Messages in this thread Patch in this message | | | Date | Tue, 2 May 2023 08:50:51 +0100 | Subject | Re: [PATCH v2 8/9] drm/fdinfo: Add comm/cmdline override fields | From | Tvrtko Ursulin <> |
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On 01/05/2023 17:58, Rob Clark wrote: > On Fri, Apr 28, 2023 at 4:05 AM Tvrtko Ursulin > <tvrtko.ursulin@linux.intel.com> wrote: >> >> >> On 27/04/2023 18:53, Rob Clark wrote: >>> From: Rob Clark <robdclark@chromium.org> >>> >>> These are useful in particular for VM scenarios where the process which >>> has opened to drm device file is just a proxy for the real user in a VM >>> guest. >>> >>> Signed-off-by: Rob Clark <robdclark@chromium.org> >>> --- >>> Documentation/gpu/drm-usage-stats.rst | 18 ++++++++++++++++++ >>> drivers/gpu/drm/drm_file.c | 15 +++++++++++++++ >>> include/drm/drm_file.h | 19 +++++++++++++++++++ >>> 3 files changed, 52 insertions(+) >>> >>> diff --git a/Documentation/gpu/drm-usage-stats.rst b/Documentation/gpu/drm-usage-stats.rst >>> index 58dc0d3f8c58..e4877cf8089c 100644 >>> --- a/Documentation/gpu/drm-usage-stats.rst >>> +++ b/Documentation/gpu/drm-usage-stats.rst >>> @@ -73,6 +73,24 @@ scope of each device, in which case `drm-pdev` shall be present as well. >>> Userspace should make sure to not double account any usage statistics by using >>> the above described criteria in order to associate data to individual clients. >>> >>> +- drm-comm-override: <valstr> >>> + >>> +Returns the client executable override string. Some drivers support letting >>> +userspace override this in cases where the userspace is simply a "proxy". >>> +Such as is the case with virglrenderer drm native context, where the host >>> +process is just forwarding command submission, etc, from guest userspace. >>> +This allows the proxy to make visible the executable name of the actual >>> +app in the VM guest. >>> + >>> +- drm-cmdline-override: <valstr> >>> + >>> +Returns the client cmdline override string. Some drivers support letting >>> +userspace override this in cases where the userspace is simply a "proxy". >>> +Such as is the case with virglrenderer drm native context, where the host >>> +process is just forwarding command submission, etc, from guest userspace. >>> +This allows the proxy to make visible the cmdline of the actual app in the >>> +VM guest. >> >> Perhaps it would be okay to save space here by not repeating the >> description, like: >> >> drm-comm-override: <valstr> >> drm-cmdline-override: <valstr> >> >> Long description blah blah... >> This allows the proxy to make visible the _executable name *and* command >> line_ blah blah.. >> >>> + >>> Utilization >>> ^^^^^^^^^^^ >>> >>> diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c >>> index 9321eb0bf020..d7514c313af1 100644 >>> --- a/drivers/gpu/drm/drm_file.c >>> +++ b/drivers/gpu/drm/drm_file.c >>> @@ -178,6 +178,8 @@ struct drm_file *drm_file_alloc(struct drm_minor *minor) >>> spin_lock_init(&file->master_lookup_lock); >>> mutex_init(&file->event_read_lock); >>> >>> + mutex_init(&file->override_lock); >>> + >>> if (drm_core_check_feature(dev, DRIVER_GEM)) >>> drm_gem_open(dev, file); >>> >>> @@ -292,6 +294,8 @@ void drm_file_free(struct drm_file *file) >>> WARN_ON(!list_empty(&file->event_list)); >>> >>> put_pid(file->pid); >>> + kfree(file->override_comm); >>> + kfree(file->override_cmdline); >>> kfree(file); >>> } >>> >>> @@ -995,6 +999,17 @@ void drm_show_fdinfo(struct seq_file *m, struct file *f) >>> PCI_SLOT(pdev->devfn), PCI_FUNC(pdev->devfn)); >>> } >>> >>> + mutex_lock(&file->override_lock); >> >> You could add a fast unlocked check before taking the mutex for no risk >> apart a transient false negative. For 99.9999% of userspace it would >> mean no pointless lock/unlock cycle. > > I'm not sure I get your point? This needs to be serialized against > userspace setting the override values
if (file->override_comm || file->override_cmdline) { mutex_lock(&file->override_lock); if (file->override_comm) drm_printf(&p, "drm-comm-override:\t%s\n", file->override_comm); if (file->override_cmdline) drm_printf(&p, "drm-cmdline-override:\t%s\n", file->override_cmdline); mutext_unlock(&file->override_lock); }
No risk apart for a transient false negative (which is immaterial for userspace since fdinfo reads are not ordered versus the override setting anyway) and 99.9% of deployments can get by not needing to pointlessly cycle the lock.
> >> >>> + if (file->override_comm) { >>> + drm_printf(&p, "drm-comm-override:\t%s\n", >>> + file->override_comm); >>> + } >>> + if (file->override_cmdline) { >>> + drm_printf(&p, "drm-cmdline-override:\t%s\n", >>> + file->override_cmdline); >>> + } >>> + mutex_unlock(&file->override_lock); >>> + >>> if (dev->driver->show_fdinfo) >>> dev->driver->show_fdinfo(&p, file); >>> } >>> diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h >>> index 1339e925af52..604d05fa6f0c 100644 >>> --- a/include/drm/drm_file.h >>> +++ b/include/drm/drm_file.h >>> @@ -370,6 +370,25 @@ struct drm_file { >>> */ >>> struct drm_prime_file_private prime; >>> >>> + /** >>> + * @comm: Overridden task comm >>> + * >>> + * Accessed under override_lock >>> + */ >>> + char *override_comm; >>> + >>> + /** >>> + * @cmdline: Overridden task cmdline >>> + * >>> + * Accessed under override_lock >>> + */ >>> + char *override_cmdline; >>> + >>> + /** >>> + * @override_lock: Serialize access to override_comm and override_cmdline >>> + */ >>> + struct mutex override_lock; >>> + >> >> I don't think this should go to drm just yet though. Only one driver can >> make use of it so I'd leave it for later and print from msm_show_fdinfo >> for now. > > This was my original approach but danvet asked that it be moved into > drm for consistency across drivers. (And really, I want the in-flight > amd and intel native-context stuff to motivate adding similar features > to amdgpu/i915/xe.)
IMO if implementation is not shared, not even by using helpers, I don't think data storage should be either, but it's not a deal breaker.
Regards,
Tvrtko
> > BR, > -R > >> Regards, >> >> Tvrtko >> >>> /* private: */ >>> #if IS_ENABLED(CONFIG_DRM_LEGACY) >>> unsigned long lock_count; /* DRI1 legacy lock count */
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