linux-kernel - [PATCH v2 8/9] drm/fdinfo: Add comm/cmdline override fields

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Date:   Thu, 27 Apr 2023 10:53:32 -0700
From:   Rob Clark <robdclark@...il.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     freedreno@...ts.freedesktop.org, Daniel Vetter <daniel@...ll.ch>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Christopher Healy <healych@...zon.com>,
        Emil Velikov <emil.l.velikov@...il.com>,
        Christian König <christian.koenig@....com>,
        Rob Clark <robdclark@...omium.org>,
        David Airlie <airlied@...il.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Jonathan Corbet <corbet@....net>,
        linux-doc@...r.kernel.org (open list:DOCUMENTATION),
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v2 8/9] drm/fdinfo: Add comm/cmdline override fields

From: Rob Clark <robdclark@...omium.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@...omium.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.
+
 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);
+	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;
+
 	/* private: */
 #if IS_ENABLED(CONFIG_DRM_LEGACY)
 	unsigned long lock_count; /* DRI1 legacy lock count */
-- 
2.39.2