From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935488Ab0GPCMx (ORCPT ); Thu, 15 Jul 2010 22:12:53 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:60976 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S935476Ab0GPCMu (ORCPT ); Thu, 15 Jul 2010 22:12:50 -0400 Message-ID: <4C3FC03A.9040504@cn.fujitsu.com> Date: Fri, 16 Jul 2010 10:13:14 +0800 From: Lai Jiangshan User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.9) Gecko/20100423 Thunderbird/3.0.4 MIME-Version: 1.0 To: LKML , kvm@vger.kernel.org, Avi Kivity , Marcelo Tosatti , Nick Piggin Subject: [PATCH 6/6] kvm, faster and simpler version of get_user_page_and_protection() Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org a light weight version of get_user_page_and_protection() Signed-off-by: Lai Jiangshan --- diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index a34c785..d0e4f2f 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -618,6 +618,8 @@ static inline void clone_pgd_range(pgd_t *dst, pgd_t *src, int count) memcpy(dst, src, count * sizeof(pgd_t)); } +extern +struct page *get_user_page_and_protection(unsigned long addr, int *writable); #include #endif /* __ASSEMBLY__ */ diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 6382140..de44847 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -1832,23 +1832,6 @@ static void kvm_unsync_pages(struct kvm_vcpu *vcpu, gfn_t gfn) } } -/* get a current mapped page fast, and test whether the page is writable. */ -static struct page *get_user_page_and_protection(unsigned long addr, - int *writable) -{ - struct page *page[1]; - - if (__get_user_pages_fast(addr, 1, 1, page) == 1) { - *writable = 1; - return page[0]; - } - if (__get_user_pages_fast(addr, 1, 0, page) == 1) { - *writable = 0; - return page[0]; - } - return NULL; -} - static pfn_t kvm_get_pfn_for_page_fault(struct kvm *kvm, gfn_t gfn, int write_fault, int *host_writable) { diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c index a4ce19f..34b05c7 100644 --- a/arch/x86/mm/gup.c +++ b/arch/x86/mm/gup.c @@ -275,7 +275,6 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, return nr; } -EXPORT_SYMBOL_GPL(__get_user_pages_fast); /** * get_user_pages_fast() - pin user pages in memory @@ -375,3 +374,83 @@ slow_irqon: return ret; } } + +/* + * get a current mapped page fast, and test whether the page is writable. + * equivalent version(but slower): + * { + * struct page *page[1]; + * + * if (__get_user_pages_fast(addr, 1, 1, page) == 1) { + * *writable = 1; + * return page[0]; + * } + * if (__get_user_pages_fast(addr, 1, 0, page) == 1) { + * *writable = 0; + * return page[0]; + * } + * return NULL; + * } + */ +struct page *get_user_page_and_protection(unsigned long addr, int *writable) +{ + unsigned long flags; + struct mm_struct *mm = current->mm; + pgd_t *pgdp; + pud_t *pudp; + pmd_t *pmdp; + pte_t pte, *ptep; + + unsigned long mask = _PAGE_PRESENT | _PAGE_USER; + unsigned long offset = 0; + struct page *head, *page = NULL; + + addr &= PAGE_MASK; + + local_irq_save(flags); + pgdp = pgd_offset(mm, addr); + if (!pgd_present(*pgdp)) + goto out; + + pudp = pud_offset(pgdp, addr); + if (!pud_present(*pudp)) + goto out; + + if (unlikely(pud_large(*pudp))) { + pte = *(pte_t *)pudp; + offset = ((addr & ~PUD_MASK) >> PAGE_SHIFT); + goto verify; + } + + pmdp = pmd_offset(pudp, addr); + if (!pmd_present(*pmdp)) + goto out; + + if (unlikely(pmd_large(*pmdp))) { + pte = *(pte_t *)pmdp; + offset = ((addr & ~PMD_MASK) >> PAGE_SHIFT); + goto verify; + } + + ptep = pte_offset_map(pmdp, addr); + pte = gup_get_pte(ptep); + pte_unmap(ptep); + +verify: + if ((pte_flags(pte) & (mask | _PAGE_SPECIAL)) != mask) + goto out; + + VM_BUG_ON(!pfn_valid(pte_pfn(pte))); + + head = pte_page(pte); + page = head + offset; + VM_BUG_ON(compound_head(page) != head); + get_page(page); + *writable = !!(pte_flags(pte) & _PAGE_RW); + +out: + local_irq_restore(flags); + return page; +} +EXPORT_SYMBOL_GPL(get_user_page_and_protection); +