On Wed, Apr 7, 2010 at 8:21 PM, Jerome Glisse <jgli...@redhat.com> wrote:
> On fault the driver is given the opportunity to perform any operation
> it sees fit in order to place the buffer into a CPU visible area of
> memory. This patch doesn't break TTM users, nouveau, vmwgfx and radeon
> should keep working properly. Future patch will take advantage of this
> infrastructure and remove the old path from TTM once driver are
> converted.
>
> V2 return VM_FAULT_NOPAGE if callback return -EBUSY or -ERESTARTSYS
> V3 balance io_mem_reserve and io_mem_free call, fault_reserve_notify
> is responsible to perform any necessary task for mapping to succeed
> V4 minor cleanup, atomic_t -> bool as member is protected by reserve
> mecanism from concurent access
> V5 the callback is now responsible for iomapping the bo and providing
> a virtual address this simplify TTM and will allow to get rid of
> TTM_MEMTYPE_FLAG_NEEDS_IOREMAP
Okay I've applied all these to drm-next and it fails to run X for longer than
5 mins on my 32-bit machine.
The whole IO reserve thing looks like a bad idea for anything but kmap,
since it ioremap's the pages, but we have limited ioremap space on 32-bit,
and you hit that and vmallocs all start failing soon after.
>
> - ret = ttm_bo_pci_offset(bdev, &bo->mem, &bus_base, &bus_offset,
> - &bus_size);
> - if (unlikely(ret != 0)) {
> + ret = ttm_mem_io_reserve(bdev, &bo->mem);
> + if (ret) {
> retval = VM_FAULT_SIGBUS;
> goto out_unlock;
> }
This is the start of the insanity, since ever bo that takes a
userspace pagefault
ends up using ioremap space for *no* reason whatsoever at all. You only need
to use ioremap space if the *kernel* is accessing the bo not if userspace is,
so really only in the kmap space.
I've dropped it all from drm-next until you can resolve this.
Dave.
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