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

[Zachary Amsden <zach@vmware.com>]

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;

       spin_lock_irqsave(&pgd_lock, flags);
       pgd_list_del(pgd);
       spin_unlock_irqrestore(&pgd_lock, flags);
}

Leaving the dtor conditional saves an indirect function call ;)

Zach
-
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