Acked-by: Jason Ekstrand <jason@xxxxxxxxxxxxxx> On Tue, Aug 10, 2021 at 7:34 AM Daniel Vetter <daniel.vetter@xxxxxxxx> wrote: > > We still have quite a bit more work to do with overall reworking of > the ttm-based dg1 code, but the uapi stuff is now finalized with the > latest pull. So remove that. > > This also fixes kerneldoc build warnings because we've included the > same headers in two places, resulting in sphinx complaining about > duplicated symbols. This regression has been created when we moved the > uapi definitions to the real include/uapi/ folder in 727ecd99a4c9 > ("drm/doc/rfc: drop the i915_gem_lmem.h header") > > Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> > Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> > Fixes: 727ecd99a4c9 ("drm/doc/rfc: drop the i915_gem_lmem.h header") > Cc: Matthew Auld <matthew.auld@xxxxxxxxx> > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx> > --- > Documentation/gpu/rfc/i915_gem_lmem.rst | 107 ------------------------ > 1 file changed, 107 deletions(-) > > diff --git a/Documentation/gpu/rfc/i915_gem_lmem.rst b/Documentation/gpu/rfc/i915_gem_lmem.rst > index 675ba8620d66..91be041e68cc 100644 > --- a/Documentation/gpu/rfc/i915_gem_lmem.rst > +++ b/Documentation/gpu/rfc/i915_gem_lmem.rst > @@ -22,110 +22,3 @@ real, with all the uAPI bits is: > * SET/GET ioctl caching(see `I915 SET/GET CACHING`_) > * Send RFC(with mesa-dev on cc) for final sign off on the uAPI > * Add pciid for DG1 and turn on uAPI for real > - > -New object placement and region query uAPI > -========================================== > -Starting from DG1 we need to give userspace the ability to allocate buffers from > -device local-memory. Currently the driver supports gem_create, which can place > -buffers in system memory via shmem, and the usual assortment of other > -interfaces, like dumb buffers and userptr. > - > -To support this new capability, while also providing a uAPI which will work > -beyond just DG1, we propose to offer three new bits of uAPI: > - > -DRM_I915_QUERY_MEMORY_REGIONS > ------------------------------ > -New query ID which allows userspace to discover the list of supported memory > -regions(like system-memory and local-memory) for a given device. We identify > -each region with a class and instance pair, which should be unique. The class > -here would be DEVICE or SYSTEM, and the instance would be zero, on platforms > -like DG1. > - > -Side note: The class/instance design is borrowed from our existing engine uAPI, > -where we describe every physical engine in terms of its class, and the > -particular instance, since we can have more than one per class. > - > -In the future we also want to expose more information which can further > -describe the capabilities of a region. > - > -.. kernel-doc:: include/uapi/drm/i915_drm.h > - :functions: drm_i915_gem_memory_class drm_i915_gem_memory_class_instance drm_i915_memory_region_info drm_i915_query_memory_regions > - > -GEM_CREATE_EXT > --------------- > -New ioctl which is basically just gem_create but now allows userspace to provide > -a chain of possible extensions. Note that if we don't provide any extensions and > -set flags=0 then we get the exact same behaviour as gem_create. > - > -Side note: We also need to support PXP[1] in the near future, which is also > -applicable to integrated platforms, and adds its own gem_create_ext extension, > -which basically lets userspace mark a buffer as "protected". > - > -.. kernel-doc:: include/uapi/drm/i915_drm.h > - :functions: drm_i915_gem_create_ext > - > -I915_GEM_CREATE_EXT_MEMORY_REGIONS > ----------------------------------- > -Implemented as an extension for gem_create_ext, we would now allow userspace to > -optionally provide an immutable list of preferred placements at creation time, > -in priority order, for a given buffer object. For the placements we expect > -them each to use the class/instance encoding, as per the output of the regions > -query. Having the list in priority order will be useful in the future when > -placing an object, say during eviction. > - > -.. kernel-doc:: include/uapi/drm/i915_drm.h > - :functions: drm_i915_gem_create_ext_memory_regions > - > -One fair criticism here is that this seems a little over-engineered[2]. If we > -just consider DG1 then yes, a simple gem_create.flags or something is totally > -all that's needed to tell the kernel to allocate the buffer in local-memory or > -whatever. However looking to the future we need uAPI which can also support > -upcoming Xe HP multi-tile architecture in a sane way, where there can be > -multiple local-memory instances for a given device, and so using both class and > -instance in our uAPI to describe regions is desirable, although specifically > -for DG1 it's uninteresting, since we only have a single local-memory instance. > - > -Existing uAPI issues > -==================== > -Some potential issues we still need to resolve. > - > -I915 MMAP > ---------- > -In i915 there are multiple ways to MMAP GEM object, including mapping the same > -object using different mapping types(WC vs WB), i.e multiple active mmaps per > -object. TTM expects one MMAP at most for the lifetime of the object. If it > -turns out that we have to backpedal here, there might be some potential > -userspace fallout. > - > -I915 SET/GET CACHING > --------------------- > -In i915 we have set/get_caching ioctl. TTM doesn't let us to change this, but > -DG1 doesn't support non-snooped pcie transactions, so we can just always > -allocate as WB for smem-only buffers. If/when our hw gains support for > -non-snooped pcie transactions then we must fix this mode at allocation time as > -a new GEM extension. > - > -This is related to the mmap problem, because in general (meaning, when we're > -not running on intel cpus) the cpu mmap must not, ever, be inconsistent with > -allocation mode. > - > -Possible idea is to let the kernel picks the mmap mode for userspace from the > -following table: > - > -smem-only: WB. Userspace does not need to call clflush. > - > -smem+lmem: We only ever allow a single mode, so simply allocate this as uncached > -memory, and always give userspace a WC mapping. GPU still does snooped access > -here(assuming we can't turn it off like on DG1), which is a bit inefficient. > - > -lmem only: always WC > - > -This means on discrete you only get a single mmap mode, all others must be > -rejected. That's probably going to be a new default mode or something like > -that. > - > -Links > -===== > -[1] https://patchwork.freedesktop.org/series/86798/ > - > -[2] https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5599#note_553791 > -- > 2.32.0 >