From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f200.google.com (mail-io0-f200.google.com [209.85.223.200]) by kanga.kvack.org (Postfix) with ESMTP id A6FA56B0006 for ; Thu, 14 Jun 2018 21:08:12 -0400 (EDT) Received: by mail-io0-f200.google.com with SMTP id s19-v6so6224012iog.0 for ; Thu, 14 Jun 2018 18:08:12 -0700 (PDT) Received: from tyo161.gate.nec.co.jp (tyo161.gate.nec.co.jp. [114.179.232.161]) by mx.google.com with ESMTPS id 11-v6si514937ito.81.2018.06.14.18.08.10 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 14 Jun 2018 18:08:11 -0700 (PDT) From: Naoya Horiguchi Subject: Re: [PATCH v2] x86/e820: put !E820_TYPE_RAM regions into memblock.reserved Date: Fri, 15 Jun 2018 00:58:54 +0000 Message-ID: <20180615005853.GA1196@hori1.linux.bs1.fc.nec.co.jp> References: <20180607065940.GA7334@techadventures.net> <20180607094921.GA8545@techadventures.net> <20180607100256.GA9129@hori1.linux.bs1.fc.nec.co.jp> <20180613054107.GA5329@hori1.linux.bs1.fc.nec.co.jp> <20180613090700.GG13364@dhcp22.suse.cz> <20180614051618.GB17860@hori1.linux.bs1.fc.nec.co.jp> <20180614053859.GA9863@techadventures.net> <20180614063454.GA32419@hori1.linux.bs1.fc.nec.co.jp> <20180614072103.GA10582@techadventures.net> <20180614112437.GA12511@techadventures.net> In-Reply-To: <20180614112437.GA12511@techadventures.net> Content-Language: ja-JP Content-Type: text/plain; charset="iso-2022-jp" Content-ID: <832FF00820ABBF449D3736DB80D8C7A0@gisp.nec.co.jp> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Oscar Salvador Cc: Michal Hocko , "linux-mm@kvack.org" , Pavel Tatashin , Steven Sistare , Daniel Jordan , Matthew Wilcox , "linux-kernel@vger.kernel.org" , Andrew Morton , "mingo@kernel.org" , "dan.j.williams@intel.com" , Huang Ying On Thu, Jun 14, 2018 at 01:24:37PM +0200, Oscar Salvador wrote: > On Thu, Jun 14, 2018 at 09:21:03AM +0200, Oscar Salvador wrote: > > On Thu, Jun 14, 2018 at 06:34:55AM +0000, Naoya Horiguchi wrote: > > > On Thu, Jun 14, 2018 at 07:38:59AM +0200, Oscar Salvador wrote: > > > > On Thu, Jun 14, 2018 at 05:16:18AM +0000, Naoya Horiguchi wrote: > > > ... > > > > >=20 > > > > > My concern is that there are a few E820 memory types rather than > > > > > E820_TYPE_RAM and E820_TYPE_RESERVED, and I'm not sure that putti= ng them > > > > > all into memblock.reserved is really acceptable. > > > >=20 > > > > Hi Naoya, > > > >=20 > > > > Maybe you could just add to memblock.reserved, all unavailable rang= es within > > > > E820_TYPE_RAM. > > > > Actually, in your original patch, you are walking memblock.memory, = which should > > > > only contain E820_TYPE_RAM ranges (talking about x86). > > > >=20 > > > > So I think the below would to the trick as well? > > > >=20 > > > > @@ -1248,6 +1276,7 @@ void __init e820__memblock_setup(void) > > > > { > > > > int i; > > > > u64 end; > > > > + u64 next =3D 0; > > > > =20 > > > > /* > > > > * The bootstrap memblock region count maximum is 128 entri= es > > > > =20 > > > > @@ -1269,6 +1299,14 @@ void __init e820__memblock_setup(void) > > > > =20 > > > > if (entry->type !=3D E820_TYPE_RAM && entry->type != =3D E820_TYPE_RESERVED_KERN) > > > > continue; > > > > > > > > + =20 > > > > + if (entry->type =3D=3D E820_TYPE_RAM) > > > > + if (next < entry->addr) { > > > > + memblock_reserve (next, next + (entry->add= r - next)); > > > > + next =3D end; > > > > + } > > > >=20 > > > > With the above patch, I can no longer see the issues either. > > >=20 > > > I double-checked and this change looks good to me. > > >=20 > > > >=20 > > > > Although, there is a difference between this and your original patc= h. > > > > In