From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-14.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,HK_RANDOM_FROM,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4E22DC4320E for ; Mon, 26 Jul 2021 16:10:53 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 2157160240 for ; Mon, 26 Jul 2021 16:10:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 2157160240 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 73A0B72DCD; Mon, 26 Jul 2021 16:10:51 +0000 (UTC) Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by gabe.freedesktop.org (Postfix) with ESMTPS id 2C17E72DE3; Mon, 26 Jul 2021 16:10:50 +0000 (UTC) X-IronPort-AV: E=McAfee;i="6200,9189,10057"; a="273353081" X-IronPort-AV: E=Sophos;i="5.84,270,1620716400"; d="scan'208";a="273353081" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Jul 2021 09:10:47 -0700 X-IronPort-AV: E=Sophos;i="5.84,270,1620716400"; d="scan'208";a="436884138" Received: from jdonohue-mobl.ger.corp.intel.com (HELO [10.213.215.117]) ([10.213.215.117]) by fmsmga007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Jul 2021 09:10:45 -0700 Subject: Re: [PATCH] drm/i915/userptr: Probe existence of backing struct pages upon creation To: Jason Ekstrand , Maarten Lankhorst References: <20210723113405.427004-1-matthew.auld@intel.com> <0988bf67-c42a-1e7e-af77-ae2da65b036f@linux.intel.com> From: Tvrtko Ursulin Organization: Intel Corporation UK Plc Message-ID: Date: Mon, 26 Jul 2021 17:10:43 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: =?UTF-8?Q?Thomas_Hellstr=c3=b6m?= , Tvrtko Ursulin , Jordan Justen , Intel GFX , Maling list - DRI developers , Chris Wilson , Kenneth Graunke , Matthew Auld , Daniel Vetter Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On 26/07/2021 16:14, Jason Ekstrand wrote: > On Mon, Jul 26, 2021 at 3:31 AM Maarten Lankhorst > wrote: >> >> Op 23-07-2021 om 13:34 schreef Matthew Auld: >>> From: Chris Wilson >>> >>> 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 >>> --- >>> 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 24e18219eb50..bbb7cac43eb4 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 975087553ea0..0d290535a6e5 100644 >>> --- a/include/uapi/drm/i915_drm.h >>> +++ b/include/uapi/drm/i915_drm.h >>> @@ -674,6 +674,9 @@ 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 { >>> @@ -2222,12 +2225,29 @@ 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. >> >> Could we use _VALIDATE instead of probe? Or at least pin the pages as well, so we don't have to do it later? > > I only care that the name matches what it does. _VALIDATE sounds like > it does a full validation of everything such that, if the import > succeeds, execbuf will as well. If we pin the pages at the same time, > maybe that's true? _PROBE, on the other hand, sounds a lot more like No it is not possible to guarantee backing store remains valid until execbuf. > a one-time best-effort check which may race with other stuff and > doesn't guarantee future success. That's in line with what the > current patch does. > >> We already have i915_gem_object_userptr_validate, no need to dupe it. > > I have no opinion on this. I was actually suggesting the same as Maarten here - that we should add a "populate" flag. But opinion was that was not desired - please look for the older threads to see the reasoning there. Regards, Tvrtko