Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751328AbdINGQI (ORCPT ); Thu, 14 Sep 2017 02:16:08 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:6476 "EHLO szxga04-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750770AbdINGQH (ORCPT ); Thu, 14 Sep 2017 02:16:07 -0400 Subject: Re: [PATCH v6 03/11] mm, x86: Add support for eXclusive Page Frame Ownership (XPFO) To: Tycho Andersen References: <20170907173609.22696-1-tycho@docker.com> <20170907173609.22696-4-tycho@docker.com> <302be94d-7e44-001d-286c-2b0cd6098f7b@huawei.com> <20170911145020.fat456njvyagcomu@docker> <57e95ad2-81d8-bf83-3e78-1313daa1bb80@canonical.com> <431e2567-7600-3186-1489-93b855c395bd@huawei.com> <20170912143636.avc3ponnervs43kj@docker> <20170912181303.aqjj5ri3mhscw63t@docker> CC: Juerg Haefliger , , , , Marco Benatto , From: Yisheng Xie Message-ID: <689b2f87-46c5-b4be-67e0-a6639c420191@huawei.com> Date: Thu, 14 Sep 2017 14:15:25 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.1.0 MIME-Version: 1.0 In-Reply-To: <20170912181303.aqjj5ri3mhscw63t@docker> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.29.40] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A090204.59BA1E87.005D,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2014-11-16 11:51:01, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: 9581302fc409cf284ee5665a7bab41c6 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6636 Lines: 175 Hi Tycho, On 2017/9/13 2:13, Tycho Andersen wrote: > Hi Yisheng, > >> On Tue, Sep 12, 2017 at 04:05:22PM +0800, Yisheng Xie wrote: >>> IMO, before a page is allocated, it is in buddy system, which means it is free >>> and no other 'map' on the page except direct map. Then if the page is allocated >>> to user, XPFO should unmap the direct map. otherwise the ret2dir may works at >>> this window before it is freed. Or maybe I'm still missing anything. >> >> I agree that it seems broken. I'm just not sure why the test doesn't >> fail. It's certainly worth understanding. > > Ok, so I think what's going on is that the page *is* mapped and unmapped by the > kernel as Juerg described, but only in certain cases. See prep_new_page(), > which has the following: > > if (!free_pages_prezeroed() && (gfp_flags & __GFP_ZERO)) > for (i = 0; i < (1 << order); i++) > clear_highpage(page + i); > > clear_highpage() maps and unmaps the pages, so that's why xpfo works with this > set. Oh, I really missed this point. For we need zero the memory before user get them. Thanks a lot for figuring out. > > I tried with CONFIG_PAGE_POISONING_ZERO=y and page_poison=y, and the > XPFO_READ_USER test does not fail, i.e. the read succeeds. So, I think we need > to include this zeroing condition in xpfo_alloc_pages(), something like the > patch below. Unfortunately, this fails to boot for me, probably for an > unrelated reason that I'll look into. Yes, seems need to fix in this case, and I also a litter puzzle about why boot fail. Thanks Yisheng Xie > > Thanks a lot! > > Tycho > > >>From bfc21a6438cf8c56741af94cac939f1b0f63752c Mon Sep 17 00:00:00 2001 > From: Tycho Andersen > Date: Tue, 12 Sep 2017 12:06:41 -0600 > Subject: [PATCH] draft of unmapping patch > > Signed-off-by: Tycho Andersen > --- > include/linux/xpfo.h | 5 +++-- > mm/compaction.c | 2 +- > mm/internal.h | 2 +- > mm/page_alloc.c | 10 ++++++---- > mm/xpfo.c | 10 ++++++++-- > 5 files changed, 19 insertions(+), 10 deletions(-) > > diff --git a/include/linux/xpfo.h b/include/linux/xpfo.h > index b24be9ac4a2d..c991bf7f051d 100644 > --- a/include/linux/xpfo.h > +++ b/include/linux/xpfo.h > @@ -29,7 +29,7 @@ void xpfo_flush_kernel_tlb(struct page *page, int order); > > void xpfo_kmap(void *kaddr, struct page *page); > void xpfo_kunmap(void *kaddr, struct page *page); > -void xpfo_alloc_pages(struct page *page, int order, gfp_t gfp); > +void xpfo_alloc_pages(struct page *page, int order, gfp_t