On 9/9/2015 11:33 AM, Chris Wilson wrote:
On Wed, Sep 09, 2015 at 11:29:52AM +0100, Michel Thierry wrote:
i915_gem_object_bind_to_vm returns -E2BIG when the user tries to bind an
object larger than the aperture, but i915_gem_fault does not handle this
return code:
[501906.530985] gem_mmap_gtt: starting subtest big-bo-tiledX
[501906.541992] gem_mmap_gtt (22362): drop_caches: 3
[501906.610774] WARNING: CPU: 2 PID: 22362 at
drivers/gpu/drm/i915/i915_gem.c:1880 i915_gem_fault+0x24f/0x470 [i915]()
[501906.623568] unhandled error in i915_gem_fault: -7
[501906.825115] Call Trace:
[501906.830322] [<ffffffff8178ffcc>] dump_stack+0x45/0x57
[501906.838589] [<ffffffff810759aa>] warn_slowpath_common+0x8a/0xc0
[501906.847846] [<ffffffff81075a26>] warn_slowpath_fmt+0x46/0x50
[501906.856776] [<ffffffffc079591f>] i915_gem_fault+0x24f/0x470 [i915]
[501906.866276] [<ffffffff8119e11d>] __do_fault+0x3d/0xa0
[501906.874464] [<ffffffff81068cc0>] ? pte_alloc_one+0x30/0x50
[501906.883169] [<ffffffff811a26a7>] handle_mm_fault+0xe27/0x1810
[501906.892202] [<ffffffff81306e8a>] ? security_mmap_file+0xca/0xe0
[501906.900389] [<ffffffff811fb6ad>] ? do_vfs_ioctl+0x2cd/0x4b0
[501906.908143] [<ffffffff81063ada>] __do_page_fault+0x19a/0x430
[501906.916024] [<ffffffff81063d92>] do_page_fault+0x22/0x30
[501906.923532] [<ffffffff81799248>] page_fault+0x28/0x30
RFC about the error code that should be returned by i915_gem_fault.
There are two fixes here, change E2BIG to ENOSPC. The differentiate is
painful to all consumers (and missing in userspace).
I'll change the return code in gem_object_bind_to_vm instead.
The second is that gem_fault was supposed to be fixed to handle it and
sigbus is the legimate error for that case (not enomem/sigsegv).
These subtests use objs tiling x/y, so the driver won't use partial views.
Should it be better if i915_gem_mmap_gtt checks for this (obj size
bigger than apperture and some tiling mode), and return an error at that
point? Instead of waiting for the sigbus error in gem_fault.
-Michel
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