From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752880AbbCSSlP (ORCPT ); Thu, 19 Mar 2015 14:41:15 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:51037 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751332AbbCSSlM (ORCPT ); Thu, 19 Mar 2015 14:41:12 -0400 Date: Thu, 19 Mar 2015 19:40:57 +0100 From: Daniel Kiper To: Juergen Gross Cc: linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com, konrad.wilk@oracle.com, david.vrabel@citrix.com, boris.ostrovsky@oracle.com Subject: Re: [PATCH 2/2] xen: before ballooning hotplugged memory, set frames to invalid Message-ID: <20150319184057.GH27971@olila.local.net-space.pl> References: <1426775462-981-1-git-send-email-jgross@suse.com> <1426775462-981-3-git-send-email-jgross@suse.com> <20150319162141.GG27971@olila.local.net-space.pl> <550B05BE.7060102@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <550B05BE.7060102@suse.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: aserv0022.oracle.com [141.146.126.234] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 19, 2015 at 06:22:06PM +0100, Juergen Gross wrote: > On 03/19/2015 05:21 PM, Daniel Kiper wrote: > >On Thu, Mar 19, 2015 at 03:31:02PM +0100, Juergen Gross wrote: > >>Commit 25b884a83d487fd62c3de7ac1ab5549979188482 ("x86/xen: set > >>regions above the end of RAM as 1:1") introduced a regression. > >> > >>To be able to add memory pages which were added via memory hotplug to > >>a pv domain, the pages must be "invalid" instead of "identity" in the > >>p2m list before they can be added. > >> > >>Suggested-by: David Vrabel > >>Signed-off-by: Juergen Gross > >>--- > >> drivers/xen/balloon.c | 13 +++++++++++-- > >> 1 file changed, 11 insertions(+), 2 deletions(-) > >> > >>diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c > >>index 0b52d92..52e331f 100644 > >>--- a/drivers/xen/balloon.c > >>+++ b/drivers/xen/balloon.c > >>@@ -221,15 +221,24 @@ static bool balloon_is_inflated(void) > >> > >> static enum bp_state reserve_additional_memory(long credit) > >> { > >>- int nid, rc; > >>+ int nid, rc = 0; > >> u64 hotplug_start_paddr; > >> unsigned long balloon_hotplug = credit; > >>+ unsigned long pfn; > >> > >> hotplug_start_paddr = PFN_PHYS(SECTION_ALIGN_UP(max_pfn)); > >> balloon_hotplug = round_up(balloon_hotplug, PAGES_PER_SECTION); > >> nid = memory_add_physaddr_to_nid(hotplug_start_paddr); > >> > >>- rc = add_memory(nid, hotplug_start_paddr, balloon_hotplug << PAGE_SHIFT); > >>+ for (pfn = PFN_DOWN(hotplug_start_paddr); > >>+ !rc && pfn < PFN_DOWN(hotplug_start_paddr) + balloon_hotplug; > >>+ pfn++) > >>+ if (!set_phys_to_machine(pfn, INVALID_P2M_ENTRY)) > > > >rc = set_phys_to_machine(pfn, INVALID_P2M_ENTRY)? > > Not really. set_phys_to_machine returns false on failure... > > > > >>+ rc = 1; > > > >I do not think that this stuff is needed for HVM or PVH guests. > > True. > > > > >>+ if (!rc) > >>+ rc = add_memory(nid, hotplug_start_paddr, > >>+ balloon_hotplug << PAGE_SHIFT); > >> > >> if (rc) { > >> pr_warn("Cannot add additional memory (%i)\n", rc); > > > >It will be nice to know what part of infrastructure failed. > >Could you create separate pr_warn() message for set_phys_to_machine()? > > Value 1 for rc is the indicator for that case. Well... Personally I prefer explicit messages telling what happened than something which requires digging in a code to understand a problem. Additionally, I think that we should use negative numbers (as David suggested) to signal an error. Most of kernel stuff work in that way. Daniel