From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752418AbbCWLrv (ORCPT ); Mon, 23 Mar 2015 07:47:51 -0400 Received: from smtp02.citrix.com ([66.165.176.63]:38599 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752290AbbCWLru (ORCPT ); Mon, 23 Mar 2015 07:47:50 -0400 X-IronPort-AV: E=Sophos;i="5.11,452,1422921600"; d="scan'208";a="247420032" Message-ID: <550FFD62.6010004@citrix.com> Date: Mon, 23 Mar 2015 11:47:46 +0000 From: David Vrabel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.4.0 MIME-Version: 1.0 To: Boris Ostrovsky , Juergen Gross , , , , , , Subject: Re: [Xen-devel] [Patch V2 2/2] xen: before ballooning hotplugged memory, set frames to invalid References: <1426856139-3359-1-git-send-email-jgross@suse.com> <1426856139-3359-3-git-send-email-jgross@suse.com> <550C2422.6060409@oracle.com> In-Reply-To: <550C2422.6060409@oracle.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-DLP: MIA1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 20/03/15 13:44, Boris Ostrovsky wrote: > On 03/20/2015 08:55 AM, 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, 13 insertions(+) >> >> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c >> index 0b52d92..65fedb8 100644 >> --- a/drivers/xen/balloon.c >> +++ b/drivers/xen/balloon.c >> @@ -229,6 +229,19 @@ static enum bp_state >> reserve_additional_memory(long credit) >> balloon_hotplug = round_up(balloon_hotplug, PAGES_PER_SECTION); >> nid = memory_add_physaddr_to_nid(hotplug_start_paddr); >> +#ifdef CONFIG_XEN_HAVE_PVMMU I've added this comment: /* * add_memory() will build page tables for the new memory so * the p2m must contain invalidate entries so the correct * non-present PTEs will be written. * * If a failure occurs, the original (identity) p2m entries * are not restored since this region is now known not to * conflict with any devices. */ >> + if (!xen_feature(XENFEAT_auto_translated_physmap)) { >> + unsigned long pfn, i; >> + >> + pfn = PFN_DOWN(hotplug_start_paddr); >> + for (i = 0; i < balloon_hotplug; i++) >> + if (!set_phys_to_machine(pfn + i, INVALID_P2M_ENTRY)) { >> + pr_warn("set_phys_to_machine() failed, no memory >> added\n"); >> + return BP_ECANCELED; > > I should have asked last time --- should we restore [0..i-1] mapping > back to identity on error here? I wonder whether leaving those frames as > invalid (when they are expected to be 'identity') could cause problems > in the future. See new comment above. David