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[209.132.183.28]) by mx.google.com with ESMTPS id r48si10090178qtr.9.2019.02.21.09.44.11 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 21 Feb 2019 09:44:12 -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 1F7CC4E341; Thu, 21 Feb 2019 17:44:11 +0000 (UTC) Received: from redhat.com (unknown [10.20.6.236]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 55BE619C58; Thu, 21 Feb 2019 17:44:03 +0000 (UTC) Date: Thu, 21 Feb 2019 12:44:02 -0500 From: Jerome Glisse To: Peter Xu Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, David Hildenbrand , Hugh Dickins , Maya Gokhale , Pavel Emelyanov , Johannes Weiner , Martin Cracauer , Shaohua Li , Marty McFadden , Andrea Arcangeli , Mike Kravetz , Denis Plotnikov , Mike Rapoport , Mel Gorman , "Kirill A . Shutemov" , "Dr . David Alan Gilbert" Subject: Re: [PATCH v2 12/26] userfaultfd: wp: apply _PAGE_UFFD_WP bit Message-ID: <20190221174401.GL2813@redhat.com> References: <20190212025632.28946-1-peterx@redhat.com> <20190212025632.28946-13-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190212025632.28946-13-peterx@redhat.com> User-Agent: Mutt/1.10.0 (2018-05-17) 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 [10.5.110.38]); Thu, 21 Feb 2019 17:44:11 +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: On Tue, Feb 12, 2019 at 10:56:18AM +0800, Peter Xu wrote: > Firstly, introduce two new flags MM_CP_UFFD_WP[_RESOLVE] for > change_protection() when used with uffd-wp and make sure the two new > flags are exclusively used. Then, > > - For MM_CP_UFFD_WP: apply the _PAGE_UFFD_WP bit and remove _PAGE_RW > when a range of memory is write protected by uffd > > - For MM_CP_UFFD_WP_RESOLVE: remove the _PAGE_UFFD_WP bit and recover > _PAGE_RW when write protection is resolved from userspace > > And use this new interface in mwriteprotect_range() to replace the old > MM_CP_DIRTY_ACCT. > > Do this change for both PTEs and huge PMDs. Then we can start to > identify which PTE/PMD is write protected by general (e.g., COW or soft > dirty tracking), and which is for userfaultfd-wp. > > Since we should keep the _PAGE_UFFD_WP when doing pte_modify(), add it > into _PAGE_CHG_MASK as well. Meanwhile, since we have this new bit, we > can be even more strict when detecting uffd-wp page faults in either > do_wp_page() or wp_huge_pmd(). > > Signed-off-by: Peter Xu Few comments but still: Reviewed-by: Jérôme Glisse > --- > arch/x86/include/asm/pgtable_types.h | 2 +- > include/linux/mm.h | 5 +++++ > mm/huge_memory.c | 14 +++++++++++++- > mm/memory.c | 4 ++-- > mm/mprotect.c | 12 ++++++++++++ > mm/userfaultfd.c | 8 ++++++-- > 6 files changed, 39 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h > index 8cebcff91e57..dd9c6295d610 100644 > --- a/arch/x86/include/asm/pgtable_types.h > +++ b/arch/x86/include/asm/pgtable_types.h > @@ -133,7 +133,7 @@ > */ > #define _PAGE_CHG_MASK (PTE_PFN_MASK | _PAGE_PCD | _PAGE_PWT | \ > _PAGE_SPECIAL | _PAGE_ACCESSED | _PAGE_DIRTY | \ > - _PAGE_SOFT_DIRTY | _PAGE_DEVMAP) > + _PAGE_SOFT_DIRTY | _PAGE_DEVMAP | _PAGE_UFFD_WP) > #define _HPAGE_CHG_MASK (_PAGE_CHG_MASK | _PAGE_PSE) This chunk needs to be in the earlier arch specific patch. [...] > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 8d65b0f041f9..817335b443c2 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c [...] > @@ -2198,6 +2208,8 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > entry = pte_mkold(entry); > if (soft_dirty) > entry = pte_mksoft_dirty(entry); > + if (uffd_wp) > + entry = pte_mkuffd_wp(entry); > } > pte = pte_offset_map(&_pmd, addr); > BUG_ON(!pte_none(*pte)); Reading that code and i thought i would be nice if we could define a pte_mask that we can or instead of all those if () entry |= ... but that is just some dumb optimization and does not have any bearing on the present patch. Just wanted to say that outloud. > diff --git a/mm/mprotect.c b/mm/mprotect.c > index a6ba448c8565..9d4433044c21 100644 > --- a/mm/mprotect.c > +++ b/mm/mprotect.c > @@ -46,6 +46,8 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, > int target_node = NUMA_NO_NODE; > bool dirty_accountable = cp_flags & MM_CP_DIRTY_ACCT; > bool prot_numa = cp_flags & MM_CP_PROT_NUMA; > + bool uffd_wp = cp_flags & MM_CP_UFFD_WP; > + bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE; > > /* > * Can be called with only the mmap_sem for reading by > @@ -117,6 +119,14 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, > if (preserve_write) > ptent = pte_mk_savedwrite(ptent); > > + if (uffd_wp) { > + ptent = pte_wrprotect(ptent); > + ptent = pte_mkuffd_wp(ptent); > + } else if (uffd_wp_resolve) { > + ptent = pte_mkwrite(ptent); > + ptent = pte_clear_uffd_wp(ptent); > + } > + > /* Avoid taking write faults for known dirty pages */ > if (dirty_accountable && pte_dirty(ptent) && > (pte_soft_dirty(ptent) || > @@ -301,6 +311,8 @@ unsigned long change_protection(struct vm_area_struct *vma, unsigned long start, > { > unsigned long pages; > > + BUG_ON((cp_flags & MM_CP_UFFD_WP_ALL) == MM_CP_UFFD_WP_ALL); Don't you want to abort and return here if both flags are set ? [...]