<div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">On Fri, Dec 15, 2017 at 5:42 AM, Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk" target="_blank">chris@chris-wilson.co.uk</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Every client (everyone instance that opens /dev/dri/card0 or the render nodes), receives a unique per-process GTT (where supported by the hardware, unfortunately that means only Broadwell and later). Every context created by each client, in turns receives its own unique ppGTT. This is overkill in terms of allocations and tracking, both in the kernel and in the hardware, as we could be sharing the per-client GTT amongst all of its contexts. The downside is that context segregation is reduced, a stray write from one context may affect another, and so we must honour any client requests that require robust segregation (e.g. ARB_robustness). Signed-off-by: Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a>> --- src/mesa/drivers/dri/i965/brw_bufmgr.c | 23 +++++++++++++++++------ src/mesa/drivers/dri/i965/brw_bufmgr.h | 2 +- src/mesa/drivers/dri/i965/brw_context.c | 2 +- 3 files changed, 19 insertions(+), 8 deletions(-) diff --git a/src/mesa/drivers/dri/i965/brw_bufmgr.c b/src/mesa/drivers/dri/i965/brw_bufmgr.c index 52b5bf97a1..d8a9635f5d 100644 --- a/src/mesa/drivers/dri/i965/brw_bufmgr.c +++ b/src/mesa/drivers/dri/i965/brw_bufmgr.c @@ -1297,13 +1297,24 @@ init_cache_buckets(struct brw_bufmgr *bufmgr) } uint32_t -brw_create_hw_context(struct brw_bufmgr *bufmgr) +brw_create_hw_context(struct brw_bufmgr *bufmgr, unsigned int flags) { - struct drm_i915_gem_context_create create = { }; - int ret = drmIoctl(bufmgr->fd, DRM_IOCTL_I915_GEM_CONTEXT_CREATE, &create); - if (ret != 0) { - DBG("DRM_IOCTL_I915_GEM_CONTEXT_CREATE failed: %s\n", strerror(errno)); - return 0; + struct local_i915_gem_context_create_v2 { + uint32_t ctx_id; /* out */ + uint32_t flags; +#define I915_GEM_CONTEXT_SHARE_GTT 0x1 + uint32_t share_ctx; </blockquote><div> </div><div>So, we've left share_ctx as 0. What does that mean? Does that mean that we share with some context that was implicitly created by opening /dev/dri/card0? Does it mean we share with the default context and therefore other processes? If some other component (say, vaapi) opens /dev/dri/card0 but from the same process, are we now sharing with it?</div><div> </div><div>I mean, as far as the kernel UABI bits go, it seems perfectly reasonable. There are just a lot of crazy implications here and I'd like to understand the subtle details better. </div><div> </div><div>--Jason </div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> + uint32_t pad; + } create = { }; +#define LOCAL_IOCTL_I915_GEM_CONTEXT_CREATE DRM_IOWR (DRM_COMMAND_BASE + DRM_I915_GEM_CONTEXT_CREATE, struct local_i915_gem_context_create_v2) + + if (!(flags & __DRI_CTX_FLAG_ROBUST_BUFFER_ACCESS)) + create.flags |= I915_GEM_CONTEXT_SHARE_GTT; + + if (drmIoctl(bufmgr->fd, LOCAL_IOCTL_I915_GEM_CONTEXT_CREATE, &create)) { + create.flags = 0; + if (drmIoctl(bufmgr->fd, LOCAL_IOCTL_I915_GEM_CONTEXT_CREATE, &create)) + return 0; } return create.ctx_id; diff --git a/src/mesa/drivers/dri/i965/brw_bufmgr.h b/src/mesa/drivers/dri/i965/brw_bufmgr.h index 0ae541cda0..f5191aff76 100644 --- a/src/mesa/drivers/dri/i965/brw_bufmgr.h +++ b/src/mesa/drivers/dri/i965/brw_bufmgr.h @@ -321,7 +321,7 @@ void brw_bufmgr_enable_reuse(struct brw_bufmgr *bufmgr); int brw_bo_wait(struct brw_bo *bo, int64_t timeout_ns); -uint32_t brw_create_hw_context(struct brw_bufmgr *bufmgr); +uint32_t brw_create_hw_context(struct brw_bufmgr *bufmgr, unsigned int flags); #define BRW_CONTEXT_LOW_PRIORITY ((I915_CONTEXT_MIN_USER_PRIORITY-1)/2) #define BRW_CONTEXT_MEDIUM_PRIORITY (I915_CONTEXT_DEFAULT_PRIORITY) diff --git a/src/mesa/drivers/dri/i965/brw_context.c b/src/mesa/drivers/dri/i965/brw_context.c index 9e0f875b27..e374236b6b 100644 --- a/src/mesa/drivers/dri/i965/brw_context.c +++ b/src/mesa/drivers/dri/i965/brw_context.c @@ -986,7 +986,7 @@ brwCreateContext(gl_api api, * This is required for transform feedback buffer offsets, query objects, * and also allows us to reduce how much state we have to emit. */ - brw->hw_ctx = brw_create_hw_context(brw->bufmgr); + brw->hw_ctx = brw_create_hw_context(brw->bufmgr, ctx_config->flags); if (!brw->hw_ctx && devinfo->gen >= 6) { fprintf(stderr, "Failed to create hardware context.\n"); intelDestroyContext(driContextPriv); -- 2.15.1 _______________________________________________ mesa-dev mailing list <a href="mailto:mesa-dev@lists.freedesktop.org">mesa-dev@lists.freedesktop.org</a> <a href="https://lists.freedesktop.org/mailman/listinfo/mesa-dev" rel="noreferrer" target="_blank">https://lists.freedesktop.org/mailman/listinfo/mesa-dev</a> </blockquote></div> </div></div>