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Mon, 09 Dec 2019 06:11:18 -0500 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AEAE9107ACC4; Mon, 9 Dec 2019 11:11:16 +0000 (UTC) Received: from [10.36.117.245] (ovpn-117-245.ams2.redhat.com [10.36.117.245]) by smtp.corp.redhat.com (Postfix) with ESMTP id 04E0546; Mon, 9 Dec 2019 11:11:14 +0000 (UTC) Subject: Re: [PATCH] mm/hotplug: Only respect mem= parameter during boot stage To: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= , Michal Hocko , Baoquan He Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, william.kucharski@oracle.com, mingo@kernel.org, akpm@linux-foundation.org References: <20191206150524.14687-1-bhe@redhat.com> <20191209100717.GC6156@dhcp22.suse.cz> <7fc610be-df56-c5ae-33fb-53b471aa76d1@suse.com> <94aead35-1541-6c1a-d172-70dc613410c2@redhat.com> <1089517e-4454-be5e-1320-7f246c4efefe@suse.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <1089517e-4454-be5e-1320-7f246c4efefe@suse.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-MC-Unique: mxayHfizP-yZlVUgZXwMiw-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09.12.19 12:08, J=C3=BCrgen Gro=C3=9F wrote: > On 09.12.19 12:01, David Hildenbrand wrote: >> On 09.12.19 11:24, J=C3=BCrgen Gro=C3=9F wrote: >>> On 09.12.19 11:07, Michal Hocko wrote: >>>> On Fri 06-12-19 23:05:24, Baoquan He wrote: >>>>> In commit 357b4da50a62 ("x86: respect memory size limiting via mem=3D >>>>> parameter") a global varialbe global max_mem_size is added to store >>>>> the value which is parsed from 'mem=3D '. This truly stops those >>>>> DIMM from being added into system memory during boot. >>>>> >>>>> However, it also limits the later memory hotplug functionality. Any >>>>> memory board can't be hot added any more if its region is beyond the >>>>> max_mem_size. System will print error like below: >>>>> >>>>> [ 216.387164] acpi PNP0C80:02: add_memory failed >>>>> [ 216.389301] acpi PNP0C80:02: acpi_memory_enable_device() error >>>>> [ 216.392187] acpi PNP0C80:02: Enumeration failure >>>>> >>>>> >From document of 'mem =3D' parameter, it should be a restriction dur= ing >>>>> boot, but not impact the system memory adding/removing after booting. >>>>> >>>>> mem=3Dnn[KMG] [KNL,BOOT] Force usage of a specific amount of = memory >>>>> >>>>> So fix it by also checking if it's during SYSTEM_BOOTING stage when >>>>> restrict memory adding. Otherwise, skip the restriction. >>>> >>>> Could you be more specific about why the boot vs. later hotplug makes >>>> any difference? The documentation is explicit about the boot time but >>>> considering this seems to be like that since ever I strongly suspect >>>> that this is just an omission. >>>> >>>> Btw. how have you tested the situation fixed by 357b4da50a62? >>> >>> I guess he hasn't. >>> >>> The backtrace of the problem at that time was: >>> >>> [ 8321.876844] [] dump_trace+0x59/0x340 >>> [ 8321.882683] [] show_stack_log_lvl+0xea/0x170 >>> [ 8321.889298] [] show_stack+0x21/0x40 >>> [ 8321.895043] [] dump_stack+0x5c/0x7c >>> [ 8321.900779] [] warn_slowpath_common+0x81/0xb0 >>> [ 8321.907482] [] xen_alloc_pte+0x1d4/0x390 >>> [ 8321.913718] [] >>> pmd_populate_kernel.constprop.6+0x40/0x80 >>> [ 8321.921498] [] phys_pmd_init+0x210/0x255 >>> [ 8321.927724] [] phys_pud_init+0x1da/0x247 >>> [ 8321.933951] [] kernel_physical_mapping_init+0xf5/= 0x1d4 >>> [ 8321.941533] [] init_memory_mapping+0x18d/0x380 >>> [ 8321.948341] [] arch_add_memory+0x59/0xf0 >>> [ 8321.954570] [] add_memory_resource+0x8d/0x160 >>> [ 8321.961283] [] add_memory+0x32/0xf0 >>> [ 8321.967025] [] acpi_memory_device_add+0x131/0x2e0 >>> [ 8321.974128] [] acpi_bus_attach+0xe2/0x190 >>> [ 8321.980453] [] acpi_bus_attach+0x5e/0x190 >>> [ 8321.986778] [] acpi_bus_attach+0x5e/0x190 >>> [ 8321.993103] [] acpi_bus_attach+0x5e/0x190 >>> [ 8321.999428] [] acpi_bus_scan+0x37/0x70 >>> [ 8322.005461] [] acpi_scan_init+0x77/0x1b4 >>> [ 8322.011690] [] acpi_init+0x297/0x2b3 >>> [ 8322.017530] [] do_one_initcall+0xca/0x1f0 >>> [ 8322.023855] [] kernel_init_freeable+0x194/0x226 >>> [ 8322.030760] [] kernel_init+0xa/0xe0 >>> [ 8322.036503] [] ret_from_fork+0x55/0x80 >>> >>> So this patch would break it again. >>> >>> I'd recommend ... >>> >>>> >>>>> Fixes: 357b4da50a62 ("x86: respect memory size limiting via mem=3D pa= rameter") >>>>> Signed-off-by: Baoquan He >>>>> --- >>>>> mm/memory_hotplug.c | 2 +- >>>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>>> >>>>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >>>>> index 55ac23ef11c1..5466a0a00901 100644 >>>>> --- a/mm/memory_hotplug.c >>>>> +++ b/mm/memory_hotplug.c >>>>> @@ -105,7 +105,7 @@ static struct resource *register_memory_resource(= u64 start, u64 size) >>>>> =09unsigned long flags =3D IORESOURCE_SYSTEM_RAM | IORESOURCE_BUS= Y; >>>>> =09char *resource_name =3D "System RAM"; >>>>> =20 >>>>> -=09if (start + size > max_mem_size) >>>>> +=09if (start + size > max_mem_size && system_state =3D=3D SYSTEM_BOO= TING) >>> >>> ... changing this to: ... && system_state !=3D SYSTEM_RUNNING >> >> I think we usually use system_state < SYSTEM_RUNNING >> >=20 > Works for me as well. :-) >=20 As this patch has to be resent, I'd also enjoy a comment explaining why this special check is in place /* Make sure memory hotplug works although mem=3D was specified */ or sth. like that :) >=20 > Juergen >=20 --=20 Thanks, David / dhildenb