Messages in this thread | | | Date | Thu, 23 Oct 2008 13:38:40 -0700 | From | Andrew Morton <> | Subject | Re: Adding kmap_atomic_prot_pfn (was: [git pull] drm patches for 2.6.27-rc1) |
| |
On Thu, 23 Oct 2008 13:22:12 -0700 Keith Packard <keithp@keithp.com> wrote:
> We just ran some numbers on a box with PAT enabled and broken MTRRs. > Finally we have a test platform for the difference between kmap_atomic > and kmap_atomic_prot. Using regular kmap_atomic on this platform, we get > UC access to the graphics device; sending data from the CPU is a bit > slow. Adding kmap_atomic_prot_pfn and specifying WC access raises that > by a fairly significant factor, taking our CPU utilization for > copy_from_user from 40% to 2%. > > Here's a patch which adds kmap_atomic_prot_pfn to the kernel for this > usage. When we add native io-mapping support instead of sitting on top > of kmap, we can remove this function. > > I've reworked the io_mapping patches to use this function as well, along > with cleaning up the i915 code along the lines of Linus' current > version. I'll post those if this patch looks acceptable. > > From e3f633dcb36889fa85ea06cca339072df3c44ae0 Mon Sep 17 00:00:00 2001 > From: Keith Packard <keithp@keithp.com> > Date: Thu, 23 Oct 2008 11:53:45 -0700 > Subject: [PATCH] Add kmap_atomic_prot_pfn > > kmap_atomic_prot_pfn is a mixture of kmap_atomic_prot and kmap_atomic_pfn, > accepting both a pfn instead of a page and an explicit protection value. > > Signed-off-by: Keith Packard <keithp@keithp.com> > --- > arch/x86/mm/highmem_32.c | 19 +++++++++++++++++++ > include/asm-x86/highmem.h | 1 + > include/linux/highmem.h | 1 + > 3 files changed, 21 insertions(+), 0 deletions(-) > > diff --git a/arch/x86/mm/highmem_32.c b/arch/x86/mm/highmem_32.c > index bcc079c..91ae5e8 100644 > --- a/arch/x86/mm/highmem_32.c > +++ b/arch/x86/mm/highmem_32.c > @@ -139,6 +139,25 @@ void *kmap_atomic_pfn(unsigned long pfn, enum km_type type) > } > EXPORT_SYMBOL_GPL(kmap_atomic_pfn); /* temporarily in use by i915 GEM until vmap */ > > +/* This is the same as kmap_atomic_prot() but can map memory that doesn't > + * have a struct page associated with it. > + */ > +void *kmap_atomic_prot_pfn(unsigned long pfn, enum km_type type, pgprot_t prot) > +{ > + enum fixed_addresses idx; > + unsigned long vaddr; > + > + pagefault_disable(); > + > + idx = type + KM_TYPE_NR*smp_processor_id(); > + vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx); > + set_pte(kmap_pte-idx, pfn_pte(pfn, prot)); > + arch_flush_lazy_mmu_mode(); > + > + return (void*) vaddr; > +} > +EXPORT_SYMBOL_GPL(kmap_atomic_prot_pfn); /* temporarily in use by i915 GEM until vmap */
I guess one could reimplemenet kmap_atomic_pfn() to call this. Sometime.
> struct page *kmap_atomic_to_page(void *ptr) > { > unsigned long idx, vaddr = (unsigned long)ptr; > diff --git a/include/asm-x86/highmem.h b/include/asm-x86/highmem.h > index bc3f6a2..a1f8f8c 100644 > --- a/include/asm-x86/highmem.h > +++ b/include/asm-x86/highmem.h > @@ -66,6 +66,7 @@ void *kmap_atomic_prot(struct page *page, enum km_type type, pgprot_t prot); > void *kmap_atomic(struct page *page, enum km_type type); > void kunmap_atomic(void *kvaddr, enum km_type type); > void *kmap_atomic_pfn(unsigned long pfn, enum km_type type); > +void *kmap_atomic_prot_pfn(unsigned long pfn, enum km_type type, pgprot_t prot);
Given that all highmem-implementing archtiectures must use the same declaration here, we might as well put it into include/linux/highmem.h. Although that goes against current mistakes^Wcode.
Does powerpc32 still implement highmem? It seems that way. You broke it, no?
| |