Messages in this thread | | | Date | Thu, 30 Jul 2009 19:00:09 +0300 | From | Pekka Paalanen <> | Subject | Re: [PATCH 2/2] ttm: Fix ttm in-kernel copying of pages with non-standard caching attributes. |
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Hi,
since I see this patch in Linus' tree, and I likely have to patch TTM in Nouveau's compat-branch to compile with older kernels, I have a question below.
(The Nouveau kernel tree's compat branch offers drm.ko, ttm.ko and nouveau.ko to be built against kernels 2.6.28 and later.)
On Fri, 24 Jul 2009 09:57:34 +0200 Thomas Hellstrom <thellstrom@vmware.com> wrote:
> For x86 this affected highmem pages only, since they were always kmapped > cache-coherent, and this is fixed using kmap_atomic_prot(). > > For other architectures that may not modify the linear kernel map we > resort to vmap() for now, since kmap_atomic_prot() generally uses the > linear kernel map for lowmem pages. This of course comes with a > performance impact and should be optimized when possible. > > Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com> > --- > drivers/gpu/drm/ttm/ttm_bo_util.c | 63 ++++++++++++++++++++++++++++++------ > 1 files changed, 52 insertions(+), 11 deletions(-) > > diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c > index 3e5d0c4..ce2e6f3 100644 > --- a/drivers/gpu/drm/ttm/ttm_bo_util.c > +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c > @@ -136,7 +136,8 @@ static int ttm_copy_io_page(void *dst, void *src, unsigned long page) > } > > static int ttm_copy_io_ttm_page(struct ttm_tt *ttm, void *src, > - unsigned long page) > + unsigned long page, > + pgprot_t prot) > { > struct page *d = ttm_tt_get_page(ttm, page); > void *dst; > @@ -145,17 +146,35 @@ static int ttm_copy_io_ttm_page(struct ttm_tt *ttm, void *src, > return -ENOMEM; > > src = (void *)((unsigned long)src + (page << PAGE_SHIFT)); > - dst = kmap(d); > + > +#ifdef CONFIG_X86 > + dst = kmap_atomic_prot(d, KM_USER0, prot); > +#else > + if (prot != PAGE_KERNEL) > + dst = vmap(&d, 1, 0, prot); > + else > + dst = kmap(d); > +#endif
What are the implications of choosing the non-CONFIG_X86 path even on x86?
Is kmap_atomic_prot() simply an optimization allowed by the x86 arch, and the alternate way also works, although it uses the precious vmalloc address space?
Since kmap_atomic_prot() is not exported on earlier kernels, I'm tempted to just do the non-CONFIG_X86 path.
> if (!dst) > return -ENOMEM; > > memcpy_fromio(dst, src, PAGE_SIZE); > - kunmap(d); > + > +#ifdef CONFIG_X86 > + kunmap_atomic(dst, KM_USER0); > +#else > + if (prot != PAGE_KERNEL) > + vunmap(dst); > + else > + kunmap(d); > +#endif > + > return 0; > } > > static int ttm_copy_ttm_io_page(struct ttm_tt *ttm, void *dst, > - unsigned long page) > + unsigned long page, > + pgprot_t prot) > { > struct page *s = ttm_tt_get_page(ttm, page); > void *src; > @@ -164,12 +183,28 @@ static int ttm_copy_ttm_io_page(struct ttm_tt *ttm, void *dst, > return -ENOMEM; > > dst = (void *)((unsigned long)dst + (page << PAGE_SHIFT)); > - src = kmap(s); > +#ifdef CONFIG_X86 > + src = kmap_atomic_prot(s, KM_USER0, prot); > +#else > + if (prot != PAGE_KERNEL) > + src = vmap(&s, 1, 0, prot); > + else > + src = kmap(s); > +#endif > if (!src) > return -ENOMEM; > > memcpy_toio(dst, src, PAGE_SIZE); > - kunmap(s); > + > +#ifdef CONFIG_X86 > + kunmap_atomic(src, KM_USER0); > +#else > + if (prot != PAGE_KERNEL) > + vunmap(src); > + else > + kunmap(s); > +#endif > + > return 0; > } > > @@ -214,11 +249,17 @@ int ttm_bo_move_memcpy(struct ttm_buffer_object *bo, > > for (i = 0; i < new_mem->num_pages; ++i) { > page = i * dir + add; > - if (old_iomap == NULL) > - ret = ttm_copy_ttm_io_page(ttm, new_iomap, page); > - else if (new_iomap == NULL) > - ret = ttm_copy_io_ttm_page(ttm, old_iomap, page); > - else > + if (old_iomap == NULL) { > + pgprot_t prot = ttm_io_prot(old_mem->placement, > + PAGE_KERNEL); > + ret = ttm_copy_ttm_io_page(ttm, new_iomap, page, > + prot); > + } else if (new_iomap == NULL) { > + pgprot_t prot = ttm_io_prot(new_mem->placement, > + PAGE_KERNEL); > + ret = ttm_copy_io_ttm_page(ttm, old_iomap, page, > + prot); > + } else > ret = ttm_copy_io_page(new_iomap, old_iomap, page); > if (ret) > goto out1; > -- > 1.6.1.3
Thanks.
-- Pekka Paalanen http://www.iki.fi/pq/
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