Commit b81dde71 authored by Chris Wilson's avatar Chris Wilson

drm/i915: Allow userspace to clone contexts on creation

A usecase arose out of handling context recovery in mesa, whereby they
wish to recreate a context with fresh logical state but preserving all
other details of the original. Currently, they create a new context and
iterate over which bits they want to copy across, but it would much more
convenient if they were able to just pass in a target context to clone
during creation. This essentially extends the setparam during creation
to pull the details from a target context instead of the user supplied
parameters.

The ideal here is that we don't expose control over anything more than
can be obtained via CONTEXT_PARAM. That is userspace retains explicit
control over all features, and this api is just convenience.

For example, you could replace

	struct context_param p = { .param = CONTEXT_PARAM_VM };

	param.ctx_id = old_id;
	gem_context_get_param(&p.param);

	new_id = gem_context_create();

	param.ctx_id = new_id;
	gem_context_set_param(&p.param);

	gem_vm_destroy(param.value); /* drop the ref to VM_ID handle */

with

	struct create_ext_param p = {
	  { .name = CONTEXT_CREATE_CLONE },
	  .clone_id = old_id,
	  .flags = CLONE_FLAGS_VM
	}
	new_id = gem_context_create_ext(&p);

and not have to worry about stray namespace pollution etc.
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190521211134.16117-5-chris@chris-wilson.co.uk
parent 8319f44c
...@@ -1723,8 +1723,214 @@ static int create_setparam(struct i915_user_extension __user *ext, void *data) ...@@ -1723,8 +1723,214 @@ static int create_setparam(struct i915_user_extension __user *ext, void *data)
return ctx_setparam(arg->fpriv, arg->ctx, &local.param); return ctx_setparam(arg->fpriv, arg->ctx, &local.param);
} }
static int clone_engines(struct i915_gem_context *dst,
struct i915_gem_context *src)
{
struct i915_gem_engines *e = i915_gem_context_lock_engines(src);
struct i915_gem_engines *clone;
bool user_engines;
unsigned long n;
clone = kmalloc(struct_size(e, engines, e->num_engines), GFP_KERNEL);
if (!clone)
goto err_unlock;
clone->i915 = dst->i915;
for (n = 0; n < e->num_engines; n++) {
if (!e->engines[n]) {
clone->engines[n] = NULL;
continue;
}
clone->engines[n] =
intel_context_create(dst, e->engines[n]->engine);
if (!clone->engines[n]) {
__free_engines(clone, n);
goto err_unlock;
}
}
clone->num_engines = n;
user_engines = i915_gem_context_user_engines(src);
i915_gem_context_unlock_engines(src);
free_engines(dst->engines);
RCU_INIT_POINTER(dst->engines, clone);
if (user_engines)
i915_gem_context_set_user_engines(dst);
else
i915_gem_context_clear_user_engines(dst);
return 0;
err_unlock:
i915_gem_context_unlock_engines(src);
return -ENOMEM;
}
static int clone_flags(struct i915_gem_context *dst,
struct i915_gem_context *src)
{
dst->user_flags = src->user_flags;
return 0;
}
static int clone_schedattr(struct i915_gem_context *dst,
struct i915_gem_context *src)
{
dst->sched = src->sched;
return 0;
}
static int clone_sseu(struct i915_gem_context *dst,
struct i915_gem_context *src)
{
struct i915_gem_engines *e = i915_gem_context_lock_engines(src);
struct i915_gem_engines *clone;
unsigned long n;
int err;
clone = dst->engines; /* no locking required; sole access */
if (e->num_engines != clone->num_engines) {
err = -EINVAL;
goto unlock;
}
for (n = 0; n < e->num_engines; n++) {
struct intel_context *ce = e->engines[n];
if (clone->engines[n]->engine->class != ce->engine->class) {
/* Must have compatible engine maps! */
err = -EINVAL;
goto unlock;
}
/* serialises with set_sseu */
err = intel_context_lock_pinned(ce);
if (err)
goto unlock;
clone->engines[n]->sseu = ce->sseu;
intel_context_unlock_pinned(ce);
