Re: [PATCH 1/5] Add pagetable allocation notifiers

[Chris Wright <chrisw@osdl.org>]

* Zachary Amsden (zach@vmware.com) wrote:
> Chris Wright wrote:
> 
> >* Zachary Amsden (zach@vmware.com) wrote:
> > 
> >
> >>--- linux-2.6.13.orig/arch/i386/mm/init.c	2005-08-24 
> >>09:31:05.000000000 -0700
> >>+++ linux-2.6.13/arch/i386/mm/init.c	2005-08-24 09:31:31.000000000 -0700
> >>@@ -79,6 +79,7 @@ static pte_t * __init one_page_table_ini
> >>{
> >>	if (pmd_none(*pmd)) {
> >>		pte_t *page_table = (pte_t *) 
> >>		alloc_bootmem_low_pages(PAGE_SIZE);
> >>+		SetPagePTE(virt_to_page(page_table));
> >>   
> >>
> >
> >Xen has this on one_md_table_init() as well for pmd.
> >
> > 
> >
> >>		set_pmd(pmd, __pmd(__pa(page_table) | _PAGE_TABLE));
> >>		if (page_table != pte_offset_kernel(pmd, 0))
> >>			BUG();	
> >>Index: linux-2.6.13/arch/i386/mm/pageattr.c
> >>===================================================================
> >>--- linux-2.6.13.orig/arch/i386/mm/pageattr.c	2005-08-24 
> >>09:31:05.000000000 -0700
> >>+++ linux-2.6.13/arch/i386/mm/pageattr.c	2005-08-24 
> >>09:31:31.000000000 -0700
> >>@@ -52,8 +52,9 @@ static struct page *split_large_page(uns
> >>	address = __pa(address);
> >>	addr = address & LARGE_PAGE_MASK; 
> >>	pbase = (pte_t *)page_address(base);
> >>+	SetPagePTE(virt_to_page(pbase));
> >>	for (i = 0; i < PTRS_PER_PTE; i++, addr += PAGE_SIZE) {
> >>-               set_pte(&pbase[i], pfn_pte(addr >> PAGE_SHIFT,
> >>+		set_pte(&pbase[i], pfn_pte(addr >> PAGE_SHIFT,
> >>   
> >>
> >
> >No need to intersperse whitespace cleanups.
> >
> > 
> >
> >>                                          addr == address ? prot : 
> >>                                          PAGE_KERNEL));
> >>	}
> >>	return base;
> >>@@ -146,6 +147,7 @@ __change_page_attr(struct page *page, pg
> >>		BUG_ON(!page_count(kpte_page));
> >>
> >>		if (cpu_has_pse && (page_count(kpte_page) == 1)) {
> >>+			ClearPagePTE(virt_to_page(kpte));
> >>			list_add(&kpte_page->lru, &df_list);
> >>			revert_page(kpte_page, address);
> >>		}
> >>Index: linux-2.6.13/arch/i386/mm/pgtable.c
> >>===================================================================
> >>--- linux-2.6.13.orig/arch/i386/mm/pgtable.c	2005-08-24 
> >>09:31:05.000000000 -0700
> >>+++ linux-2.6.13/arch/i386/mm/pgtable.c	2005-08-24 
> >>09:40:22.000000000 -0700
> >>@@ -209,6 +209,7 @@ void pgd_ctor(void *pgd, kmem_cache_t *c
> >>
> >>	if (PTRS_PER_PMD == 1) {
> >>		memset(pgd, 0, USER_PTRS_PER_PGD*sizeof(pgd_t));
> >>+		SetPagePDE(virt_to_page(pgd));
> >>		spin_lock_irqsave(&pgd_lock, flags);
> >>	}
> >>
> >>@@ -227,6 +228,7 @@ void pgd_dtor(void *pgd, kmem_cache_t *c
> >>{
> >>	unsigned long flags; /* can be called from interrupt context */
> >>
> >>+	ClearPagePDE(virt_to_page(pgd));
> >>   
> >>
> >
> >This reminds me, Xen had some unconditional use of pgd_dtor I need
> >to go back and look at.
> > 
> >
> 
> It looks quite unneeded:
> 
> void pgd_dtor(void *pgd, kmem_cache_t *cache, unsigned long unused)
> {
>        unsigned long flags; /* can be called from interrupt context */
> 
>        if (HAVE_SHARED_KERNEL_PMD)  <--- /* PAE */
>                return;

Yeah, that's not quite the case:

include/asm-xen/asm-i386/pgtable-3level-defs.h:#define HAVE_SHARED_KERNEL_PMD 0
include/asm-xen/asm-i386/pgtable-2level-defs.h:#define HAVE_SHARED_KERNEL_PMD 0