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[209.132.183.28]) by mx.google.com with ESMTPS id l13si67810qvm.104.2019.01.31.10.37.20 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 31 Jan 2019 10:37:20 -0800 (PST) Received-SPF: pass (google.com: domain of jglisse@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of jglisse@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=jglisse@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8D85489AF1; Thu, 31 Jan 2019 18:37:19 +0000 (UTC) Received: from localhost.localdomain.com (unknown [10.20.6.236]) by smtp.corp.redhat.com (Postfix) with ESMTP id 87A7A18506; Thu, 31 Jan 2019 18:37:18 +0000 (UTC) From: jglisse@redhat.com To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Andrea Arcangeli , Peter Xu , Andrew Morton , Paolo Bonzini , =?utf-8?b?UmFkaW0gS3LEjW3DocWZ?= , kvm@vger.kernel.org Subject: [RFC PATCH 3/4] mm/mmu_notifier: set MMU_NOTIFIER_USE_CHANGE_PTE flag where appropriate Date: Thu, 31 Jan 2019 13:37:05 -0500 Message-Id: <20190131183706.20980-4-jglisse@redhat.com> In-Reply-To: <20190131183706.20980-1-jglisse@redhat.com> References: <20190131183706.20980-1-jglisse@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Thu, 31 Jan 2019 18:37:19 +0000 (UTC) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: X-Virus-Scanned: ClamAV using ClamSMTP From: Jérôme Glisse When notifying change for a range use MMU_NOTIFIER_USE_CHANGE_PTE flag for page table update that use set_pte_at_notify() and where the we are going either from read and write to read only with same pfn or read only to read and write with new pfn. Note that set_pte_at_notify() itself should only be use in rare cases ie we do not want to use it when we are updating a significant range of virtual addresses and thus a significant number of pte. Instead for those cases the event provided to mmu notifer invalidate_range_start() callback should be use for optimization. Signed-off-by: Jérôme Glisse Cc: Andrea Arcangeli Cc: Peter Xu Cc: Andrew Morton Cc: Paolo Bonzini Cc: Radim Krčmář Cc: kvm@vger.kernel.org --- include/linux/mmu_notifier.h | 13 +++++++++++++ mm/ksm.c | 6 ++++-- mm/memory.c | 3 ++- 3 files changed, 19 insertions(+), 3 deletions(-) diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h index d7a35975c2bd..0885bf33dc9c 100644 --- a/include/linux/mmu_notifier.h +++ b/include/linux/mmu_notifier.h @@ -43,6 +43,19 @@ enum mmu_notifier_event { }; #define MMU_NOTIFIER_EVENT_BITS order_base_2(MMU_NOTIFY_EVENT_MAX) +/* + * Set MMU_NOTIFIER_USE_CHANGE_PTE only when the page table it updated with the + * set_pte_at_notify() and when pte is updated from read and write to read only + * with same pfn or from read only to read and write with different pfn. It is + * illegal to set in any other circumstances. + * + * Note that set_pte_at_notify() should not be use outside of the above cases. + * When updating a range in batch (like write protecting a range) it is better + * to rely on invalidate_range_start() and struct mmu_notifier_range to infer + * the kind of update that is happening (as an example you can look at the + * mmu_notifier_range_update_to_read_only() function). + */ +#define MMU_NOTIFIER_USE_CHANGE_PTE (1 << MMU_NOTIFIER_EVENT_BITS) #ifdef CONFIG_MMU_NOTIFIER diff --git a/mm/ksm.c b/mm/ksm.c index 97757c5fa15f..b7fb7b560cc0 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -1051,7 +1051,8 @@ static int write_protect_page(struct vm_area_struct *vma, struct page *page, BUG_ON(PageTransCompound(page)); - mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, vma, mm, + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR | + MMU_NOTIFIER_USE_CHANGE_PTE, vma, mm, pvmw.address, pvmw.address + PAGE_SIZE); mmu_notifier_invalidate_range_start(&range); @@ -1140,7 +1141,8 @@ static int replace_page(struct vm_area_struct *vma, struct page *page, if (!pmd) goto out; - mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, vma, mm, addr, + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR | + MMU_NOTIFIER_USE_CHANGE_PTE, vma, mm, addr, addr + PAGE_SIZE); mmu_notifier_invalidate_range_start(&range); diff --git a/mm/memory.c b/mm/memory.c index a8c6922526f6..daf4b0f92af8 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2275,7 +2275,8 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf) __SetPageUptodate(new_page); - mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, vma, mm, + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR | + MMU_NOTIFIER_USE_CHANGE_PTE, vma, mm, vmf->address & PAGE_MASK, (vmf->address & PAGE_MASK) + PAGE_SIZE); mmu_notifier_invalidate_range_start(&range);