From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752140AbdGRQH2 (ORCPT ); Tue, 18 Jul 2017 12:07:28 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:40895 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751427AbdGRQHX (ORCPT ); Tue, 18 Jul 2017 12:07:23 -0400 Subject: Re: [PATCH v3] xen/balloon: don't online new memory initially To: Juergen Gross , linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org References: <20170710081045.874-1-jgross@suse.com> From: Boris Ostrovsky Message-ID: <3d195aea-55b7-c412-afbf-534fd143e578@oracle.com> Date: Tue, 18 Jul 2017 12:08:25 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <20170710081045.874-1-jgross@suse.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Source-IP: userv0021.oracle.com [156.151.31.71] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/10/2017 04:10 AM, Juergen Gross wrote: > When setting up the Xenstore watch for the memory target size the new > watch will fire at once. Don't try to reach the configured target size > by onlining new memory in this case, as the current memory size will > be smaller in almost all cases due to e.g. BIOS reserved pages. > > Onlining new memory will lead to more problems e.g. undesired conflicts > with NVMe devices meant to be operated as block devices. > > Instead remember the difference between target size and current size > when the watch fires for the first time and apply it to any further > size changes, too. I don't think I understand how deferring setting the target until next watch firing will help with the original problem. Could you explain? Thanks. -boris > > In order to avoid races between balloon.c and xen-balloon.c init calls > do the xen-balloon.c initialization from balloon.c. > > Signed-off-by: Juergen Gross > --- > drivers/xen/balloon.c | 3 +++ > drivers/xen/xen-balloon.c | 22 ++++++++++++---------- > include/xen/balloon.h | 8 ++++++++ > 3 files changed, 23 insertions(+), 10 deletions(-) > > diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c > index 50dcb68d8070..ab609255a0f3 100644 > --- a/drivers/xen/balloon.c > +++ b/drivers/xen/balloon.c > @@ -780,6 +780,9 @@ static int __init balloon_init(void) > } > #endif > > + /* Init the xen-balloon driver. */ > + xen_balloon_init(); > + > return 0; > } > subsys_initcall(balloon_init); > diff --git a/drivers/xen/xen-balloon.c b/drivers/xen/xen-balloon.c > index e7715cb62eef..e89136ab851e 100644 > --- a/drivers/xen/xen-balloon.c > +++ b/drivers/xen/xen-balloon.c > @@ -59,6 +59,8 @@ static void watch_target(struct xenbus_watch *watch, > { > unsigned long long new_target; > int err; > + static bool watch_fired; > + static long target_diff; > > err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target); > if (err != 1) { > @@ -69,7 +71,14 @@ static void watch_target(struct xenbus_watch *watch, > /* The given memory/target value is in KiB, so it needs converting to > * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10. > */ > - balloon_set_new_target(new_target >> (PAGE_SHIFT - 10)); > + new_target >>= PAGE_SHIFT - 10; > + if (watch_fired) { > + balloon_set_new_target(new_target - target_diff); > + return; > + } > + > + watch_fired = true; > + target_diff = new_target - balloon_stats.target_pages; > } > static struct xenbus_watch target_watch = { > .node = "memory/target", > @@ -94,22 +103,15 @@ static struct notifier_block xenstore_notifier = { > .notifier_call = balloon_init_watcher, > }; > > -static int __init balloon_init(void) > +void xen_balloon_init(void) > { > - if (!xen_domain()) > - return -ENODEV; > - > - pr_info("Initialising balloon driver\n"); > - > register_balloon(&balloon_dev); > > register_xen_selfballooning(&balloon_dev); > > register_xenstore_notifier(&xenstore_notifier); > - > - return 0; > } > -subsys_initcall(balloon_init); > +EXPORT_SYMBOL_GPL(xen_balloon_init); > > #define BALLOON_SHOW(name, format, args...) \ > static ssize_t show_##name(struct device *dev, \ > diff --git a/include/xen/balloon.h b/include/xen/balloon.h > index d1767dfb0d95..8906361bb50c 100644 > --- a/include/xen/balloon.h > +++ b/include/xen/balloon.h > @@ -35,3 +35,11 @@ static inline int register_xen_selfballooning(struct device *dev) > return -ENOSYS; > } > #endif > + > +#ifdef CONFIG_XEN_BALLOON > +void xen_balloon_init(void); > +#else > +static inline void xen_balloon_init(void) > +{ > +} > +#endif