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=-5.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED 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 C5745C43441 for ; Tue, 27 Nov 2018 03:28:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6F5F620664 for ; Tue, 27 Nov 2018 03:28:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="iD44wv+d" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6F5F620664 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=oracle.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728389AbeK0OZC (ORCPT ); Tue, 27 Nov 2018 09:25:02 -0500 Received: from aserp2120.oracle.com ([141.146.126.78]:38228 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728346AbeK0OZB (ORCPT ); Tue, 27 Nov 2018 09:25:01 -0500 Received: from pps.filterd (aserp2120.oracle.com [127.0.0.1]) by aserp2120.oracle.com (8.16.0.22/8.16.0.22) with SMTP id wAR3OGDv023064; Tue, 27 Nov 2018 03:28:26 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2018-07-02; bh=RFfRhE9xgMtQpr+uaQ0hn/y5rMjhmrtTotR0iMKd88A=; b=iD44wv+d1w8VbQMQNkVvK/npb4OenpdnhAMyNISi1JMBbK8RotpSYn60++bGSApG7oQN zYOxD0imNxZ5ZfVDZj1f4M1+557jOVv1jtmGSs97ENIKwz5Tv3nnAVpt6R1mShxjMq5u JrCqvqRpcgb9wT5Q0q7VwcFZlexAvNucMaItxia1WQcI4ha4smV7TwH1Q96AaX3p8Mjt 0OjVsagJFC3Wqq2C17rAYZ8BKEPC/McYSLRuO2CfQVGLpSjU9m+lqBDM67L3TeYqcKXl V0e0qm+iqu7GjgMFEOXShDQ7LcfuEv/6YPTS88mYI0fe/XWLQHnIN4+2bGeSRoWHcg+0 1Q== Received: from aserv0022.oracle.com (aserv0022.oracle.com [141.146.126.234]) by aserp2120.oracle.com with ESMTP id 2nxxkq9ddn-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 27 Nov 2018 03:28:26 +0000 Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by aserv0022.oracle.com (8.14.4/8.14.4) with ESMTP id wAR3SP2v016092 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 27 Nov 2018 03:28:26 GMT Received: from abhmp0017.oracle.com (abhmp0017.oracle.com [141.146.116.23]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id wAR3SORf023886; Tue, 27 Nov 2018 03:28:24 GMT Received: from dhcp-burlington7-2nd-B-east-10-152-55-162.usdhcp.oraclecorp.com (/10.152.32.65) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 26 Nov 2018 19:28:24 -0800 Subject: Re: [Xen-devel] [PATCH v3] xen/balloon: Mark unallocated host memory as UNUSABLE To: Igor Druzhinin , xen-devel@lists.xen.org, linux-kernel@vger.kernel.org Cc: jgross@suse.com, helgaas@kernel.org, christian.koenig@amd.com, JBeulich@suse.com References: <1513778746-6155-1-git-send-email-boris.ostrovsky@oracle.com> <7c833e3a-4a0b-e80c-91e2-4348d6959651@citrix.com> <3dd5153d-0f17-0e3b-7ebb-5579a7200765@oracle.com> From: Boris Ostrovsky Openpgp: preference=signencrypt Autocrypt: addr=boris.ostrovsky@oracle.com; prefer-encrypt=mutual; keydata= xsFNBFH8CgsBEAC0KiOi9siOvlXatK2xX99e/J3OvApoYWjieVQ9232Eb7GzCWrItCzP8FUV PQg8rMsSd0OzIvvjbEAvaWLlbs8wa3MtVLysHY/DfqRK9Zvr/RgrsYC6ukOB7igy2PGqZd+M MDnSmVzik0sPvB6xPV7QyFsykEgpnHbvdZAUy/vyys8xgT0PVYR5hyvhyf6VIfGuvqIsvJw5 C8+P71CHI+U/IhsKrLrsiYHpAhQkw+Zvyeml6XSi5w4LXDbF+3oholKYCkPwxmGdK8MUIdkM