>>>> or if they can be safely removed. >>>>>> >>>>>> However, during system standby/wakeup tests with remote USB devices bound to >>>>>> the vhci-hcd driver, >>>>>> I observed consistent failure scenarios across both the original platform >>>>>> bus and faux bus patch implementations. >>>> >>>> suspend and resume hooks have been in the code from beginning >>>> in the CONFIG_PM path. The original authors are skeptical about >>>> what should happen during suspend" >>>> >>>> /* what should happen for USB/IP under suspend/resume? */ >>>> suspend hook checks for active connections and sends EBBUSY >>>> back to pm core. >>>> >>>> Active connection means any of the ports are in USB_PORT_STAT_CONNECTION >>>> state. So as long as there are active connections between vhci client >>>> and the host, suspend won't work. So we really don't know what happens >>>> to the active connections if there are no suspend/resume hooks. >>>> >>>> If there are no active connections, then it will clear the HCD_FLAG_HW_ACCESSIBLE >>>> bit and returns to pm core to continue with suspend. >>>> >>>> resume sets the HCD_FLAG_HW_ACCESSIBLE flag to indicate hardware is accessible >>>> and initiates port status poll. >>>> >>>> - suspend hook prevents suspend >>>> >>>> With faux device since there is no suspend and resume hook, I would expect >>>> these hooks are not a factor in suspend and resume. >>>> >>>> vhci_hcd is a special case virtual driver as it is a proxy for controlling >>>> hardware on the host. >>>> >>>> Zongmin, >>>> >>>> Do suspend/resume work when vhci_hcd is not loaded? >>>> What happens when when system suspends and resumes with faux device? >>>> Can you send me dmesg logs and pm logs? >>>> >>> Hi Greg,shuah >>> >>> Yes, system with vhci_hcd unload or just load vhci_hcd driver >>> without usbip devices bound to vhci_hcd,system suspend/resume worked well. >>> Some logs for you. >> >> Sorry for the delay. I was at a conference last week. >> Thank you for sending these logs. >> >>> 1.system with vhci_hcd driver load,but don't bound any usbip devices to vhci_hcd,suspend/resume worked well. >>> see dmesg-faux bus-load.log >> >> >>> >>> 2.usbip device bound to vhci_hcd,and do system suspend action,suspend/resume worked failed. >>> I observed two distinct failure scenario: >>> Scenario 1: System failed to enter suspend state,and will auto resume; >> >> >>> the log for use platform bus: >>> dmesg-platform bus-device bound-auto resume.log >> >> This is clear from the suspend hook in the vhci_hcd. >> When it returns EBUSY, suspend will fail and move to >> auto resume. >> >>> the log for use faux bus: >>> dmesg-faux bus-device bound-auto resume.log >> >> It is good that the behavior is same with faux bus even though >> suspend hook isn't called. I will take a look at the log. >> >>> >>> Scenario 2: System resume failed with black screen freeze,a forced restart of the machine is require. >>> the log for use platform bus: >>> dmesg-platform bus-device bound-black screen.log >>> the log for use faux bus: >>> dmesg-faux bus-device bound-black screen.log >> >> That is bad. When does this happen? Is there a difference in >> configuration? >> > No, there's no difference. The same code is used for two different failure scenarios. > I just tested many times. These two different situations occur probabilistically. > But they both happened only when the USBIP device is bound to the vhci_hcd driver. >> The behavior same for platform bus and faux bus. Sounds like >> an existing problem that needs to be debugged separately. >> >> I will take a look at all these logs and get back to you in >> a day or two. >> I looked at the logs and here is what I found: Scenario 1: dmesg-faux bus-device bound-auto resume.log dmesg-platform