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Date: Tue, 31 Aug 2021 19:09:19 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "rppt@...nel.org" <rppt@...nel.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"peterz@...radead.org" <peterz@...radead.org>, "keescook@...omium.org"
<keescook@...omium.org>, "Weiny, Ira" <ira.weiny@...el.com>,
"linux-hardening@...r.kernel.org" <linux-hardening@...r.kernel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>, "vbabka@...e.cz" <vbabka@...e.cz>,
"x86@...nel.org" <x86@...nel.org>, "akpm@...ux-foundation.org"
<akpm@...ux-foundation.org>, "Williams, Dan J" <dan.j.williams@...el.com>,
"Lutomirski, Andy" <luto@...nel.org>, "kernel-hardening@...ts.openwall.com"
<kernel-hardening@...ts.openwall.com>, "Hansen, Dave"
<dave.hansen@...el.com>, "shakeelb@...gle.com" <shakeelb@...gle.com>
Subject: Re: [RFC PATCH v2 05/19] x86, mm: Use cache of page tables
On Tue, 2021-08-31 at 11:40 +0300, Mike Rapoport wrote:
> On Mon, Aug 30, 2021 at 04:59:13PM -0700, Rick Edgecombe wrote:
<trim>
> >
> > diff --git a/arch/x86/include/asm/pgalloc.h
> > b/arch/x86/include/asm/pgalloc.h
> > index c7ec5bb88334..1ff308ea76cd 100644
> > --- a/arch/x86/include/asm/pgalloc.h
> > +++ b/arch/x86/include/asm/pgalloc.h
> > @@ -7,6 +7,10 @@
> > #include <linux/pagemap.h>
> >
> > #define __HAVE_ARCH_PTE_ALLOC_ONE
> > +#ifdef CONFIG_PKS_PG_TABLES
> > +#define __HAVE_ARCH_FREE_TABLE
> > +#define __HAVE_ARCH_ALLOC_TABLE
>
> I think one define would suffice. If we'd ever have an architecture
> that
> can implement only one of those, we update the ifdefery in
> asm-generic/pgalloc.h
>
Good point, I'll change it.
> > +#endif
> > #define __HAVE_ARCH_PGD_FREE
> > #include <asm-generic/pgalloc.h>
> >
> > @@ -162,7 +166,7 @@ static inline void p4d_free(struct mm_struct
> > *mm, p4d_t *p4d)
> > return;
> >
> > BUG_ON((unsigned long)p4d & (PAGE_SIZE-1));
> > - free_page((unsigned long)p4d);
> > + free_table(virt_to_page(p4d));
> > }
> >
> > extern void ___p4d_free_tlb(struct mmu_gather *tlb, p4d_t *p4d);
>
> ...
>
> > diff --git a/include/asm-generic/pgalloc.h b/include/asm-
> > generic/pgalloc.h
> > index 02932efad3ab..e576c19abc8c 100644
> > --- a/include/asm-generic/pgalloc.h
> > +++ b/include/asm-generic/pgalloc.h
> > @@ -2,11 +2,26 @@
> > #ifndef __ASM_GENERIC_PGALLOC_H
> > #define __ASM_GENERIC_PGALLOC_H
> >
> > +#include <linux/mm.h>
> > +
>
> Why is this required?
>
> > #ifdef CONFIG_MMU
> >
> > #define GFP_PGTABLE_KERNEL (GFP_KERNEL | __GFP_ZERO)
> > #define GFP_PGTABLE_USER (GFP_PGTABLE_KERNEL | __GFP_ACCOUNT)
> >
> > +#ifndef __HAVE_ARCH_ALLOC_TABLE
> > +static inline struct page *alloc_table(gfp_t gfp)
> > +{
> > + return alloc_page(gfp);
> > +}
> > +#else /* __HAVE_ARCH_ALLOC_TABLE */
> > +extern struct page *alloc_table(gfp_t gfp);
> > +#endif /* __HAVE_ARCH_ALLOC_TABLE */
> > +
> > +#ifdef __HAVE_ARCH_FREE_TABLE
> > +extern void free_table(struct page *);
> > +#endif /* __HAVE_ARCH_FREE_TABLE */
> > +
> > /**
> > * __pte_alloc_one_kernel - allocate a page for PTE-level kernel
> > page table
> > * @mm: the mm_struct of the current context
>
> ...
>
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index c13c7af7cad3..ab63d5a201cb 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -2327,6 +2327,13 @@ static inline bool ptlock_init(struct page
> > *page) { return true; }
> > static inline void ptlock_free(struct page *page) {}
> > #endif /* USE_SPLIT_PTE_PTLOCKS */
> >
> > +#ifndef CONFIG_PKS_PG_TABLES
> > +static inline void free_table(struct page *table_page)
> > +{
> > + __free_pages(table_page, 0);
> > +}
> > +#endif /* CONFIG_PKS_PG_TABLES */
> > +
>
> Can't this live in asm-generic/pgalloc.h?
> Then you won't need to include linux/mm.h there.
Some architectures couldn't find it in asm-generic/pgalloc.h. There is
some other page table stuff in linux/mm.h so didn't seem too strange.
>
> > static inline void pgtable_init(void)
> > {
> > ptlock_cache_init();
> > @@ -2337,7 +2344,6 @@ static inline bool
> > pgtable_pte_page_ctor(struct page *page)
> > {
> > if (!ptlock_init(page))
> > return false;
> > - __SetPageTable(page);
>
> This change is only valid when __HAVE_ARCH_ALLOC_TABLE is set.
Argh, thanks. Overall solution should still work I think. I'll rework
it to support both.
>
> > inc_lruvec_page_state(page, NR_PAGETABLE);
> > return true;
> > }
> > @@ -2345,7 +2351,6 @@ static inline bool
> > pgtable_pte_page_ctor(struct page *page)
> > static inline void pgtable_pte_page_dtor(struct page *page)
> > {
> > ptlock_free(page);
> > - __ClearPageTable(page);
> > dec_lruvec_page_state(page, NR_PAGETABLE);
> > }
> >
>
>
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