[Intel-gfx] [PATCH 27/32] drm/i915: Allow userspace to clone contexts on creation
Tvrtko Ursulin
tvrtko.ursulin at linux.intel.com
Wed Apr 17 09:50:59 UTC 2019
On 17/04/2019 08:56, Chris Wilson wrote:
> 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 at chris-wilson.co.uk>
> ---
> 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 d6bea51050c0..ba7582d955d1 100644
> --- a/drivers/gpu/drm/i915/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/i915_gem_context.c
> @@ -1682,8 +1682,214 @@ 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 = 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[] = {
> [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 7aef672ab3c7..7694113362d4 100644
> --- a/include/uapi/drm/i915_drm.h
> +++ b/include/uapi/drm/i915_drm.h
> @@ -1623,6 +1623,21 @@ 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;
>
Carry over for good measure:
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Regards,
Tvrtko
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