From bf72aeba2ffef599d1d386425c9e46b82be657cd Mon Sep 17 00:00:00 2001 From: Paul Mackerras Date: Thu, 15 Jun 2006 10:45:18 +1000 Subject: powerpc: Use 64k pages without needing cache-inhibited large pages Some POWER5+ machines can do 64k hardware pages for normal memory but not for cache-inhibited pages. This patch lets us use 64k hardware pages for most user processes on such machines (assuming the kernel has been configured with CONFIG_PPC_64K_PAGES=y). User processes start out using 64k pages and get switched to 4k pages if they use any non-cacheable mappings. With this, we use 64k pages for the vmalloc region and 4k pages for the imalloc region. If anything creates a non-cacheable mapping in the vmalloc region, the vmalloc region will get switched to 4k pages. I don't know of any driver other than the DRM that would do this, though, and these machines don't have AGP. When a region gets switched from 64k pages to 4k pages, we do not have to clear out all the 64k HPTEs from the hash table immediately. We use the _PAGE_COMBO bit in the Linux PTE to indicate whether the page was hashed in as a 64k page or a set of 4k pages. If hash_page is trying to insert a 4k page for a Linux PTE and it sees that it has already been inserted as a 64k page, it first invalidates the 64k HPTE before inserting the 4k HPTE. The hash invalidation routines also use the _PAGE_COMBO bit, to determine whether to look for a 64k HPTE or a set of 4k HPTEs to remove. With those two changes, we can tolerate a mix of 4k and 64k HPTEs in the hash table, and they will all get removed when the address space is torn down. Signed-off-by: Paul Mackerras --- arch/powerpc/kernel/prom.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'arch/powerpc/kernel/prom.c') diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c index 969f4abcc0be..d77d24a89b39 100644 --- a/arch/powerpc/kernel/prom.c +++ b/arch/powerpc/kernel/prom.c @@ -948,7 +948,10 @@ static struct ibm_pa_feature { {CPU_FTR_CTRL, 0, 0, 3, 0}, {CPU_FTR_NOEXECUTE, 0, 0, 6, 0}, {CPU_FTR_NODSISRALIGN, 0, 1, 1, 1}, +#if 0 + /* put this back once we know how to test if firmware does 64k IO */ {CPU_FTR_CI_LARGE_PAGE, 0, 1, 2, 0}, +#endif }; static void __init check_cpu_pa_features(unsigned long node) -- cgit v1.2.3