gfp, bool will_map); > void xpfo_free_pages(struct page *page, int order); > > bool xpfo_page_is_unmapped(struct page *page); > @@ -49,7 +49,8 @@ void xpfo_temp_unmap(const void *addr, size_t size, void **mapping, > > static inline void xpfo_kmap(void *kaddr, struct page *page) { } > static inline void xpfo_kunmap(void *kaddr, struct page *page) { } > -static inline void xpfo_alloc_pages(struct page *page, int order, gfp_t gfp) { } > +static inline void xpfo_alloc_pages(struct page *page, int order, gfp_t gfp, > + bool will_map) { } > static inline void xpfo_free_pages(struct page *page, int order) { } > > static inline bool xpfo_page_is_unmapped(struct page *page) { return false; } > diff --git a/mm/compaction.c b/mm/compaction.c > index fb548e4c7bd4..9a222258e65c 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -76,7 +76,7 @@ static void map_pages(struct list_head *list) > order = page_private(page); > nr_pages = 1 << order; > > - post_alloc_hook(page, order, __GFP_MOVABLE); > + post_alloc_hook(page, order, __GFP_MOVABLE, false); > if (order) > split_page(page, order); > > diff --git a/mm/internal.h b/mm/internal.h > index 4ef49fc55e58..1a0331ec2b2d 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -165,7 +165,7 @@ extern void __free_pages_bootmem(struct page *page, unsigned long pfn, > unsigned int order); > extern void prep_compound_page(struct page *page, unsigned int order); > extern void post_alloc_hook(struct page *page, unsigned int order, > - gfp_t gfp_flags); > + gfp_t gfp_flags, bool will_map); > extern int user_min_free_kbytes; > > #if defined CONFIG_COMPACTION || defined CONFIG_CMA > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 09fdf1bad21f..f73809847c58 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1750,7 +1750,7 @@ static bool check_new_pages(struct page *page, unsigned int order) > } > > inline void post_alloc_hook(struct page *page, unsigned int order, > - gfp_t gfp_flags) > + gfp_t gfp_flags, bool will_map) > { > set_page_private(page, 0); > set_page_refcounted(page); > @@ -1759,18 +1759,20 @@ inline void post_alloc_hook(struct page *page, unsigned int order, > kernel_map_pages(page, 1 << order, 1); > kernel_poison_pages(page, 1 << order, 1); > kasan_alloc_pages(page, order); > - xpfo_alloc_pages(page, order, gfp_flags); > + xpfo_alloc_pages(page, order, gfp_flags, will_map); > set_page_owner(page, order, gfp_flags); > } > > +extern bool xpfo_test; > static void prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags, > unsigned int alloc_flags) > { > int i; > + bool needs_zero = !free_pages_prezeroed() && (gfp_flags & __GFP_ZERO); > > - post_alloc_hook(page, order, gfp_flags); > + post_alloc_hook(page, order, gfp_flags, needs_zero); > > - if (!free_pages_prezeroed() && (gfp_flags & __GFP_ZERO)) > + if (needs_zero) > for (i = 0; i < (1 << order); i++) > clear_highpage(page + i); > > diff --git a/mm/xpfo.c b/mm/xpfo.c > index ca5d4d1838f9..dd25e24213fe 100644 > --- a/mm/xpfo.c > +++ b/mm/xpfo.c > @@ -86,7 +86,7 @@ static inline struct xpfo *lookup_xpfo(struct page *page) > return (void *)page_ext + page_xpfo_ops.offset; > } > > -void xpfo_alloc_pages(struct page *page, int order, gfp_t gfp) > +void xpfo_alloc_pages(struct page *page, int order, gfp_t gfp, bool will_map) > { > int i, flush_tlb = 0; > struct xpfo *xpfo; > @@ -116,8 +116,14 @@ void xpfo_alloc_pages(struct page *page, int order, gfp_t gfp) > * Tag the page as a user page and flush the TLB if it > * was previously allocated to the kernel. > */ > - if (!test_and_set_bit(XPFO_PAGE_USER, &xpfo->flags)) > + bool was_user = !test_and_set_bit(XPFO_PAGE_USER, > + &xpfo->flags); > + > + if (was_user || !will_map) { > + set_kpte(page_address(page + i), page + i, > + __pgprot(0)); > flush_tlb = 1; > + } > } else { > /* Tag the page as a non-user (kernel) page */ > clear_bit(XPFO_PAGE_USER, &xpfo->flags); >