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: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem_context.c | 206 ++++++++++++++++++++++++
include/uapi/drm/i915_drm.h | 15 ++
2 files changed, 221 insertions(+)
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 9286a31ef2ed..5c8fed7717f6 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -1699,8 +1699,214 @@ static int create_setparam(struct i915_user_extension __user *ext, void *data)
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, *clone;
+ bool user_engines;
+ unsigned long n;
+
+ e = i915_gem_context_engine_list_lock(src);
+
+ 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_n(clone, n);
+ goto err_unlock;
+ }
+ }
+ clone->num_engines = n;
+
+ user_engines = i915_gem_context_user_engines(src);
+ i915_gem_context_engine_list_unlock(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_engine_list_unlock(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, *clone;
+ unsigned long n;
+ int err;
+
+ clone = dst->engines; /* no locking required; sole access */
+ e = i915_gem_context_engine_list_lock(src);
+ 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;
+ }
+
+ err = intel_context_pin_lock(ce); /* serialises with set_sseu */
+ if (err)
+ goto unlock;
+
+ clone->engines[n]->sseu = ce->sseu;
+ intel_context_pin_unlock(ce);
+ }
+
+ err = 0;
+unlock:
+ i915_gem_context_engine_list_unlock(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[] = {
[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)
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index a0064d7e87c2..ab30bcd7c1f1 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -1619,6 +1619,21 @@ struct drm_i915_gem_context_create_ext_setparam {
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 {
__u32 ctx_id;
__u32 pad;
--
2.20.1
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