d7iYdKqiP4W6FKQou/lC3jvOceGupEoDV9botSWEIIlKdtm6C4GfL45RD8V4B9iy24JHPlom woVWc0xBZboQguhauQqrBFooHO3roEeM1pxXjLUbDtH4t3SAI3gt4dpSyT3EvzhyNQVVIxj2 FXnIChrYxR6S0ijSqUKO0cAduenhBrpYbz9qFcB/GyxD+ZWY7OgQKHUZMWapx5bHGQ8bUZz2 SfjZwK+GETGhfkvNMf6zXbZkDq4kKB/ywaKvVPodS1Poa44+B9sxbUp1jMfFtlOJ3AYB0WDS Op3d7F2ry20CIf1Ifh0nIxkQPkTX7aX5rI92oZeu5u038dHUu/dO2EcuCjl1eDMGm5PLHDSP 0QUw5xzk1Y8MG1JQ56PtqReO33inBXG63yTIikJmUXFTw6lLJwARAQABzTNCb3JpcyBPc3Ry b3Zza3kgKFdvcmspIDxib3Jpcy5vc3Ryb3Zza3lAb3JhY2xlLmNvbT7CwXgEEwECACIFAlH8 CgsCGwMGCwkIBwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEIredpCGysGyasEP/j5xApopUf4g 9Fl3UxZuBx+oduuw3JHqgbGZ2siA3EA4bKwtKq8eT7ekpApn4c0HA8TWTDtgZtLSV5IdH+9z JimBDrhLkDI3Zsx2CafL4pMJvpUavhc5mEU8myp4dWCuIylHiWG65agvUeFZYK4P33fGqoaS VGx3tsQIAr7MsQxilMfRiTEoYH0WWthhE0YVQzV6kx4wj4yLGYPPBtFqnrapKKC8yFTpgjaK jImqWhU9CSUAXdNEs/oKVR1XlkDpMCFDl88vKAuJwugnixjbPFTVPyoC7+4Bm/FnL3iwlJVE qIGQRspt09r+datFzPqSbp5Fo/9m4JSvgtPp2X2+gIGgLPWp2ft1NXHHVWP19sPgEsEJXSr9 tskM8ScxEkqAUuDs6+x/ISX8wa5Pvmo65drN+JWA8EqKOHQG6LUsUdJolFM2i4Z0k40BnFU/ kjTARjrXW94LwokVy4x+ZYgImrnKWeKac6fMfMwH2aKpCQLlVxdO4qvJkv92SzZz4538az1T m+3ekJAimou89cXwXHCFb5WqJcyjDfdQF857vTn1z4qu7udYCuuV/4xDEhslUq1+GcNDjAhB nNYPzD+SvhWEsrjuXv+fDONdJtmLUpKs4Jtak3smGGhZsqpcNv8nQzUGDQZjuCSmDqW8vn2o hWwveNeRTkxh+2x1Qb3GT46uzsFNBFH8CgsBEADGC/yx5ctcLQlB9hbq7KNqCDyZNoYu1HAB Hal3MuxPfoGKObEktawQPQaSTB5vNlDxKihezLnlT/PKjcXC2R1OjSDinlu5XNGc6mnky03q yymUPyiMtWhBBftezTRxWRslPaFWlg/h/Y1iDuOcklhpr7K1h1jRPCrf1yIoxbIpDbffnuyz kuto4AahRvBU4Js4sU7f/btU+h+e0AcLVzIhTVPIz7PM+Gk2LNzZ3/on4dnEc/qd+ZZFlOQ4 KDN/hPqlwA/YJsKzAPX51L6Vv344pqTm6Z0f9M7YALB/11FO2nBB7zw7HAUYqJeHutCwxm7i BDNt0g9fhviNcJzagqJ1R7aPjtjBoYvKkbwNu5sWDpQ4idnsnck4YT6ctzN4I+6lfkU8zMzC gM2R4qqUXmxFIS4Bee+gnJi0Pc3KcBYBZsDK44FtM//5Cp9DrxRQOh19kNHBlxkmEb8kL/pw XIDcEq8MXzPBbxwHKJ3QRWRe5jPNpf8HCjnZz0XyJV0/4M1JvOua7IZftOttQ6KnM4m6WNIZ 2ydg7dBhDa6iv1oKdL7wdp/rCulVWn8R7+3cRK95SnWiJ0qKDlMbIN8oGMhHdin8cSRYdmHK kTnvSGJNlkis5a+048o0C6jI3LozQYD/W9wq7MvgChgVQw1iEOB4u/3FXDEGulRVko6xCBU4 SQARAQABwsFfBBgBAgAJBQJR/AoLAhsMAAoJEIredpCGysGyfvMQAIywR6jTqix6/fL0Ip8G jpt3uk//QNxGJE3ZkUNLX6N786vnEJvc1beCu6EwqD1ezG9fJKMl7F3SEgpYaiKEcHfoKGdh 30B3Hsq44vOoxR6zxw2B/giADjhmWTP5tWQ9548N4VhIZMYQMQCkdqaueSL+8asp8tBNP+TJ PAIIANYvJaD8xA7sYUXGTzOXDh2THWSvmEWWmzok8er/u6ZKdS1YmZkUy8cfzrll/9hiGCTj u3qcaOM6i/m4hqtvsI1cOORMVwjJF4+IkC5ZBoeRs/xW5zIBdSUoC8L+OCyj5JETWTt40+lu qoqAF/AEGsNZTrwHJYu9rbHH260C0KYCNqmxDdcROUqIzJdzDKOrDmebkEVnxVeLJBIhYZUd t3Iq9hdjpU50TA6sQ3mZxzBdfRgg+vaj2DsJqI5Xla9QGKD+xNT6v14cZuIMZzO7w0DoojM4 ByrabFsOQxGvE0w9Dch2BDSI2Xyk1zjPKxG1VNBQVx3flH37QDWpL2zlJikW29Ws86PHdthh Fm5PY8YtX576DchSP6qJC57/eAAe/9ztZdVAdesQwGb9hZHJc75B+VNm4xrh/PJO6c1THqdQ 19WVJ+7rDx3PhVncGlbAOiiiE3NOFPJ1OQYxPKtpBUukAlOTnkKE6QcA4zckFepUkfmBV1wM Jg6OxFYd01z+a+oL Message-ID: Date: Mon, 26 Nov 2018 22:28:12 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9089 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1811270026 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/26/18 