[Nouveau] [Patch RFC] ttm: nouveau accelerated on Xen pv-ops kernel
arvino55 at gmail.com
Fri Mar 12 04:45:57 PST 2010
On Thu, Mar 11, 2010 at 4:32 PM, Pekka Paalanen <pq at iki.fi> wrote:
> I'm adding dri-devel@ to CC, since this suggested patch touches
> TTM code, and none of the Nouveau code. TTM patches go via
> dri-devel at .
> On Wed, 10 Mar 2010 18:51:21 +0530
> Arvind R <arvino55 at gmail.com> wrote:
>> Following is a simple patch that is needed in nouveau to get
>> accelerated X on a Xen dom0 pv_ops kernel. The kernel is jeremy's
>> 184.108.40.206 as of 20100222. The whole gpu tree of nouveau (which is
>> almost the mainline merge), was substituted into the kernel-tree.
>> All components of X (mesa, Xorg-server-7.5, xf86-nouveau, libdrm)
>> used of the same day.
>> diff -Naur nouveau-kernel.orig/drivers/gpu/drm/ttm/ttm_bo_vm.c
>> --- nouveau-kernel.orig/drivers/gpu/drm/ttm/ttm_bo_vm.c 2010-01-27
>> 10:19:28.000000000 +0530
>> +++ nouveau-kernel.new/drivers/gpu/drm/ttm/ttm_bo_vm.c 2010-03-10
>> 17:28:59.000000000 +0530
>> @@ -271,7 +271,10 @@
>> vma->vm_private_data = bo;
>> - vma->vm_flags |= VM_RESERVED | VM_IO | VM_MIXEDMAP |
>> + vma->vm_flags |= VM_RESERVED | VM_MIXEDMAP |
>> + if (!((bo->mem.placement & TTM_PL_MASK_MEM) &
>> + vma->vm_flags |= VM_IO;
>> + vma->vm_page_prot = vma_get_vm_prot(vma->vm_flags);
>> return 0;
sorry for the typo and other procedural errors.
the last added line should be
+ vma->vm_page_prot = vm_get_page_prot(vma->vm_flags)
>> This patch is necessary because, in Xen, PFN of a page is
>> virtualised. So physical addresses
>> for DMA programming needs to use the MFN. Xen transparently does
>> the correct translation
>> using the _PAGE_IOMEM prot-bit in the PTE. If the bit is set,
>> then Xen assumes that the backing
>> memory is in the IOMEM space, and PFN equals MFN. If not set,
>> page_to_pfn() returns MFN.
>> The patch enables the ttm_bo_vm_fault() handler to behave
>> correctly under Xen, and has no
>> side-effects on normal (not under Xen) operations. The use of
>> TTM_PL_FLAG_TT in the
>> check assumes that all other placements are backed by device
>> memory or IO. If there are
>> any other placements that use system memory, that flag has to be
>> OR'ed into the check.
>> The above patch has no implications on a normal kernel or a Xen
>> pv_ops kernel booted without
>> the Xen hypervisor. My testing is on a debian-lenny environment
>> on a Core2 processor with
>> nVidia GeForce 9400 GT.
Efficacy of patch:
successful flightgear run on dom0 AND bareboot!
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