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Message-ID: <20190719092153.GJ15868@phenom.ffwll.local>
Date: Fri, 19 Jul 2019 11:21:53 +0200
From: Daniel Vetter <daniel@...ll.ch>
To: Rob Clark <robdclark@...il.com>
Cc: dri-devel@...ts.freedesktop.org,
Rob Clark <robdclark@...omium.org>,
David Airlie <airlied@...ux.ie>,
Daniel Vetter <daniel@...ll.ch>,
Emil Velikov <emil.velikov@...labora.com>,
Chris Wilson <chris@...is-wilson.co.uk>,
Eric Anholt <eric@...olt.net>,
Thomas Zimmermann <tzimmermann@...e.de>,
Imre Deak <imre.deak@...el.com>,
Deepak Sharma <deepak.sharma@....com>,
Eric Biggers <ebiggers@...gle.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/vgem: fix cache synchronization on arm/arm64
On Wed, Jul 17, 2019 at 02:15:37PM -0700, Rob Clark wrote:
> From: Rob Clark <robdclark@...omium.org>
>
> drm_cflush_pages() is no-op on arm/arm64. But instead we can use
> dma_sync API.
>
> Fixes failures w/ vgem_test.
>
> Signed-off-by: Rob Clark <robdclark@...omium.org>
> ---
> An alternative approach to the series[1] I sent yesterday
>
> On the plus side, it keeps the WC buffers and avoids any drm core
> changes. On the minus side, I don't think it will work (at least
> on arm64) prior to v5.0[2], so the fix can't be backported very
> far.
Yeah seems a lot more reasonable.
Acked-by: Daniel Vetter <daniel.vetter@...ll.ch>
>
> [1] https://patchwork.freedesktop.org/series/63771/
> [2] depends on 356da6d0cde3323236977fce54c1f9612a742036
>
> drivers/gpu/drm/vgem/vgem_drv.c | 130 ++++++++++++++++++++------------
> 1 file changed, 83 insertions(+), 47 deletions(-)
>
> diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c
> index 76d95b5e289c..6c9b5e20b3d4 100644
> --- a/drivers/gpu/drm/vgem/vgem_drv.c
> +++ b/drivers/gpu/drm/vgem/vgem_drv.c
> @@ -47,10 +47,16 @@ static struct vgem_device {
> struct platform_device *platform;
> } *vgem_device;
>
> +static void sync_and_unpin(struct drm_vgem_gem_object *bo);
> +static struct page **pin_and_sync(struct drm_vgem_gem_object *bo);
> +
> static void vgem_gem_free_object(struct drm_gem_object *obj)
> {
> struct drm_vgem_gem_object *vgem_obj = to_vgem_bo(obj);
>
> + if (!obj->import_attach)
> + sync_and_unpin(vgem_obj);
> +
> kvfree(vgem_obj->pages);
> mutex_destroy(&vgem_obj->pages_lock);
>
> @@ -78,40 +84,15 @@ static vm_fault_t vgem_gem_fault(struct vm_fault *vmf)
> return VM_FAULT_SIGBUS;
>
> mutex_lock(&obj->pages_lock);
> + if (!obj->pages)
> + pin_and_sync(obj);
> if (obj->pages) {
> get_page(obj->pages[page_offset]);
> vmf->page = obj->pages[page_offset];
> ret = 0;
> }
> mutex_unlock(&obj->pages_lock);
> - if (ret) {
> - struct page *page;
> -
> - page = shmem_read_mapping_page(
> - file_inode(obj->base.filp)->i_mapping,
> - page_offset);
> - if (!IS_ERR(page)) {
> - vmf->page = page;
> - ret = 0;
> - } else switch (PTR_ERR(page)) {
> - case -ENOSPC:
> - case -ENOMEM:
> - ret = VM_FAULT_OOM;
> - break;
> - case -EBUSY:
> - ret = VM_FAULT_RETRY;
> - break;
> - case -EFAULT:
> - case -EINVAL:
> - ret = VM_FAULT_SIGBUS;
> - break;
> - default:
> - WARN_ON(PTR_ERR(page));
> - ret = VM_FAULT_SIGBUS;
> - break;
> - }
>
> - }
> return ret;
> }
>
> @@ -277,32 +258,93 @@ static const struct file_operations vgem_driver_fops = {
> .release = drm_release,
> };
>
> -static struct page **vgem_pin_pages(struct drm_vgem_gem_object *bo)
