drm/vmwgfx: Kill unneeded legacy security features

At one point, the GPU command verifier and user-space handle manager
couldn't properly protect GPU clients from accessing each other's data.
Instead there was an elaborate mechanism to make sure only the active
master's primary clients could render. The other clients were either
put to sleep or even killed (if the master had exited). VRAM was
evicted on master switch. With the advent of render-node functionality,
we relaxed the VRAM eviction, but the other mechanisms stayed in place.

Now that the GPU command verifier and ttm object manager properly
isolate primary clients from different master realms we can remove the
master switch related code and drop those legacy features.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Deepak Rawat <drawat@vmware.com>
Acked-by: Emil Velikov <emil.velikov@collabora.com>

drivers/gpu/drm/vmwgfx/ttm_lock.c

@@ -29,7 +29,6 @@
  * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
  */
 
-#include <drm/ttm/ttm_module.h>
 #include <linux/atomic.h>
 #include <linux/errno.h>
 #include <linux/wait.h>
@@ -49,8 +48,6 @@ void ttm_lock_init(struct ttm_lock *lock)
 	init_waitqueue_head(&lock->queue);
 	lock->rw = 0;
 	lock->flags = 0;
-	lock->kill_takers = false;
-	lock->signal = SIGKILL;
 }
 
 void ttm_read_unlock(struct ttm_lock *lock)
@@ -66,11 +63,6 @@ static bool __ttm_read_lock(struct ttm_lock *lock)
 	bool locked = false;
 
 	spin_lock(&lock->lock);
-	if (unlikely(lock->kill_takers)) {
-		send_sig(lock->signal, current, 0);
-		spin_unlock(&lock->lock);
-		return false;
-	}
 	if (lock->rw >= 0 && lock->flags == 0) {
 		++lock->rw;
 		locked = true;
@@ -98,11 +90,6 @@ static bool __ttm_read_trylock(struct ttm_lock *lock, bool *locked)
 	*locked = false;
 
 	spin_lock(&lock->lock);
-	if (unlikely(lock->kill_takers)) {
-		send_sig(lock->signal, current, 0);
-		spin_unlock(&lock->lock);
-		return false;
-	}
 	if (lock->rw >= 0 && lock->flags == 0) {
 		++lock->rw;
 		block = false;
@@ -147,11 +134,6 @@ static bool __ttm_write_lock(struct ttm_lock *lock)
 	bool locked = false;
 
 	spin_lock(&lock->lock);
-	if (unlikely(lock->kill_takers)) {
-		send_sig(lock->signal, current, 0);
-		spin_unlock(&lock->lock);
-		return false;
-	}
 	if (lock->rw == 0 && ((lock->flags & ~TTM_WRITE_LOCK_PENDING) == 0)) {
 		lock->rw = -1;
 		lock->flags &= ~TTM_WRITE_LOCK_PENDING;
@@ -182,88 +164,6 @@ int ttm_write_lock(struct ttm_lock *lock, bool interruptible)
 	return ret;
 }
 
-static int __ttm_vt_unlock(struct ttm_lock *lock)
-{
-	int ret = 0;
-
-	spin_lock(&lock->lock);
-	if (unlikely(!(lock->flags & TTM_VT_LOCK)))
-		ret = -EINVAL;
-	lock->flags &= ~TTM_VT_LOCK;
-	wake_up_all(&lock->queue);
-	spin_unlock(&lock->lock);
-
-	return ret;
-}
-
-static void ttm_vt_lock_remove(struct ttm_base_object **p_base)
-{
-	struct ttm_base_object *base = *p_base;
-	struct ttm_lock *lock = container_of(base, struct ttm_lock, base);
-	int ret;
-
-	*p_base = NULL;
-	ret = __ttm_vt_unlock(lock);
-	BUG_ON(ret != 0);
-}
-
-static bool __ttm_vt_lock(struct ttm_lock *lock)
-{
-	bool locked = false;
-
-	spin_lock(&lock->lock);
-	if (lock->rw == 0) {
-		lock->flags &= ~TTM_VT_LOCK_PENDING;
-		lock->flags |= TTM_VT_LOCK;
-		locked = true;
-	} else {
-		lock->flags |= TTM_VT_LOCK_PENDING;
-	}
-	spin_unlock(&lock->lock);
-	return locked;
-}
-
-int ttm_vt_lock(struct ttm_lock *lock,
-		bool interruptible,
-		struct ttm_object_file *tfile)
-{
-	int ret = 0;
-
-	if (interruptible) {
-		ret = wait_event_interruptible(lock->queue,
-					       __ttm_vt_lock(lock));
-		if (unlikely(ret != 0)) {
-			spin_lock(&lock->lock);
-			lock->flags &= ~TTM_VT_LOCK_PENDING;
-			wake_up_all(&lock->queue);
-			spin_unlock(&lock->lock);
-			return ret;
-		}
-	} else
-		wait_event(lock->queue, __ttm_vt_lock(lock));
-
-	/*
-	 * Add a base-object, the destructor of which will
-	 * make sure the lock is released if the client dies
-	 * while holding it.
-	 */
-
-	ret = ttm_base_object_init(tfile, &lock->base, false,
-				   ttm_lock_type, &ttm_vt_lock_remove, NULL);
-	if (ret)
-		(void)__ttm_vt_unlock(lock);
-	else
-		lock->vt_holder = tfile;
-
-	return ret;
-}
-
-int ttm_vt_unlock(struct ttm_lock *lock)
-{
-	return ttm_ref_object_base_unref(lock->vt_holder,
-					 lock->base.handle, TTM_REF_USAGE);
-}
-
 void ttm_suspend_unlock(struct ttm_lock *lock)
 {
 	spin_lock(&lock->lock);

drivers/gpu/drm/vmwgfx/ttm_lock.h

@@ -63,8 +63,6 @@
  * @lock: Spinlock protecting some lock members.
  * @rw: Read-write lock counter. Protected by @lock.
  * @flags: Lock state. Protected by @lock.
- * @kill_takers: Boolean whether to kill takers of the lock.
- * @signal: Signal to send when kill_takers is true.
  */
 
 struct ttm_lock {
@@ -73,9 +71,6 @@ struct ttm_lock {
 	spinlock_t lock;
 	int32_t rw;
 	uint32_t flags;
-	bool kill_takers;
-	int signal;
-	struct ttm_object_file *vt_holder;
 };
 
 
@@ -220,29 +215,4 @@ extern void ttm_write_unlock(struct ttm_lock *lock);
  */
 extern int ttm_write_lock(struct ttm_lock *lock, bool interruptible);
 
-/**
- * ttm_lock_set_kill
- *
- * @lock: Pointer to a struct ttm_lock
- * @val: Boolean whether to kill processes taking the lock.
- * @signal: Signal to send to the process taking the lock.
- *
- * The kill-when-taking-lock functionality is used to kill processes that keep
- * on using the TTM functionality when its resources has been taken down, for
- * example when the X server exits. A typical sequence would look like this:
- * - X server takes lock in write mode.
- * - ttm_lock_set_kill() is called with @val set to true.
- * - As part of X server exit, TTM resources are taken down.
- * - X server releases the lock on file release.
- * - Another dri client wants to render, takes the lock and is killed.
- *
- */
-static inline void ttm_lock_set_kill(struct ttm_lock *lock, bool val,
-				     int signal)
-{
-	lock->kill_takers = val;
-	if (val)
-		lock->signal = signal;
-}
-
 #endif