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Mon, 11 May 2020 23:32:14 +0000 Received: from pps.filterd (userp3030.oracle.com [127.0.0.1]) by userp3030.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 04BNNu4b005736; Mon, 11 May 2020 23:29:56 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userp3030.oracle.com with ESMTP id 30ydsp8634-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 11 May 2020 23:29:56 +0000 Received: from abhmp0012.oracle.com (abhmp0012.oracle.com [141.146.116.18]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 04BNTbb3004361; Mon, 11 May 2020 23:29:37 GMT Received: from [10.154.189.6] (/10.154.189.6) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 11 May 2020 16:29:37 -0700 Subject: Re: [RFC 14/43] mm: memblock: PKRAM: prevent memblock resize from clobbering preserved pages To: Mike Rapoport Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, willy@infradead.org, corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, akpm@linux-foundation.org, hughd@google.com, ebiederm@xmission.com, masahiroy@kernel.org, ardb@kernel.org, ndesaulniers@google.com, dima@golovin.in, daniel.kiper@oracle.com, nivedita@alum.mit.edu, rafael.j.wysocki@intel.com, dan.j.williams@intel.com, zhenzhong.duan@oracle.com, jroedel@suse.de, bhe@redhat.com, guro@fb.com, Thomas.Lendacky@amd.com, andriy.shevchenko@linux.intel.com, keescook@chromium.org, hannes@cmpxchg.org, minchan@kernel.org, mhocko@kernel.org, ying.huang@intel.com, yang.shi@linux.alibaba.com, gustavo@embeddedor.com, ziqian.lzq@antfin.com, vdavydov.dev@gmail.com, jason.zeng@intel.com, kevin.tian@intel.com, zhiyuan.lv@intel.com, lei.l.li@intel.com, paul.c.lai@intel.com, ashok.raj@intel.com, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, kexec@lists.infradead.org References: <1588812129-8596-1-git-send-email-anthony.yznaga@oracle.com> <1588812129-8596-15-git-send-email-anthony.yznaga@oracle.com> <20200511135727.GA983798@linux.ibm.com> From: Anthony Yznaga Organization: Oracle Corporation Message-ID: <54773d69-1a2b-1ab3-24d9-b322d580fb42@oracle.com> Date: Mon, 11 May 2020 16:29:33 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200511135727.GA983798@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9618 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 phishscore=0 suspectscore=2 mlxscore=0 adultscore=0 mlxlogscore=999 malwarescore=0 bulkscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2005110172 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9618 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 impostorscore=0 mlxscore=0 suspectscore=2 bulkscore=0 mlxlogscore=999 phishscore=0 malwarescore=0 lowpriorityscore=0 spamscore=0 adultscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2005110173 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/11/20 6:57 AM, Mike Rapoport wrote: > On Wed, May 06, 2020 at 05:41:40PM -0700, Anthony Yznaga wrote: >> The size of the memblock reserved array may be increased while preserved >> pages are being reserved. When this happens, preserved pages that have >> not yet been reserved are at risk for being clobbered when space for a >> larger array is allocated. >> When called from memblock_double_array(), a wrapper around >> memblock_find_in_range() walks the preserved pages pagetable to find >> sufficiently sized ranges without preserved pages and passes them to >> memblock_find_in_range(). > I'd suggest to create an array of memblock_region's that will contain > the PKRAM ranges before kexec and pass this array to the new kernel. > Then, somewhere in start_kerenel() replace replace > memblock.reserved->regions with that array. I'll look into doing this.  Thanks! Anthony > >> Signed-off-by: Anthony Yznaga >> --- >> include/linux/pkram.h | 3 +++ >> mm/memblock.c | 15 +++++++++++++-- >> mm/pkram.