bus-device bound-auto resume.log In this case suspend bailed out way before driver suspend when vhci_hcd is using platform and faux bus. Freezing remaining freezable tasks failed after 20.006 seconds (0 tasks refusing to freeze, wq_busy=1) Restarting kernel threads ... done OOM killer enabled. Restarting tasks ... done. random: crng reseeded on system resumption PM: suspend exit Auto-resume of the user-space worked. Scenario 1 isn't really interesting. Scenario 2: dmesg-faux bus-device bound-black screen.log dmesg-platform bus-device bound-black screen.log Even though the result is the same in seeing blank screen, how we get there is different. ================= faux-bus device: ================= - suspend worked - looks like usb 4-1: PM: calling usb_dev_suspend @ 6054, parent: usb4 usb 4-1: PM: usb_dev_suspend returned 0 after 13675 usecs usb usb4: PM: calling usb_dev_suspend @ 6055, parent: vhci_hcd.0 usb usb4: PM: usb_dev_suspend returned 0 after 9 usecs vhci_hcd suspend isn't in play here. usb_dev_suspend() returns. See below usb 4-1: PM: usb_dev_suspend returned message. ------------------------------------------------------------- - resume started (assuming it has been initiated by user) [ 650.027491][ T6056] pci 0000:00:01.0: PM: pci_pm_suspend_noirq returned 0 after 304 usecs See see timestamp difference between the last suspend message and the first resume message. [ 674.000257][ T39] pci 0000:00:00.0: PM: calling pci_pm_resume_noirq @ 39, parent: pci0000:00 usb 4-1 usb_dev_resume never returns. [ 674.071125][ T6117] usb usb4: PM: usb_dev_resume returned 0 after 21110 usecs [ 674.113991][ T6126] usb 4-1: PM: calling usb_dev_resume @ 6126, parent: usb4 ------------------------------------------------------------- ===================== platform bus device ===================== - suspend was aborted because vhci_hcd suspend routine returned error [ 297.854621][ T9402] usb 4-1: PM: calling usb_dev_suspend @ 9402, parent: usb4 [ 297.868524][ T9402] usb 4-1: PM: usb_dev_suspend returned 0 after 13214 usecs [ 297.869994][ T9403] usb usb4: PM: calling usb_dev_suspend @ 9403, parent: vhci_hcd.0 [ 297.871959][ T9403] usb usb4: PM: usb_dev_suspend returned 0 after 30 usecs [ 297.873644][ T9394] vhci_hcd vhci_hcd.0: PM: calling platform_pm_suspend @ 9394, parent: platform [ 297.874738][ T9394] vhci_hcd vhci_hcd.0: We have 1 active connection. Do not suspend. [ 297.875369][ T9394] vhci_hcd vhci_hcd.0: PM: dpm_run_callback(): platform_pm_suspend returns -16 [ 297.876078][ T9394] vhci_hcd vhci_hcd.0: PM: platform_pm_suspend returned -16 after 1341 usecs [ 297.876774][ T9394] vhci_hcd vhci_hcd.0: PM: failed to suspend: error -16 - the following triggers resume [ 297.877321][ T9394] PM: Some devices failed to suspend, or early wake event detected [ 297.881065][ T9403] usb usb3: PM: usb_dev_resume returned 0 after 19 usecs [ 297.904551][ T9408] usb usb4: PM: usb_dev_resume returned 0 after 22911 usecs [ 297.905148][ T9418] usb 4-1: PM: calling usb_dev_resume @ 9418, parent: usb4 usb 4-1 usb_dev_resume never returns. Note - In both cases, usb_dev_resume doesn't return. When it is called is the difference. I don't think suspend/resume works when devices are bound. Suspend exits and starts resume which seems to fail because it doesn't handle the virtual usb device resume. There is a missing piece here. When vhci_hcd imports a device and acts as a proxy between the virtual mass storage device (e.g in this case) - it appears suspend and resume are handled as if it is a usb device. Maybe this is incorrect? usb_dev_suspend() works and usb_dev_resume() on these virtual usb devices? Do we need to handle this in usb_dev_resume()? Talking out loud - I have to do some looking into. thanks, -- Shuah