From cd9151e26d31048b2b5e00fd02e110e07d2200c9 Mon Sep 17 00:00:00 2001 From: Stefano Stabellini Date: Sun, 4 Aug 2013 15:39:40 +0100 Subject: xen/balloon: set a mapping for ballooned out pages 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 Reviewed-by: David Vrabel CC: alex@alex.org.uk CC: dcrisan@flexiant.com Signed-off-by: Konrad Rzeszutek Wilk --- drivers/xen/balloon.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 66 insertions(+), 3 deletions(-) (limited to 'drivers/xen/balloon.c') diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c index 2a2ef97697b..a3dc75db135 100644 --- a/drivers/xen/balloon.c +++ b/drivers/xen/balloon.c @@ -38,6 +38,7 @@ #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt +#include #include #include #include @@ -52,6 +53,7 @@ #include #include #include +#include #include #include @@ -90,6 +92,8 @@ 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 DEFINE_PER_CPU(struct page *, balloon_scratch_page); + /* List of ballooned pages, threaded through the mem_map array. */ static LIST_HEAD(ballooned_pages); @@ -412,7 +416,8 @@ 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_cpu_var(balloon_scratch_page)), + PAGE_KERNEL_RO), 0); BUG_ON(ret); } #endif @@ -425,7 +430,8 @@ 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_cpu_var(balloon_scratch_page)))); balloon_append(pfn_to_page(pfn)); } @@ -480,6 +486,18 @@ static void balloon_process(struct work_struct *work) mutex_unlock(&balloon_mutex); } +struct page *get_balloon_scratch_page(void) +{ + struct page *ret = get_cpu_var(balloon_scratch_page); + BUG_ON(ret == NULL); + return ret; +} + +void put_balloon_scratch_page(void) +{ + put_cpu_var(balloon_scratch_page); +} + /* Resets the Xen limit, sets new target, and kicks off processing. */ void balloon_set_new_target(unsigned long target) { @@ -573,13 +591,47 @@ 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: + if (per_cpu(balloon_scratch_page, cpu) != NULL) + break; + per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL); + if (per_cpu(balloon_scratch_page, cpu) == NULL) { + pr_warn("Failed to allocate balloon_scratch_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; + for_each_online_cpu(cpu) + { + per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL); + if (per_cpu(balloon_scratch_page, cpu) == NULL) { + pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu); + return -ENOMEM; + } + } + register_cpu_notifier(&balloon_cpu_notifier); + pr_info("Initialising balloon driver\n"); balloon_stats.current_pages = xen_pv_domain() @@ -616,4 +668,15 @@ static int __init balloon_init(void) subsys_initcall(balloon_init); +static int __init balloon_clear(void) +{ + int cpu; + + for_each_possible_cpu(cpu) + per_cpu(balloon_scratch_page, cpu) = NULL; + + return 0; +} +early_initcall(balloon_clear); + MODULE_LICENSE("GPL"); -- cgit v1.2.3-70-g09d2 From 04660bb5d0e4104e01a8fc34e5d51de1d84c09bf Mon Sep 17 00:00:00 2001 From: Wei Liu Date: Tue, 27 Aug 2013 16:17:25 +0100 Subject: xen/balloon: don't set P2M entry for auto translated guest In commit cd9151e2: xen/balloon: set a mapping for ballooned out pages we have the ballooned out page's mapping set to a scratch page. That commit also sets the P2M entry of ballooned out page to the scratch page's MFN. This is necessary for PV guest but not for HVM guest. On the other hand, setting the P2M entry would trigger BUG_ON in __set_phys_to_machine. The correct thing to do here is to avoid calling __set_phys_to_machine for auto translated guest. Signed-off-by: Wei Liu Cc: Stefano Stabellini Signed-off-by: Konrad Rzeszutek Wilk Acked-by: Stefano Stabellini --- drivers/xen/balloon.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'drivers/xen/balloon.c') diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c index a3dc75db135..3101cf6daf5 100644 --- a/drivers/xen/balloon.c +++ b/drivers/xen/balloon.c @@ -430,8 +430,13 @@ 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, - pfn_to_mfn(page_to_pfn(__get_cpu_var(balloon_scratch_page)))); + if (!xen_feature(XENFEAT_auto_translated_physmap)) { + unsigned long p; + struct page *pg; + pg = __get_cpu_var(balloon_scratch_page); + p = page_to_pfn(pg); + __set_phys_to_machine(pfn, pfn_to_mfn(p)); + } balloon_append(pfn_to_page(pfn)); } -- cgit v1.2.3-70-g09d2