From patchwork Thu Oct 20 11:03:08 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Christoph Hellwig X-Patchwork-Id: 13013214 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 82B0EC4332F for ; Thu, 20 Oct 2022 11:03:34 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 0422B10E5AC; Thu, 20 Oct 2022 11:03:33 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) by gabe.freedesktop.org (Postfix) with ESMTPS id 4155110E5AC; Thu, 20 Oct 2022 11:03:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Content-Transfer-Encoding: Content-Type:MIME-Version:Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To: Content-ID:Content-Description:In-Reply-To:References; bh=vzIIWL4qI+c7mLkQ6mO5LnCAvr9Io4h5i2791g9WkoA=; b=MZ/G2NjTrIeSSb0P5Eq4IPEecE ZMFKfZxJ1PDCqEAe6f2+qLVPQ5N/Me2uQxi2vNqoiCQ62z4iYcvq7o3MUZQG1gaGuoalGlU7FYpw+ QqiiJUBOTP/BWNWS2WhP3VgjHQp9LpfiJkCYpxTiot+DcrKM59G4dyRsXw6WddgD7prW9xx+5lzEK YhyPAAHlk7eh36u+IJ/cz/k0FUtYT3iaZcvorkz7d0Y0gv3l58Y8GYGnd+NJbTqV7S6aSRczV1dDn cnwGMJXZla76IO4bR/Idi9So0lOh6wp/EQojVmOHSjmI3jQ1MWMcd0Sw0EtvYakpUN8VC63ija8Q2 TjlBIdBw==; Received: from [88.128.92.117] (helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1olTKU-00DsxZ-8E; Thu, 20 Oct 2022 11:03:14 +0000 From: Christoph Hellwig To: jani.nikula@linux.intel.com, joonas.lahtinen@linux.intel.com, rodrigo.vivi@intel.com, tvrtko.ursulin@linux.intel.com Date: Thu, 20 Oct 2022 13:03:08 +0200 Message-Id: <20221020110308.1582518-1-hch@lst.de> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Subject: [Intel-gfx] [PATCH] drm/i915: stop abusing swiotlb_max_segment X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: intel-gfx@lists.freedesktop.org, marmarek@invisiblethingslab.com, dri-devel@lists.freedesktop.org, oleksandr_tyshchenko@epam.com, iommu@lists.linux.dev, daniel@ffwll.ch, airlied@gmail.com Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" From: Robert Beckett swiotlb_max_segment used to return either the maximum size that swiotlb could bounce, or for Xen PV PAGE_SIZE even if swiotlb could bounce buffer larger mappings. This made i915 on Xen PV work as it bypasses the coherency aspect of the DMA API and can't cope with bounce buffering and this avoided bounce buffering for the Xen/PV case. So instead of adding this hack back, check for Xen/PV directly in i915 for the Xen case and otherwise use the proper DMA API helper to query the maximum mapping size. Replace swiotlb_max_segment() calls with dma_max_mapping_size(). In i915_gem_object_get_pages_internal() no longer consider max_segment only if CONFIG_SWIOTLB is enabled. There can be other (iommu related) causes of specific max segment sizes. Fixes: a2daa27c0c61 ("swiotlb: simplify swiotlb_max_segment") Reported-by: Marek Marczykowski-Górecki Signed-off-by: Robert Beckett Signed-off-by: Christoph Hellwig [hch: added the Xen hack, rewrote the changelog] Reviewed-by: Tvrtko Ursulin --- drivers/gpu/drm/i915/gem/i915_gem_internal.c | 19 +++-------- drivers/gpu/drm/i915/gem/i915_gem_shmem.c | 2 +- drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 4 +-- drivers/gpu/drm/i915/gem/i915_gem_userptr.c | 2 +- drivers/gpu/drm/i915/i915_scatterlist.h | 34 ++++++++++++-------- 5 files changed, 29 insertions(+), 32 deletions(-) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_internal.c b/drivers/gpu/drm/i915/gem/i915_gem_internal.c index c698f95af15fe..629acb403a2c9 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_internal.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_internal.c @@ -6,7 +6,6 @@ #include #include -#include #include "i915_drv.h" #include "i915_gem.h" @@ -38,22 +37,12 @@ static int i915_gem_object_get_pages_internal(struct drm_i915_gem_object *obj) struct scatterlist *sg; unsigned int sg_page_sizes; unsigned int npages; - int max_order; + int max_order = MAX_ORDER; + unsigned int max_segment; gfp_t gfp; - max_order = MAX_ORDER; -#ifdef CONFIG_SWIOTLB - if (is_swiotlb_active(obj->base.dev->dev)) { - unsigned int max_segment; - - max_segment = swiotlb_max_segment(); - if (max_segment) { - max_segment = max_t(unsigned int, max_segment, - PAGE_SIZE) >> PAGE_SHIFT; - max_order = min(max_order, ilog2(max_segment)); - } - } -#endif + max_segment = i915_sg_segment_size(i915->drm.dev) >> PAGE_SHIFT; + max_order = min(max_order, get_order(max_segment)); gfp = GFP_KERNEL | __GFP_HIGHMEM | __GFP_RECLAIMABLE; if (IS_I965GM(i915) || IS_I965G(i915)) { diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c index f42ca1179f373..11125c32dd35d 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c @@ -194,7 +194,7 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj) struct intel_memory_region *mem = obj->mm.region; struct address_space *mapping = obj->base.filp->f_mapping; const unsigned long page_count = obj->base.size / PAGE_SIZE; - unsigned int max_segment = i915_sg_segment_size(); + unsigned int max_segment = i915_sg_segment_size(i915->drm.dev); struct sg_table *st; struct sgt_iter sgt_iter; struct page *page; diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c index 4f861782c3e85..a4aa9500fa179 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c @@ -189,7 +189,7 @@ static int i915_ttm_tt_shmem_populate(struct ttm_device *bdev, struct drm_i915_private *i915 = container_of(bdev, typeof(*i915), bdev); struct intel_memory_region *mr = i915->mm.regions[INTEL_MEMORY_SYSTEM]; struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm); - const unsigned int max_segment = i915_sg_segment_size(); + const unsigned int max_segment = i915_sg_segment_size(i915->drm.dev); const size_t size = (size_t)ttm->num_pages << PAGE_SHIFT; struct file *filp = i915_tt->filp; struct sgt_iter sgt_iter; @@ -538,7 +538,7 @@ static struct i915_refct_sgt *i915_ttm_tt_get_st(struct ttm_tt *ttm) ret = sg_alloc_table_from_pages_segment(st, ttm->pages, ttm->num_pages, 0, (unsigned long)ttm->num_pages << PAGE_SHIFT, - i915_sg_segment_size(), GFP_KERNEL); + i915_sg_segment_size(i915_tt->dev), GFP_KERNEL); if (ret) { st->sgl = NULL; return ERR_PTR(ret); diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c index d4398948f0162..f34e01a7fefb9 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c @@ -129,7 +129,7 @@ static void i915_gem_object_userptr_drop_ref(struct drm_i915_gem_object *obj) static int i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj) { const unsigned long num_pages = obj->base.size >> PAGE_SHIFT; - unsigned int max_segment = i915_sg_segment_size(); + unsigned int max_segment = i915_sg_segment_size(obj->base.dev->dev); struct sg_table *st; unsigned int sg_page_sizes; struct page **pvec; diff --git a/drivers/gpu/drm/i915/i915_scatterlist.h b/drivers/gpu/drm/i915/i915_scatterlist.h index 9ddb3e743a3e5..b0a1db44f8950 100644 --- a/drivers/gpu/drm/i915/i915_scatterlist.h +++ b/drivers/gpu/drm/i915/i915_scatterlist.h @@ -9,7 +9,8 @@ #include #include -#include +#include +#include #include "i915_gem.h" @@ -127,19 +128,26 @@ static inline unsigned int i915_sg_dma_sizes(struct scatterlist *sg) return page_sizes; } -static inline unsigned int i915_sg_segment_size(void) +static inline unsigned int i915_sg_segment_size(struct device *dev) { - unsigned int size = swiotlb_max_segment(); - - if (size == 0) - size = UINT_MAX; - - size = rounddown(size, PAGE_SIZE); - /* swiotlb_max_segment_size can return 1 byte when it means one page. */ - if (size < PAGE_SIZE) - size = PAGE_SIZE; - - return size; + size_t max = min_t(size_t, UINT_MAX, dma_max_mapping_size(dev)); + + /* + * For Xen PV guests pages aren't contiguous in DMA (machine) address + * space. The DMA API takes care of that both in dma_alloc_* (by + * calling into the hypervisor to make the pages contiguous) and in + * dma_map_* (by bounce buffering). But i915 abuses ignores the + * coherency aspects of the DMA API and thus can't cope with bounce + * buffering actually happening, so add a hack here to force small + * allocations and mappings when running in PV mode on Xen. + * + * Note this will still break if bounce buffering is required for other + * reasons, like confidential computing hypervisors or PCIe root ports + * with addressing limitations. + */ + if (xen_pv_domain()) + max = PAGE_SIZE; + return round_down(max, PAGE_SIZE); } bool i915_sg_trim(struct sg_table *orig_st);