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[POWERPC] Small fixes & cleanups in segment page size demotion

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The code for demoting segments to 4K had some issues, like for example,
when using _PAGE_4K_PFN flag, the first CPU to hit it would do the
demotion, but other CPUs hitting the same page wouldn't properly flush
their SLBs if mmu_ci_restriction isn't set.  There are also potential
issues with hash_preload not handling _PAGE_4K_PFN.  All of these are
non issues on current hardware but might bite us in the future.

This patch thus fixes it by:

 - Taking the test comparing the mm and current CPU context page
sizes to decide to flush SLBs out of the mmu_ci_restrictions test
since that can also be triggered by _PAGE_4K_PFN pages

 - Due to the above being done all the time, demote_segment_4k
doesn't need update the context and flush the SLB

 - demote_segment_4k can be static and doesn't need an EXPORT_SYMBOL

 - Making hash_preload ignore anything that has either _PAGE_4K_PFN
or _PAGE_NO_CACHE set, thus avoiding duplication of the complicated
logic in hash_page() (and possibly making hash_preload a little bit
faster for the normal case).

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
Benjamin Herrenschmidt 2007-05-08 16:27:27 +10:00 committed by Paul Mackerras
parent b15f792faf
commit 16f1c74675
1 changed files with 46 additions and 41 deletions
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45
arch/powerpc/mm/hash_utils_64.c
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@ -596,22 +596,18 @@ unsigned int hash_page_do_lazy_icache(unsigned int pp, pte_t pte, int trap)
* Demote a segment to using 4k pages.
* For now this makes the whole process use 4k pages.
*/
void demote_segment_4k(struct mm_struct *mm, unsigned long addr)
{
#ifdef CONFIG_PPC_64K_PAGES
static void demote_segment_4k(struct mm_struct *mm, unsigned long addr)
{
if (mm->context.user_psize == MMU_PAGE_4K)
return;
mm->context.user_psize = MMU_PAGE_4K;
mm->context.sllp = SLB_VSID_USER | mmu_psize_defs[MMU_PAGE_4K].sllp;
get_paca()->context = mm->context;
slb_flush_and_rebolt();
#ifdef CONFIG_SPE_BASE
spu_flush_all_slbs(mm);
#endif
#endif
}
EXPORT_SYMBOL_GPL(demote_segment_4k);
#endif /* CONFIG_PPC_64K_PAGES */
/* Result code is:
* 0 - handled
@ -711,9 +707,10 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
psize = MMU_PAGE_4K;
}
if (mmu_ci_restrictions) {
/* If this PTE is non-cacheable, switch to 4k */
if (psize == MMU_PAGE_64K &&
/* If this PTE is non-cacheable and we have restrictions on
* using non cacheable large pages, then we switch to 4k
*/
if (mmu_ci_restrictions && psize == MMU_PAGE_64K &&
(pte_val(*ptep) & _PAGE_NO_CACHE)) {
if (user_region) {
demote_segment_4k(mm, ea);
@ -728,14 +725,15 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
"to 4kB pages because of "
"non-cacheable mapping\n");
psize = mmu_vmalloc_psize = MMU_PAGE_4K;
}
#ifdef CONFIG_SPE_BASE
spu_flush_all_slbs(mm);
#endif
}
}
if (user_region) {
if (psize != get_paca()->context.user_psize) {
get_paca()->context = mm->context;
get_paca()->context.user_psize =
mm->context.user_psize;
slb_flush_and_rebolt();
}
} else if (get_paca()->vmalloc_sllp !=
@ -744,7 +742,7 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap)
mmu_psize_defs[mmu_vmalloc_psize].sllp;
slb_flush_and_rebolt();
}
}
if (psize == MMU_PAGE_64K)
rc = __hash_page_64K(ea, access, vsid, ptep, trap, local);
else
@ -780,13 +778,26 @@ void hash_preload(struct mm_struct *mm, unsigned long ea,
DBG_LOW("hash_preload(mm=%p, mm->pgdir=%p, ea=%016lx, access=%lx,"
" trap=%lx\n", mm, mm->pgd, ea, access, trap);
/* Get PTE, VSID, access mask */
/* Get Linux PTE if available */
pgdir = mm->pgd;
if (pgdir == NULL)
return;
ptep = find_linux_pte(pgdir, ea);
if (!ptep)
return;
#ifdef CONFIG_PPC_64K_PAGES
/* If either _PAGE_4K_PFN or _PAGE_NO_CACHE is set (and we are on
* a 64K kernel), then we don't preload, hash_page() will take
* care of it once we actually try to access the page.
* That way we don't have to duplicate all of the logic for segment
* page size demotion here
*/
if (pte_val(*ptep) & (_PAGE_4K_PFN | _PAGE_NO_CACHE))
return;
#endif /* CONFIG_PPC_64K_PAGES */
/* Get VSID */
vsid = get_vsid(mm->context.id, ea);
/* Hash it in */
@ -797,12 +808,6 @@ void hash_preload(struct mm_struct *mm, unsigned long ea,
#ifndef CONFIG_PPC_64K_PAGES
__hash_page_4K(ea, access, vsid, ptep, trap, local);
#else
if (mmu_ci_restrictions) {
/* If this PTE is non-cacheable, switch to 4k */
if (mm->context.user_psize == MMU_PAGE_64K &&
(pte_val(*ptep) & _PAGE_NO_CACHE))
demote_segment_4k(mm, ea);
}
if (mm->context.user_psize == MMU_PAGE_64K)
__hash_page_64K(ea, access, vsid, ptep, trap, local);
else