From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefano Stabellini Subject: [PATCH v2 1/2] xen/balloon: set a mapping for ballooned out pages Date: Mon, 22 Jul 2013 17:28:48 +0100 Message-ID: <1374510529-10395-1-git-send-email-stefano.stabellini@eu.citrix.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: xen-devel@lists.xensource.com Cc: Ian.Campbell@citrix.com, Stefano Stabellini , david.vrabel@citrix.com, alex@alex.org.uk, dcrisan@flexiant.com List-Id: xen-devel@lists.xenproject.org Currently ballooned out pages are mapped to 0 and have INVALID_P2M_ENTRY in the p2m. These ballooned out pages are used to map foreign grants by gntdev and blkback (see alloc_xenballooned_pages). Allocate a page per cpu and map all the ballooned out pages to the corresponding mfn. Set the p2m accordingly. This way reading from a ballooned out page won't cause a kernel crash (see http://lists.xen.org/archives/html/xen-devel/2012-12/msg01154.html). Signed-off-by: Stefano Stabellini CC: alex@alex.org.uk CC: dcrisan@flexiant.com --- drivers/xen/balloon.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++-- include/xen/balloon.h | 2 + 2 files changed, 53 insertions(+), 3 deletions(-) diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c index 930fb68..82bdd0c 100644 --- a/drivers/xen/balloon.c +++ b/drivers/xen/balloon.c @@ -36,6 +36,7 @@ * IN THE SOFTWARE. */ +#include #include #include #include @@ -88,6 +89,8 @@ EXPORT_SYMBOL_GPL(balloon_stats); /* We increase/decrease in batches which fit in a page */ static xen_pfn_t frame_list[PAGE_SIZE / sizeof(unsigned long)]; +static struct page** balloon_trade_pages; + #ifdef CONFIG_HIGHMEM #define inc_totalhigh_pages() (totalhigh_pages++) @@ -423,7 +426,8 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp) if (xen_pv_domain() && !PageHighMem(page)) { ret = HYPERVISOR_update_va_mapping( (unsigned long)__va(pfn << PAGE_SHIFT), - __pte_ma(0), 0); + pfn_pte(page_to_pfn(get_balloon_trade_page()), + PAGE_KERNEL_RO), 0); BUG_ON(ret); } #endif @@ -436,7 +440,8 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp) /* No more mappings: invalidate P2M and add to balloon. */ for (i = 0; i < nr_pages; i++) { pfn = mfn_to_pfn(frame_list[i]); - __set_phys_to_machine(pfn, INVALID_P2M_ENTRY); + __set_phys_to_machine(pfn, + pfn_to_mfn(page_to_pfn(get_balloon_trade_page()))); balloon_append(pfn_to_page(pfn)); } @@ -491,6 +496,12 @@ static void balloon_process(struct work_struct *work) mutex_unlock(&balloon_mutex); } +struct page* get_balloon_trade_page(void) +{ + BUG_ON(balloon_trade_pages[smp_processor_id()] == NULL); + return balloon_trade_pages[smp_processor_id()]; +} + /* Resets the Xen limit, sets new target, and kicks off processing. */ void balloon_set_new_target(unsigned long target) { @@ -584,13 +595,50 @@ static void __init balloon_add_region(unsigned long start_pfn, } } +static int __cpuinit balloon_cpu_notify(struct notifier_block *self, + unsigned long action, void *hcpu) +{ + int cpu = (long)hcpu; + switch (action) { + case CPU_UP_PREPARE: + balloon_trade_pages[cpu] = alloc_page(GFP_KERNEL); + if (balloon_trade_pages[cpu] == NULL) { + pr_warn("Failed to allocate balloon_trade_page for cpu %d\n", cpu); + return NOTIFY_BAD; + } + break; + default: + break; + } + return NOTIFY_OK; +} + +static struct notifier_block balloon_cpu_notifier __cpuinitdata = { + .notifier_call = balloon_cpu_notify, +}; + static int __init balloon_init(void) { - int i; + int i, cpu; if (!xen_domain()) return -ENODEV; + balloon_trade_pages = kzalloc(num_possible_cpus() * sizeof(struct page*), + GFP_KERNEL); + if (balloon_trade_pages == NULL) + return -ENOMEM; + + for_each_online_cpu(cpu) + { + balloon_trade_pages[cpu] = alloc_page(GFP_KERNEL); + if (balloon_trade_pages[cpu] == NULL) { + pr_warn("Failed to allocate balloon_trade_page for cpu %d\n", cpu); + return -ENOMEM; + } + } + register_cpu_notifier(&balloon_cpu_notifier); + pr_info("xen/balloon: Initialising balloon driver.\n"); balloon_stats.current_pages = xen_pv_domain() diff --git a/include/xen/balloon.h b/include/xen/balloon.h index cc2e1a7..e94b4aa 100644 --- a/include/xen/balloon.h +++ b/include/xen/balloon.h @@ -29,6 +29,8 @@ int alloc_xenballooned_pages(int nr_pages, struct page **pages, bool highmem); void free_xenballooned_pages(int nr_pages, struct page **pages); +struct page* get_balloon_trade_page(void); + struct device; #ifdef CONFIG_XEN_SELFBALLOONING extern int register_xen_selfballooning(struct device *dev); -- 1.7.2.5