From b65a9489730a2494f7a2a33a6eb0a12b8f1dd193 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Fri, 23 Jul 2021 12:34:05 +0100 Subject: [PATCH] drm/i915/userptr: Probe existence of backing struct pages upon creation MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Jason Ekstrand requested a more efficient method than userptr+set-domain to determine if the userptr object was backed by a complete set of pages upon creation. To be more efficient than simply populating the userptr using get_user_pages() (as done by the call to set-domain or execbuf), we can walk the tree of vm_area_struct and check for gaps or vma not backed by struct page (VM_PFNMAP). The question is how to handle VM_MIXEDMAP which may be either struct page or pfn backed... With discrete we are going to drop support for set_domain(), so offering a way to probe the pages, without having to resort to dummy batches has been requested. v2: - add new query param for the PROBE flag, so userspace can easily check if the kernel supports it(Jason). - use mmap_read_{lock, unlock}. - add some kernel-doc. v3: - In the docs also mention that PROBE doesn't guarantee that the pages will remain valid by the time they are actually used(Tvrtko). - Add a small comment for the hole finding logic(Jason). - Move the param next to all the other params which just return true. Testcase: igt/gem_userptr_blits/probe Signed-off-by: Chris Wilson Signed-off-by: Matthew Auld Cc: Thomas Hellström Cc: Maarten Lankhorst Cc: Tvrtko Ursulin Cc: Jordan Justen Cc: Kenneth Graunke Cc: Jason Ekstrand Cc: Daniel Vetter Cc: Ramalingam C Reviewed-by: Tvrtko Ursulin Acked-by: Kenneth Graunke Reviewed-by: Jason Ekstrand Acked-by: Maarten Lankhorst Signed-off-by: Maarten Lankhorst Link: https://patchwork.freedesktop.org/patch/msgid/20210723113405.427004-1-matthew.auld@intel.com --- drivers/gpu/drm/i915/gem/i915_gem_userptr.c | 41 ++++++++++++++++++++- drivers/gpu/drm/i915/i915_getparam.c | 1 + include/uapi/drm/i915_drm.h | 20 ++++++++++ 3 files changed, 61 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c index 56edfeff8c02..468a7a617fbf 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c @@ -422,6 +422,34 @@ static const struct drm_i915_gem_object_ops i915_gem_userptr_ops = { #endif +static int +probe_range(struct mm_struct *mm, unsigned long addr, unsigned long len) +{ + const unsigned long end = addr + len; + struct vm_area_struct *vma; + int ret = -EFAULT; + + mmap_read_lock(mm); + for (vma = find_vma(mm, addr); vma; vma = vma->vm_next) { + /* Check for holes, note that we also update the addr below */ + if (vma->vm_start > addr) + break; + + if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP)) + break; + + if (vma->vm_end >= end) { + ret = 0; + break; + } + + addr = vma->vm_end; + } + mmap_read_unlock(mm); + + return ret; +} + /* * Creates a new mm object that wraps some normal memory from the process * context - user memory. @@ -477,7 +505,8 @@ i915_gem_userptr_ioctl(struct drm_device *dev, } if (args->flags & ~(I915_USERPTR_READ_ONLY | - I915_USERPTR_UNSYNCHRONIZED)) + I915_USERPTR_UNSYNCHRONIZED | + I915_USERPTR_PROBE)) return -EINVAL; if (i915_gem_object_size_2big(args->user_size)) @@ -504,6 +533,16 @@ i915_gem_userptr_ioctl(struct drm_device *dev, return -ENODEV; } + if (args->flags & I915_USERPTR_PROBE) { + /* + * Check that the range pointed to represents real struct + * pages and not iomappings (at this moment in time!) + */ + ret = probe_range(current->mm, args->user_ptr, args->user_size); + if (ret) + return ret; + } + #ifdef CONFIG_MMU_NOTIFIER obj = i915_gem_object_alloc(); if (obj == NULL) diff --git a/drivers/gpu/drm/i915/i915_getparam.c b/drivers/gpu/drm/i915/i915_getparam.c index e289397d9178..77490cb5ff9c 100644 --- a/drivers/gpu/drm/i915/i915_getparam.c +++ b/drivers/gpu/drm/i915/i915_getparam.c @@ -134,6 +134,7 @@ int i915_getparam_ioctl(struct drm_device *dev, void *data, case I915_PARAM_HAS_EXEC_FENCE_ARRAY: case I915_PARAM_HAS_EXEC_SUBMIT_FENCE: case I915_PARAM_HAS_EXEC_TIMELINE_FENCES: + case I915_PARAM_HAS_USERPTR_PROBE: /* For the time being all of these are always true; * if some supported hardware does not have one of these * features this value needs to be provided from diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h index 7f13d241417f..bde5860b3686 100644 --- a/include/uapi/drm/i915_drm.h +++ b/include/uapi/drm/i915_drm.h @@ -683,6 +683,9 @@ typedef struct drm_i915_irq_wait { */ #define I915_PARAM_HAS_EXEC_TIMELINE_FENCES 55 +/* Query if the kernel supports the I915_USERPTR_PROBE flag. */ +#define I915_PARAM_HAS_USERPTR_PROBE 56 + /* Must be kept compact -- no holes and well documented */ typedef struct drm_i915_getparam { @@ -2231,12 +2234,29 @@ struct drm_i915_gem_userptr { * through the GTT. If the HW can't support readonly access, an error is * returned. * + * I915_USERPTR_PROBE: + * + * Probe the provided @user_ptr range and validate that the @user_ptr is + * indeed pointing to normal memory and that the range is also valid. + * For example if some garbage address is given to the kernel, then this + * should complain. + * + * Returns -EFAULT if the probe failed. + * + * Note that this doesn't populate the backing pages, and also doesn't + * guarantee that the object will remain valid when the object is + * eventually used. + * + * The kernel supports this feature if I915_PARAM_HAS_USERPTR_PROBE + * returns a non-zero value. + * * I915_USERPTR_UNSYNCHRONIZED: * * NOT USED. Setting this flag will result in an error. */ __u32 flags; #define I915_USERPTR_READ_ONLY 0x1 +#define I915_USERPTR_PROBE 0x2 #define I915_USERPTR_UNSYNCHRONIZED 0x80000000 /** * @handle: Returned handle for the object.