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Tue, 05 Nov 2019 16:03:47 +0000 Received: from pps.filterd (userp3030.oracle.com [127.0.0.1]) by userp3030.oracle.com (8.16.0.27/8.16.0.27) with SMTP id xA5G3VE6028710; Tue, 5 Nov 2019 16:03:47 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userp3030.oracle.com with ESMTP id 2w333vf417-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 05 Nov 2019 16:03:46 +0000 Received: from abhmp0004.oracle.com (abhmp0004.oracle.com [141.146.116.10]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id xA5G3NnY013682; Tue, 5 Nov 2019 16:03:25 GMT Received: from bostrovs-us.us.oracle.com (/10.152.32.65) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 05 Nov 2019 08:03:23 -0800 Subject: Re: [PATCH v1 09/10] mm/memory_hotplug: Don't mark pages PG_reserved when initializing the memmap To: David Hildenbrand , linux-kernel@vger.kernel.org References: <20191024120938.11237-1-david@redhat.com> <20191024120938.11237-10-david@redhat.com> <4b88ebd7-255d-4f02-a347-5a6c0f4f4ac4@oracle.com> From: Boris Ostrovsky Autocrypt: addr=boris.ostrovsky@oracle.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9432 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=846 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1911050132 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9432 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=945 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1911050131 X-Mailman-Approved-At: Wed, 06 Nov 2019 07:24:41 +1100 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-hyperv@vger.kernel.org, Michal Hocko , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , kvm@vger.kernel.org, Pavel Tatashin , KarimAllah Ahmed , Dave Hansen , Alexander Duyck , Michal Hocko , linux-mm@kvack.org, Paul Mackerras , "H. Peter Anvin" , Wanpeng Li , Alexander Duyck , "K. Y. Srinivasan" , Thomas Gleixner , Kees Cook , devel@driverdev.osuosl.org, Stefano Stabellini , Stephen Hemminger , "Aneesh Kumar K.V" , Joerg Roedel , x86@kernel.org, YueHaibing , "Matthew Wilcox \(Oracle\)" , Mike Rapoport , Peter Zijlstra , Ingo Molnar , Vlastimil Babka , Anthony Yznaga , Oscar Salvador , "Isaac J. Manjarres" , Matt Sickler , Juergen Gross , Anshuman Khandual , Haiyang Zhang , Sasha Levin , kvm-ppc@vger.kernel.org, Qian Cai , Alex Williamson , Mike Rapoport , Borislav Petkov , Nicholas Piggin , Andy Lutomirski , xen-devel@lists.xenproject.org, Dan Williams , Vitaly Kuznetsov , Allison Randal , Jim Mattson , Mel Gorman , Cornelia Huck , Pavel Tatashin , Sean Christopherson , Johannes Weiner , Paolo Bonzini , Andrew Morton , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 11/5/19 5:18 AM, David Hildenbrand wrote: > On 04.11.19 23:44, Boris Ostrovsky wrote: >> On 10/24/19 8:09 AM, David Hildenbrand wrote: >>> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c >>> index 4f2e78a5e4db..af69f057913a 100644 >>> --- a/drivers/xen/balloon.c >>> +++ b/drivers/xen/balloon.c >>> @@ -374,6 +374,13 @@ static void xen_online_page(struct page *page, >>> unsigned int order) >>> mutex_lock(&balloon_mutex); >>> for (i = 0; i < size; i++) { >>> p = pfn_to_page(start_pfn + i); >>> + /* >>> + * TODO: The core used to mark the pages reserved. Most >>> probably >>> + * we can stop doing that now. However, especially >>> + * alloc_xenballooned_pages() left PG_reserved set >>> + * on pages that can get mapped to user space. >>> + */ >>> + __SetPageReserved(p); >> >> I suspect this is not needed. Pages can get into balloon either from >> here or from non-hotplug path (e.g. decrease_reservation()) and so when >> we get a page from the balloon we would get a random page that may or >> may not have Reserved bit set. > > Yeah, I also think it is fine. If you agree, I'll drop this hunk and > add details to the patch description. > > Yes, let's do that. Thanks. -boris