> +/* Called under pages_lock, except in free path (where it can't race): */
> +static void sync_and_unpin(struct drm_vgem_gem_object *bo)
> {
> - mutex_lock(&bo->pages_lock);
> - if (bo->pages_pin_count++ == 0) {
> - struct page **pages;
> + struct drm_device *dev = bo->base.dev;
> +
> + if (bo->table) {
> + dma_sync_sg_for_cpu(dev->dev, bo->table->sgl,
> + bo->table->nents, DMA_BIDIRECTIONAL);
> + sg_free_table(bo->table);
> + kfree(bo->table);
> + bo->table = NULL;
> + }
> +
> + if (bo->pages) {
> + drm_gem_put_pages(&bo->base, bo->pages, true, true);
> + bo->pages = NULL;
> + }
> +}
> +
> +static struct page **pin_and_sync(struct drm_vgem_gem_object *bo)
> +{
> + struct drm_device *dev = bo->base.dev;
> + int npages = bo->base.size >> PAGE_SHIFT;
> + struct page **pages;
> + struct sg_table *sgt;
> +
> + WARN_ON(!mutex_is_locked(&bo->pages_lock));
> +
> + pages = drm_gem_get_pages(&bo->base);
> + if (IS_ERR(pages)) {
> + bo->pages_pin_count--;
> + mutex_unlock(&bo->pages_lock);
> + return pages;
> + }
>
> - pages = drm_gem_get_pages(&bo->base);
> - if (IS_ERR(pages)) {
> - bo->pages_pin_count--;
> - mutex_unlock(&bo->pages_lock);
> - return pages;
> - }
> + sgt = drm_prime_pages_to_sg(pages, npages);
> + if (IS_ERR(sgt)) {
> + dev_err(dev->dev,
> + "failed to allocate sgt: %ld\n",
> + PTR_ERR(bo->table));
> + drm_gem_put_pages(&bo->base, pages, false, false);
> + mutex_unlock(&bo->pages_lock);
> + return ERR_CAST(bo->table);
> + }
> +
> + /*
> + * Flush the object from the CPU cache so that importers
> + * can rely on coherent indirect access via the exported
> + * dma-address.
> + */
> + dma_sync_sg_for_device(dev->dev, sgt->sgl,
> + sgt->nents, DMA_BIDIRECTIONAL);
> +
> + bo->pages = pages;
> + bo->table = sgt;
> +
> + return pages;
> +}
> +
> +static struct page **vgem_pin_pages(struct drm_vgem_gem_object *bo)
> +{
> + struct page **pages;
>
> - bo->pages = pages;
> + mutex_lock(&bo->pages_lock);
> + if (bo->pages_pin_count++ == 0 && !bo->pages) {
> + pages = pin_and_sync(bo);
> + } else {
> + WARN_ON(!bo->pages);
> + pages = bo->pages;
> }
> mutex_unlock(&bo->pages_lock);
>
> - return bo->pages;
> + return pages;
> }
>
> static void vgem_unpin_pages(struct drm_vgem_gem_object *bo)
> {
> + /*
> + * We shouldn't hit this for imported bo's.. in the import
> + * case we don't own the scatter-table
> + */
> + WARN_ON(bo->base.import_attach);
> +
> mutex_lock(&bo->pages_lock);
> if (--bo->pages_pin_count == 0) {
> - drm_gem_put_pages(&bo->base, bo->pages, true, true);
> - bo->pages = NULL;
> + WARN_ON(!bo->table);
> + sync_and_unpin(bo);
> }
> mutex_unlock(&bo->pages_lock);
> }
> @@ -310,18 +352,12 @@ static void vgem_unpin_pages(struct drm_vgem_gem_object *bo)
> static int vgem_prime_pin(struct drm_gem_object *obj)
> {
> struct drm_vgem_gem_object *bo = to_vgem_bo(obj);
> - long n_pages = obj->size >> PAGE_SHIFT;
> struct page **pages;
>
> pages = vgem_pin_pages(bo);
> if (IS_ERR(pages))
> return PTR_ERR(pages);
>
> - /* Flush the object from the CPU cache so that importers can rely
> - * on coherent indirect access via the exported dma-address.
> - */
> - drm_clflush_pages(pages, n_pages);
> -
> return 0;
> }
>
> --
> 2.21.0
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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