}
err = 0;
unlock:
i915_gem_context_unlock_engines(src);
return err;
}
static int clone_timeline(struct i915_gem_context *dst,
struct i915_gem_context *src)
{
if (src->timeline) {
GEM_BUG_ON(src->timeline == dst->timeline);
if (dst->timeline)
i915_timeline_put(dst->timeline);
dst->timeline = i915_timeline_get(src->timeline);
}
return 0;
}
static int clone_vm(struct i915_gem_context *dst,
struct i915_gem_context *src)
{
struct i915_hw_ppgtt *ppgtt;
rcu_read_lock();
do {
ppgtt = READ_ONCE(src->ppgtt);
if (!ppgtt)
break;
if (!kref_get_unless_zero(&ppgtt->ref))
continue;
/*
* This ppgtt may have be reallocated between
* the read and the kref, and reassigned to a third
* context. In order to avoid inadvertent sharing
* of this ppgtt with that third context (and not
* src), we have to confirm that we have the same
* ppgtt after passing through the strong memory
* barrier implied by a successful
* kref_get_unless_zero().
*
* Once we have acquired the current ppgtt of src,
* we no longer care if it is released from src, as
* it cannot be reallocated elsewhere.
*/
if (ppgtt == READ_ONCE(src->ppgtt))
break;
i915_ppgtt_put(ppgtt);
} while (1);
rcu_read_unlock();
if (ppgtt) {
__assign_ppgtt(dst, ppgtt);
i915_ppgtt_put(ppgtt);
}
return 0;
}
static int create_clone(struct i915_user_extension __user *ext, void *data)
{
static int (* const fn[])(struct i915_gem_context *dst,
struct i915_gem_context *src) = {
#define MAP(x, y) [ilog2(I915_CONTEXT_CLONE_##x)] = y
MAP(ENGINES, clone_engines),
MAP(FLAGS, clone_flags),
MAP(SCHEDATTR, clone_schedattr),
MAP(SSEU, clone_sseu),
MAP(TIMELINE, clone_timeline),
MAP(VM, clone_vm),
#undef MAP
};
struct drm_i915_gem_context_create_ext_clone local;
const struct create_ext *arg = data;
struct i915_gem_context *dst = arg->ctx;
struct i915_gem_context *src;
int err, bit;
if (copy_from_user(&local, ext, sizeof(local)))
return -EFAULT;
BUILD_BUG_ON(GENMASK(BITS_PER_TYPE(local.flags) - 1, ARRAY_SIZE(fn)) !=
I915_CONTEXT_CLONE_UNKNOWN);
if (local.flags & I915_CONTEXT_CLONE_UNKNOWN)
return -EINVAL;
if (local.rsvd)
return -EINVAL;
rcu_read_lock();
src = __i915_gem_context_lookup_rcu(arg->fpriv, local.clone_id);
rcu_read_unlock();
if (!src)
return -ENOENT;
GEM_BUG_ON(src == dst);
for (bit = 0; bit < ARRAY_SIZE(fn); bit++) {
if (!(local.flags & BIT(bit)))
continue;
err = fn[bit](dst, src);
if (err)
return err;
}
return 0;
}
static const i915_user_extension_fn create_extensions[] = { static const i915_user_extension_fn create_extensions[] = {
[I915_CONTEXT_CREATE_EXT_SETPARAM] = create_setparam, [I915_CONTEXT_CREATE_EXT_SETPARAM] = create_setparam,
[I915_CONTEXT_CREATE_EXT_CLONE] = create_clone,
}; };
static bool client_is_banned(struct drm_i915_file_private *file_priv) static bool client_is_banned(struct drm_i915_file_private *file_priv)
......
...@@ -1624,6 +1624,21 @@ struct drm_i915_gem_context_create_ext_setparam { ...@@ -1624,6 +1624,21 @@ struct drm_i915_gem_context_create_ext_setparam {
struct drm_i915_gem_context_param param; struct drm_i915_gem_context_param param;
}; };
struct drm_i915_gem_context_create_ext_clone {
#define I915_CONTEXT_CREATE_EXT_CLONE 1
struct i915_user_extension base;
__u32 clone_id;
__u32 flags;
#define I915_CONTEXT_CLONE_ENGINES (1u << 0)
#define I915_CONTEXT_CLONE_FLAGS (1u << 1)
#define I915_CONTEXT_CLONE_SCHEDATTR (1u << 2)
#define I915_CONTEXT_CLONE_SSEU (1u << 3)
#define I915_CONTEXT_CLONE_TIMELINE (1u << 4)
#define I915_CONTEXT_CLONE_VM (1u << 5)
#define I915_CONTEXT_CLONE_UNKNOWN -(I915_CONTEXT_CLONE_VM << 1)
__u64 rsvd;
};
struct drm_i915_gem_context_destroy { struct drm_i915_gem_context_destroy {
__u32 ctx_id; __u32 ctx_id;
__u32 pad; __u32 pad;
......
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