From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 11729C43331 for ; Fri, 27 Mar 2020 02:55:11 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B85FB2074D for ; Fri, 27 Mar 2020 02:55:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="QMQh+ypQ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B85FB2074D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 5CFDD6B0010; Thu, 26 Mar 2020 22:55:10 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 57F3C6B0032; Thu, 26 Mar 2020 22:55:10 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 46E0D6B0036; Thu, 26 Mar 2020 22:55:10 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0125.hostedemail.com [216.40.44.125]) by kanga.kvack.org (Postfix) with ESMTP id 2D0246B0010 for ; Thu, 26 Mar 2020 22:55:10 -0400 (EDT) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 114BD5833 for ; Fri, 27 Mar 2020 02:55:10 +0000 (UTC) X-FDA: 76639625580.14.form79_67499666ce601 X-HE-Tag: form79_67499666ce601 X-Filterd-Recvd-Size: 7357 Received: from us-smtp-delivery-74.mimecast.com (us-smtp-delivery-74.mimecast.com [63.128.21.74]) by imf37.hostedemail.com (Postfix) with ESMTP for ; Fri, 27 Mar 2020 02:55:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1585277709; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=RXXhjv8XaV5MoXTlfuTHZa0hm43kWbxrZ9f07+CK+9c=; b=QMQh+ypQKAUprUsu+xrAaFMiN8Tw+kdqHIsHPLI7bVGX50A9CTvdn5MO9gZjrpr7X877a1 wiAtvhf4kUnkxo7zbM0izH2ZzZhQbin2GbDrPV9kFMJnkTXt7SwDK2prchVuqRvfeMtcSO HkYLWdYIDN2ka90fZWRVCtpch5aqh4w= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-366-f_uJsXkmO_i5WLjxFF676A-1; Thu, 26 Mar 2020 22:55:05 -0400 X-MC-Unique: f_uJsXkmO_i5WLjxFF676A-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 977A7800EBD; Fri, 27 Mar 2020 02:55:03 +0000 (UTC) Received: from localhost (ovpn-12-80.pek2.redhat.com [10.72.12.80]) by smtp.corp.redhat.com (Postfix) with ESMTPS id CD4A360C18; Fri, 27 Mar 2020 02:55:02 +0000 (UTC) Date: Fri, 27 Mar 2020 10:54:59 +0800 From: Baoquan He To: Anshuman Khandual Cc: James Morse , kexec@lists.infradead.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, Eric Biederman , Andrew Morton , Catalin Marinas , Will Deacon , Bhupesh Sharma Subject: Re: [PATCH 1/3] kexec: Prevent removal of memory in use by a loaded kexec image Message-ID: <20200327025459.GP3039@MiWiFi-R3L-srv> References: <20200326180730.4754-1-james.morse@arm.com> <20200326180730.4754-2-james.morse@arm.com> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline 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 03/27/20 at 06:13am, Anshuman Khandual wrote: >=20 >=20 > On 03/26/2020 11:37 PM, James Morse wrote: > > An image loaded for kexec is not stored in place, instead its segments > > are scattered through memory, and are re-assembled when needed. In the > > meantime, the target memory may have been removed. > >=20 > > Because mm is not aware that this memory is still in use, it allows it > > to be removed. >=20 > Why the isolation process does not fail when these pages are currently > being used by kexec ? That is trick of kexec implementaiton. When loading kexec-ed kernel, it just reads in the kenrel image in user space, then searches a place where it's going to put kernel image in the whole system RAM, but won't put kernel image in the searched region immediately, just book ahead a room. When you execute 'kexec -e' to trigger kexec jumping, it will copy kernel image into the booked room. So the booking is only recorded in kexec's own data structure. >=20 > >=20 > > Add a memory notifier to prevent the removal of memory regions that > > overlap with a loaded kexec image segment. e.g., when triggered from th= e > > Qemu console: > > | kexec_core: memory region in use > > | memory memory32: Offline failed. >=20 > Yes this is definitely an added protection for these kexec loaded kernels > memory areas from being offlined but I would have expected the preceding > offlining to have failed as well. >=20 > >=20 > > Signed-off-by: James Morse > > --- > > kernel/kexec_core.c | 56 +++++++++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 56 insertions(+) > >=20 > > diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c > > index c19c0dad1ebe..ba1d91e868ca 100644 > > --- a/kernel/kexec_core.c > > +++ b/kernel/kexec_core.c > > @@ -12,6 +12,7 @@ > > #include > > #include > > #include > > +#include > > #include > > #include > > #include > > @@ -22,10 +23,12 @@ > > #include > > #include > > #include > > +#include > > #include > > #include > > #include > > #include > > +#include > > #include > > #include > > #include > > @@ -1219,3 +1222,56 @@ void __weak arch_kexec_protect_crashkres(void) > > =20 > > void __weak arch_kexec_unprotect_crashkres(void) > > {} > > + > > +/* > > + * If user-space wants to offline memory that is in use by a loaded ke= xec > > + * image, it should unload the image first. > > + */ >=20 > Probably this would need kexec user manual and related system call man pa= ges > update as well. >=20 > > +static int mem_remove_cb(struct notifier_block *nb, unsigned long acti= on, > > +=09=09=09 void *data) > > +{ > > +=09int rv =3D NOTIFY_OK, i; > > +=09struct memory_notify *arg =3D data; > > +=09unsigned long pfn =3D arg->start_pfn; > > +=09unsigned long nr_segments, sstart, send; > > +=09unsigned long end_pfn =3D arg->start_pfn + arg->nr_pages; > > + > > +=09might_sleep(); >=20 > Required ? >=20 > > + > > +=09if (action !=3D MEM_GOING_OFFLINE) > > +=09=09return NOTIFY_DONE; > > + > > +=09mutex_lock(&kexec_mutex); > > +=09if (kexec_image) { > > +=09=09nr_segments =3D kexec_image->nr_segments; > > + > > +=09=09for (i =3D 0; i < nr_segments; i++) { > > +=09=09=09sstart =3D PFN_DOWN(kexec_image->segment[i].mem); > > +=09=09=09send =3D PFN_UP(kexec_image->segment[i].mem + > > +=09=09=09=09 kexec_image->segment[i].memsz); > > + > > +=09=09=09if ((pfn <=3D sstart && sstart < end_pfn) || > > +=09=09=09 (pfn <=3D send && send < end_pfn)) { > > +=09=09=09=09pr_warn("Memory region in use\n"); > > +=09=09=09=09rv =3D NOTIFY_BAD; > > +=09=09=09=09break; > > +=09=09=09} > > +=09=09} > > +=09} > > +=09mutex_unlock(&kexec_mutex); > > + > > +=09return rv; >=20 > Variable 'rv' is redundant, should use NOTIFY_[BAD|OK] directly instead. >=20 > > +} > > + > > +static struct notifier_block mem_remove_nb =3D { > > +=09.notifier_call =3D mem_remove_cb, > > +}; > > + > > +static int __init register_mem_remove_cb(void) > > +{ > > +=09if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG)) >=20 > Should not all these new code here be wrapped with CONFIG_MEMORY_HOTREMOV= E > to reduce the scope as well as final code size when the config is disable= d. >=20 > > +=09=09return register_memory_notifier(&mem_remove_nb); > > + > > +=09return 0; > > +} > > +device_initcall(register_mem_remove_cb); > >=20 >=20