your original patch, you are just zeroing the pages, while with = this one (or with your second patch), > > > > we will zero the page in reserve_bootmem_region(), but that functio= n also init > > > > some other fields of the struct page: > > > >=20 > > > > mm_zero_struct_page(page); > > > > set_page_links(page, zone, nid, pfn); > > > > init_page_count(page); > > > > page_mapcount_reset(page); > > > > page_cpupid_reset_last(page); > > > >=20 > > > > So I am not sure we want to bother doing that for pages that are re= ally unreachable. > > >=20 > > > I think that considering that /proc/kpageflags can check them, some d= ata > > > (even if it's trivial) might be better than just zeros. > > >=20 > > > Here's the updated patch. > > > Thanks for the suggestion and testing! > > >=20 > > > --- > > > From: Naoya Horiguchi > > > Date: Thu, 14 Jun 2018 14:44:36 +0900 > > > Subject: [PATCH] x86/e820: put !E820_TYPE_RAM regions into memblock.r= eserved > > >=20 > > > There is a kernel panic that is triggered when reading /proc/kpagefla= gs > > > on the kernel booted with kernel parameter 'memmap=3Dnn[KMG]!ss[KMG]'= : > > >=20 > > > BUG: unable to handle kernel paging request at fffffffffffffffe > > > PGD 9b20e067 P4D 9b20e067 PUD 9b210067 PMD 0 > > > Oops: 0000 [#1] SMP PTI > > > CPU: 2 PID: 1728 Comm: page-types Not tainted 4.17.0-rc6-mm1-v4.17-= rc6-180605-0816-00236-g2dfb086ef02c+ #160 > > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-= 2.fc28 04/01/2014 > > > RIP: 0010:stable_page_flags+0x27/0x3c0 > > > Code: 00 00 00 0f 1f 44 00 00 48 85 ff 0f 84 a0 03 00 00 41 54 55 4= 9 89 fc 53 48 8b 57 08 48 8b 2f 48 8d 42 ff 83 e2 01 48 0f 44 c7 <48> 8b 00= f6 c4 01 0f 84 10 03 00 00 31 db 49 8b 54 24 08 4c 89 e7 > > > RSP: 0018:ffffbbd44111fde0 EFLAGS: 00010202 > > > RAX: fffffffffffffffe RBX: 00007fffffffeff9 RCX: 0000000000000000 > > > RDX: 0000000000000001 RSI: 0000000000000202 RDI: ffffed1182fff5c0 > > > RBP: ffffffffffffffff R08: 0000000000000001 R09: 0000000000000001 > > > R10: ffffbbd44111fed8 R11: 0000000000000000 R12: ffffed1182fff5c0 > > > R13: 00000000000bffd7 R14: 0000000002fff5c0 R15: ffffbbd44111ff10 > > > FS: 00007efc4335a500(0000) GS:ffff93a5bfc00000(0000) knlGS:0000000= 000000000 > > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > > CR2: fffffffffffffffe CR3: 00000000b2a58000 CR4: 00000000001406e0 > > > Call Trace: > > > kpageflags_read+0xc7/0x120 > > > proc_reg_read+0x3c/0x60 > > > __vfs_read+0x36/0x170 > > > vfs_read+0x89/0x130 > > > ksys_pread64+0x71/0x90 > > > do_syscall_64+0x5b/0x160 > > > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > > RIP: 0033:0x7efc42e75e23 > > > Code: 09 00 ba 9f 01 00 00 e8 ab 81 f4 ff 66 2e 0f 1f 84 00 00 00 0= 0 00 90 83 3d 29 0a 2d 00 00 75 13 49 89 ca b8 11 00 00 00 0f 05 <48> 3d 01= f0 ff ff 73 34 c3 48 83 ec 08 e8 db d3 01 00 48 89 04 24 > > >=20 > > > According to kernel bisection, this problem became visible due to com= mit > > > f7f99100d8d9 which changes how struct pages are initialized. > > >=20 > > > Memblock layout affects the pfn ranges covered by node/zone. Consider > > > that we have a VM with 2 NUMA nodes and each node has 4GB memory, and > > > the default (no memmap=3D given) memblock layout is like below: > > >=20 > > > MEMBLOCK configuration: > > > memory size =3D 0x00000001fff75c00 reserved size =3D 0x00000000030= 0c000 > > > memory.cnt =3D 0x4 > > > memory[0x0] [0x0000000000001000-0x000000000009efff], 0x0000000= 00009e000 bytes on node 0 flags: 0x0 > > > memory[0x1] [0x0000000000100000-0x00000000bffd6fff], 0x0000000= 0bfed7000 bytes on node 0 flags: 0x0 > > > memory[0x2] [0x0000000100000000-0x000000013fffffff], 0x0000000= 040000000 bytes on node 0 flags: 0x0 > > > memory[0x3] [0x0000000140000000-0x000000023fffffff], 0x0000000= 100000000 bytes on node 1 flags: 0x0 > > > ... > > >=20 > > > If you give memmap=3D1G!4G (so it just covers memory[0x2]), > > > the range [0x100000000-0x13fffffff] is gone: > > >=20 > > > MEMBLOCK configuration: > > > memory size =3D 0x00000001bff75c00 reserved size =3D 0x00000000030= 0c000 > > > memory.cnt =3D 0x3 > > > memory[0x0] [0x0000000000001000-0x000000000009efff], 0x0000000= 00009e000 bytes on node 0 flags: 0x0 > > > memory[0x1] [0x0000000000100000-0x00000000bffd6fff], 0x0000000= 0bfed7000 bytes on node 0 flags: 0x0 > > > memory[0x2] [0x0000000140000000-0x000000023fffffff], 0x0000000= 100000000 bytes on node 1 flags: 0x0 > > > ... > > >=20 > > > This causes shrinking node 0's pfn range because it is calculated by > > > the address range of memblock.memory. So some of struct pages in the > > > gap range are left uninitialized. > > >=20 > > > We have a function zero_resv_unavail() which does zeroing the struct > > > pages within the reserved unavailable range (i.e. memblock.memory && > > > !memblock.reserved). This patch utilizes it to cover all unavailable > > > ranges by putting them into memblock.reserved. >=20 > I just spotted this. > It seems that the changelog has not been updated. > It still refers to zero_resv_unavail(), while this patch takes > a different approach. Actually I updated this paragraph a little. v1 changes zero_resv_unavail() itself to do zeroing every range outside memblock.memory!. And v2 keeps zero_resv_unavail() as is, but by newly putting some ranges into memblock.reserved, the ranges become to be handled by zero_resv_unavai= l(), so I still mention this function. It seems that with current patch we zero twice in zero_resv_unavail() and reserve_bootmem_region(), so there might be a room of improvement to remove the duplicate. Thanks, Naoya Horiguchi >=20 > > >=20 > > > Fixes: f7f99100d8d9 ("mm: stop zeroing memory during allocation in vm= emmap") > > > Signed-off-by: Naoya Horiguchi > > > Suggested-by: Oscar Salvador > > > Tested-by: Oscar Salvador > > > --- > > > arch/x86/kernel/e820.c | 12 ++++++++++++ > > > 1 file changed, 12 insertions(+) > > >=20 > > > diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c > > > index d1f25c831447..d15ef47ea354 100644 > > > --- a/arch/x86/kernel/e820.c > > > +++ b/arch/x86/kernel/e820.c > > > @@ -1248,6 +1248,7 @@ void __init e820__memblock_setup(void) > > > { > > > int i; > > > u64 end; > > > + u64 next =3D 0; > > > =20 > > > /* > > > * The bootstrap memblock region count maximum is 128 entries > > > @@ -1270,6 +1271,17 @@ void __init e820__memblock_setup(void) > > > if (entry->type !=3D E820_TYPE_RAM && entry->type !=3D E820_TYPE_R= ESERVED_KERN) > > > continue; > > > =20 > > > + /* > > > + * Ranges unavailable in E820_TYPE_RAM are put into > > > + * memblock.reserved, to make sure that struct pages in such > > > + * regions are not left uninitialized after bootup. > > > + */ > > > + if (entry->type =3D=3D E820_TYPE_RAM) > > > + if (next < entry->addr) { > > > + memblock_reserve (next, next + (entry->addr - next)); > > > + next =3D end; > > > + } > > > + > > > memblock_add(entry->addr, entry->size); > > > } > >=20 > > Thanks Naoya! > >=20 > > Andrew: In case you consider to take this patch instead of the first on= e, > > could you please replace "osalvador@techadventures.net" with "osalvador= @suse.de"? > >=20 > > Thanks > >=20 > > Best Regards > > Oscar Salvador > >=20 >=20 > Best Regards > Oscar Salvador > =