From: Gerd Hoffmann <kraxel@redhat.com>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: dri-devel <dri-devel@lists.freedesktop.org>,
Thomas Zimmermann <tzimmermann@suse.de>,
Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Maxime Ripard <maxime.ripard@bootlin.com>,
Sean Paul <sean@poorly.run>, David Airlie <airlied@linux.ie>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4 05/17] drm: add mmap() to drm_gem_object_funcs
Date: Mon, 9 Sep 2019 12:06:53 +0200 [thread overview]
Message-ID: <20190909100653.hyo4psakt3ccfwjk@sirius.home.kraxel.org> (raw)
In-Reply-To: <CAKMK7uHFS8uW15NMEzN92POD2hyhkvKFgePdjgL=D-noUAkq3Q@mail.gmail.com>
Hi,
> > + vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
> > + vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
> > + vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
> > + }
>
> Totally unrelated discussion around HMM lead me to a bit a chase, and
> realizing that we probably want a
>
> WARN_ON(!(vma->vm_flags & VM_SPECIAL));
>
> here, to make sure drivers set at least one of the "this is a special
> vma, don't try to treat it like pagecache/anon memory". Just to be on
> the safe side. Maybe we also want to keep the entire vma->vm_flags
> assignment in the common code, but at least the WARN_ON would be a
> good check I think. Maybe also check for VM_DONTEXPAND while at it
Hmm. VM_SPECIAL is this:
#define VM_SPECIAL (VM_IO | VM_DONTEXPAND | VM_PFNMAP | VM_MIXEDMAP)
Requiring VM_DONTEXPAND makes sense for sure. Dunno about the other
ones. For drm_gem_vram_helper VM_IO + VM_PFNMAP are needed.
But we also have drm_gem_shmem_helper which backs objects with normal
pages. In fact drm_gem_shmem_mmap does this:
/* VM_PFNMAP was set by drm_gem_mmap() */
vma->vm_flags &= ~VM_PFNMAP;
vma->vm_flags |= VM_MIXEDMAP;
include/linux/mm.h isn't very helpful in explaining how VM_MIXEDMAP
should be used, only saying can be both "struct page" and pfnmap, so I'm
not sure why VM_MIXEDMAP is set here, it should always be "struct page"
for shmem, no?
cheers,
Gerd
next prev parent reply other threads:[~2019-09-09 10:06 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190808134417.10610-1-kraxel@redhat.com>
2019-08-08 13:44 ` [PATCH v4 01/17] drm/ttm: turn ttm_bo_device.vma_manager into a pointer Gerd Hoffmann
2019-09-03 9:49 ` Daniel Vetter
2019-08-08 13:44 ` [PATCH v4 02/17] drm/ttm: add gem_ttm_bo_device_init() Gerd Hoffmann
2019-08-08 13:44 ` [PATCH v4 03/17] drm/vram: switch vram helpers to the new gem_ttm_bo_device_init() Gerd Hoffmann
2019-08-08 13:44 ` [PATCH v4 04/17] drm/qxl: switch qxl " Gerd Hoffmann
2019-08-08 13:44 ` [PATCH v4 05/17] drm: add mmap() to drm_gem_object_funcs Gerd Hoffmann
2019-09-03 9:48 ` Daniel Vetter
2019-09-06 12:13 ` Gerd Hoffmann
2019-09-06 13:10 ` Daniel Vetter
2019-09-09 10:06 ` Gerd Hoffmann [this message]
2019-08-08 13:44 ` [PATCH v4 06/17] drm/shmem: switch shmem helper to drm_gem_object_funcs->mmap Gerd Hoffmann
2019-08-08 22:51 ` Rob Herring
2019-08-08 13:44 ` [PATCH v4 07/17] drm/shmem: drop DEFINE_DRM_GEM_SHMEM_FOPS Gerd Hoffmann
2019-08-08 22:51 ` Rob Herring
2019-08-08 13:44 ` [PATCH v4 08/17] drm/ttm: factor out ttm_bo_mmap_vma_setup Gerd Hoffmann
2019-08-08 13:44 ` [PATCH v4 09/17] drm/ttm: add drm_gem_ttm_mmap() Gerd Hoffmann
2019-08-08 13:44 ` [PATCH v4 10/17] drm/vram: switch vram helper to drm_gem_object_funcs->mmap codepath Gerd Hoffmann
2019-08-08 13:44 ` [PATCH v4 11/17] drm/vram: drop verify_access Gerd Hoffmann
2019-08-08 13:44 ` [PATCH v4 12/17] drm: drop DRM_VRAM_MM_FILE_OPERATIONS Gerd Hoffmann
2019-08-08 13:44 ` [PATCH v4 13/17] drm/qxl: use drm_gem_object_funcs Gerd Hoffmann
2019-08-08 13:44 ` [PATCH v4 14/17] drm/qxl: drop qxl_ttm_fault Gerd Hoffmann
2019-08-08 13:44 ` [PATCH v4 15/17] drm/qxl: switch qxl to drm_gem_object_funcs->mmap codepath Gerd Hoffmann
2019-08-08 13:44 ` [PATCH v4 16/17] drm/qxl: drop verify_access Gerd Hoffmann
2019-08-08 13:44 ` [PATCH v4 17/17] drm/qxl: use DEFINE_DRM_GEM_FOPS() Gerd Hoffmann
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