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++ >> 3 files changed, 67 insertions(+), 2 deletions(-) >> >> diff --git a/include/linux/pkram.h b/include/linux/pkram.h >> index edc5d8bef9d3..409022e1472f 100644 >> --- a/include/linux/pkram.h >> +++ b/include/linux/pkram.h >> @@ -62,6 +62,9 @@ struct page *pkram_load_page(struct pkram_stream *ps, unsigned long *index, >> ssize_t pkram_write(struct pkram_stream *ps, const void *buf, size_t count); >> size_t pkram_read(struct pkram_stream *ps, void *buf, size_t count); >> >> +phys_addr_t pkram_memblock_find_in_range(phys_addr_t start, phys_addr_t end, >> + phys_addr_t size, phys_addr_t align); >> + >> #ifdef CONFIG_PKRAM >> extern unsigned long pkram_reserved_pages; >> void pkram_reserve(void); >> diff --git a/mm/memblock.c b/mm/memblock.c >> index c79ba6f9920c..69ae883b8d21 100644 >> --- a/mm/memblock.c >> +++ b/mm/memblock.c >> @@ -16,6 +16,7 @@ >> #include >> #include >> #include >> +#include >> >> #include >> #include >> @@ -349,6 +350,16 @@ phys_addr_t __init_memblock memblock_find_in_range(phys_addr_t start, >> return ret; >> } >> >> +phys_addr_t __init_memblock __memblock_find_in_range(phys_addr_t start, >> + phys_addr_t end, phys_addr_t size, >> + phys_addr_t align) >> +{ >> + if (IS_ENABLED(CONFIG_PKRAM)) >> + return pkram_memblock_find_in_range(start, end, size, align); >> + else >> + return memblock_find_in_range(start, end, size, align); >> +} >> + >> static void __init_memblock memblock_remove_region(struct memblock_type *type, unsigned long r) >> { >> type->total_size -= type->regions[r].size; >> @@ -447,11 +458,11 @@ static int __init_memblock memblock_double_array(struct memblock_type *type, >> if (type != &memblock.reserved) >> new_area_start = new_area_size = 0; >> >> - addr = memblock_find_in_range(new_area_start + new_area_size, >> + addr = __memblock_find_in_range(new_area_start + new_area_size, >> memblock.current_limit, >> new_alloc_size, PAGE_SIZE); >> if (!addr && new_area_size) >> - addr = memblock_find_in_range(0, >> + addr = __memblock_find_in_range(0, >> min(new_area_start, memblock.current_limit), >> new_alloc_size, PAGE_SIZE); >> >> diff --git a/mm/pkram.c b/mm/pkram.c >> index dd3c89614010..e49c9bcd3854 100644 >> --- a/mm/pkram.c >> +++ b/mm/pkram.c >> @@ -1238,3 +1238,54 @@ void pkram_free_pgt(void) >> __free_pages_core(virt_to_page(pkram_pgd), 0); >> pkram_pgd = NULL; >> } >> + >> +static int __init_memblock pkram_memblock_find_cb(struct pkram_pg_state *st, unsigned long base, unsigned long size) >> +{ >> + unsigned long end = base + size; >> + unsigned long addr; >> + >> + if (size < st->min_size) >> + return 0; >> + >> + addr = memblock_find_in_range(base, end, st->min_size, PAGE_SIZE); >> + if (!addr) >> + return 0; >> + >> + st->retval = addr; >> + return 1; >> +} >> + >> +/* >> + * It may be necessary to allocate a larger reserved memblock array >> + * while populating it with ranges of preserved pages. To avoid >> + * trampling preserved pages that have not yet been added to the >> + * memblock reserved list this function implements a wrapper around >> + * memblock_find_in_range() that restricts searches to subranges >> + * that do not contain preserved pages. >> + */ >> +phys_addr_t __init_memblock pkram_memblock_find_in_range(phys_addr_t start, >> + phys_addr_t end, phys_addr_t size, >> + phys_addr_t align) >> +{ >> + struct pkram_pg_state st = { >> + .range_cb = pkram_memblock_find_cb, >> + .min_addr = start, >> + .max_addr = end, >> + .min_size = PAGE_ALIGN(size), >> + .find_holes = true, >> + }; >> + >> + if (!pkram_reservation_in_progress) >> + return memblock_find_in_range(start, end, size, align); >> + >> + if (!pkram_pgd) { >> + WARN_ONCE(1, "No preserved pages pagetable\n"); >> + return memblock_find_in_range(start, end, size, align); >> + } >> + >> + WARN_ONCE(memblock_bottom_up(), "PKRAM: bottom up memblock allocation not yet supported\n"); >> + >> + pkram_walk_pgt_rev(&st, pkram_pgd); >> + >> + return st.retval; >> +} >> -- >> 2.13.3 >>