linux-kernel - [PATCH v7 3/3] drm: Expand max DRM device number to full MINORBITS

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20240823163048.2676257-4-michal.winiarski@intel.com>
Date: Fri, 23 Aug 2024 18:30:48 +0200
From: Michał Winiarski <michal.winiarski@...el.com>
To: <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
	<intel-gfx@...ts.freedesktop.org>, <intel-xe@...ts.freedesktop.org>
CC: David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, Maarten
 Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard
	<mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, Simon Ser
	<contact@...rsion.fr>, Matthew Wilcox <willy@...radead.org>, Oded Gabbay
	<ogabbay@...nel.org>, Christian König
	<christian.koenig@....com>, James Zhu <James.Zhu@....com>, Pekka Paalanen
	<pekka.paalanen@...labora.com>, Emil Velikov <emil.l.velikov@...il.com>, Alex
 Deucher <alexdeucher@...il.com>, Michał Winiarski
	<michal.winiarski@...el.com>
Subject: [PATCH v7 3/3] drm: Expand max DRM device number to full MINORBITS

Having a limit of 64 DRM devices is not good enough for modern world
where we have multi-GPU servers, SR-IOV virtual functions and virtual
devices used for testing.
Let's utilize full minor range for DRM devices.
To avoid regressing the existing userspace, we're still maintaining the
numbering scheme where 0-63 is used for primary, 64-127 is reserved
(formerly for control) and 128-191 is used for render.
For minors >= 192, we're allocating minors dynamically on a first-come,
first-served basis.

Acked-by: James Zhu <James.Zhu@....com>
Signed-off-by: Michał Winiarski <michal.winiarski@...el.com>
---
 drivers/gpu/drm/drm_drv.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 7e0fa5a2a3182..c734e6a1c4ce2 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -121,10 +121,19 @@ static void drm_minor_alloc_release(struct drm_device *dev, void *data)
 	xa_erase(drm_minor_get_xa(minor->type), minor->index);
 }
 
+/*
+ * DRM used to support 64 devices, for backwards compatibility we need to maintain the
+ * minor allocation scheme where minors 0-63 are primary nodes, 64-127 are control nodes,
+ * and 128-191 are render nodes.
+ * After reaching the limit, we're allocating minors dynamically - first-come, first-serve.
+ * Accel nodes are using a distinct major, so the minors are allocated in continuous 0-MAX
+ * range.
+ */
 #define DRM_MINOR_LIMIT(t) ({ \
 	typeof(t) _t = (t); \
 	_t == DRM_MINOR_ACCEL ? XA_LIMIT(0, ACCEL_MAX_MINORS) : XA_LIMIT(64 * _t, 64 * _t + 63); \
 })
+#define DRM_EXTENDED_MINOR_LIMIT XA_LIMIT(192, (1 << MINORBITS) - 1)
 
 static int drm_minor_alloc(struct drm_device *dev, enum drm_minor_type type)
 {
@@ -140,6 +149,9 @@ static int drm_minor_alloc(struct drm_device *dev, enum drm_minor_type type)
 
 	r = xa_alloc(drm_minor_get_xa(type), &minor->index,
 		     NULL, DRM_MINOR_LIMIT(type), GFP_KERNEL);
+	if (r == -EBUSY && (type == DRM_MINOR_PRIMARY || type == DRM_MINOR_RENDER))
+		r = xa_alloc(&drm_minors_xa, &minor->index,
+			     NULL, DRM_EXTENDED_MINOR_LIMIT, GFP_KERNEL);
 	if (r < 0)
 		return r;
 
-- 
2.46.0