2:57 PM, Igor Druzhinin wrote: > On 26/11/2018 19:42, Boris Ostrovsky wrote: >> On 11/26/18 12:10 PM, Igor Druzhinin wrote: >>> On 26/11/2018 16:25, Boris Ostrovsky wrote: >>>> On 11/25/18 8:00 PM, Igor Druzhinin wrote: >>>>> On 20/12/2017 14:05, Boris Ostrovsky wrote: >>>>>> Commit f5775e0b6116 ("x86/xen: discard RAM regions above the maximum >>>>>> reservation") left host memory not assigned to dom0 as available for >>>>>> memory hotplug. >>>>>> >>>>>> Unfortunately this also meant that those regions could be used by >>>>>> others. Specifically, commit fa564ad96366 ("x86/PCI: Enable a 64bit BAR >>>>>> on AMD Family 15h (Models 00-1f, 30-3f, 60-7f)") may try to map those >>>>>> addresses as MMIO. >>>>>> >>>>>> To prevent this mark unallocated host memory as E820_TYPE_UNUSABLE (thus >>>>>> effectively reverting f5775e0b6116) and keep track of that region as >>>>>> a hostmem resource that can be used for the hotplug. >>>>>> >>>>>> Signed-off-by: Boris Ostrovsky >>>>> This commit breaks Xen balloon memory hotplug for us in Dom0 with >>>>> "hoplug_unpopulated" set to 1. The issue is that the common kernel >>>>> memory onlining procedures require "System RAM" resource to be 1-st >>>>> level. That means by inserting it under "Unusable memory" as the commit >>>>> above does (intentionally or not) we make it 2-nd level and break memory >>>>> onlining. >>>> What do you mean by 1st and 2nd level? >>>> >>> I mean the level of a resource in IOMEM tree (the one that's printed >>> from /proc/iomem). 1-st level means its parent is root and so on. >> Ah, OK. Doesn't >> additional_memory_resource()->insert_resource(iomem_resource) place the >> RAM at 1st level? And if not, can we make it so? >> > That'd mean splitting "Unusable memory" resource. Since it's allocated > from bootmem it has proven to be quite difficult but there are seem to > be special functions available particularly for memory resource > management operations that I've not yet experimented with. So the answer > is probably - maybe yes but not straightforward. > >>>>> There are multiple ways to fix it depending on what was the intention of >>>>> original commit and what exactly it tried to workaround. It seems it >>>>> does several things at once: >>>>> 1) Marks non-Dom0 host memory "Unusable memory" in resource tree. >>>>> 2) Keeps track of all the areas safe for hotplug in Dom0 >>>>> 3) Changes allocation algorithms itself in balloon driver to use those areas >>>> Pretty much. (3) is true in the sense that memory is first allocated >>>> from hostmem_resource (which is non-dom0 RAM). >>>> >>>>> Are all the things above necessary to cover the issue in fa564ad96366 >>>>> ("x86/PCI: Enable a 64bit BAR on AMD Family 15h (Models 00-1f, 30-3f, >>>>> 60-7f)")? >>>> Not anymore, as far as that particular commit is concerned, but that's >>>> because of 03a551734 ("x86/PCI: Move and shrink AMD 64-bit window to >>>> avoid conflict") which was introduced after balloon patch. IIRC there >>>> were some issues with fa564ad96366 unrelated to balloon. >>>> >>> If it's not a problem anymore IIUC, can we revert the change as it still >>> breaks "hotplug_unpopulated=1" for the reasons I described above? >> Since this seems to have broken existing feature this would be an >> option. But before going that route I'd like to see if we can fix the patch. >> >> I have been unable to reproduce your problem. Can you describe what you did? >> > It doesn't happen on all configurations as sometimes the memory is > successfully hotplugged to a hole depending on the size of Dom0 memory. > But we reproduced it quite reliably with small Dom0 sizes like 752MB. > > XenServer is using this feature to hotplug additional memory for grant > table operations so we started a VM and observed a stable hang. > >>>>> Can we remove "Unusable memory" resources as soon as we finished >>>>> booting? Is removing on-demand is preferable over "shoot them all" in >>>>> that case? >>>> The concern is that in principle nothing prevents someone else to do >>>> exact same thing fa564ad96366 did, which is grab something from right >>>> above end of RAM as the kernel sees it. And that can be done at any point. >>>> >>> Nothing prevents - true, but that's plainly wrong from OS point of view >>> to grab physical ranges for something without knowing what's actually >>> behind on that platform. >> I am not sure I agree that this is plainly wrong. If not for BIOS issues >> that 03a551734cf mentions I think what the original implementation of >> fa564ad963 did was perfectly reasonable. Which is why I would prefer to >> keep keep the hostmem resource *if possible*. >> > Exactly, those *are* BIOS issues and are not supposed to be workarounded > by the OS. And as the next commit showed even the workaround didn't > quite helped with it. > > I agree that having hotmem as a precaution is fine but only if there is > a non-cringy way to keep things working with it which I'm not sure does > exist. We have most of the interfaces in the resource framework to do what we want. I put together a semi-working prototype but the tricky part is resource locking --- we need to remove a chunk from hostmem (which will cause hostmem to be resized and possibly split), and insert this chunk to iomem's top level as System RAM, all while holding resource_lock. I haven't been able to come up with an acceptable interface for that. Given that we are actually broken I guess I am OK with reverting the patch, but please make sure this works on AMD boxes (I think family 15h is what needs to be tested). -boris > > Igor > >> -boris >> >> >>> I think we shouldn't consider this as a valid >>> thing to do and don't try to workaround initially incorrect code. >>> >>>> -boris >>>> >>>>> Does it even make sense to remove the 1-st level only restriction in >>>>> kernel/resource.c ? >>>> > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xenproject.org > https://lists.xenproject.org/mailman/listinfo/xen-devel