From 2bad07ce28a0f61c1e776f99aa05f85e4e689e24 Mon Sep 17 00:00:00 2001 From: David Vrabel Date: Wed, 11 Sep 2013 17:45:44 +0000 Subject: xen/balloon: ensure preemption is disabled when using a scratch page In decrease_reservation(), if the kernel is preempted between updating the mapping and updating the p2m then they may end up using different scratch pages. Use get_balloon_scratch_page() and put_balloon_scratch_page() which use get_cpu_var() and put_cpu_var() to correctly disable preemption. Signed-off-by: David Vrabel Signed-off-by: Stefano Stabellini Tested-by: Sander Eikelenboom diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c index 3101cf6..4a43bc3 100644 --- a/drivers/xen/balloon.c +++ b/drivers/xen/balloon.c @@ -380,6 +380,7 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp) enum bp_state state = BP_DONE; unsigned long pfn, i; struct page *page; + struct page *scratch_page; int ret; struct xen_memory_reservation reservation = { .address_bits = 0, @@ -399,6 +400,8 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp) if (nr_pages > ARRAY_SIZE(frame_list)) nr_pages = ARRAY_SIZE(frame_list); + scratch_page = get_balloon_scratch_page(); + for (i = 0; i < nr_pages; i++) { page = alloc_page(gfp); if (page == NULL) { @@ -416,7 +419,7 @@ 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), - pfn_pte(page_to_pfn(__get_cpu_var(balloon_scratch_page)), + pfn_pte(page_to_pfn(scratch_page), PAGE_KERNEL_RO), 0); BUG_ON(ret); } @@ -432,14 +435,14 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp) pfn = mfn_to_pfn(frame_list[i]); 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); + p = page_to_pfn(scratch_page); __set_phys_to_machine(pfn, pfn_to_mfn(p)); } balloon_append(pfn_to_page(pfn)); } + put_balloon_scratch_page(); + set_xen_guest_handle(reservation.extent_start, frame_list); reservation.nr_extents = nr_pages; ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation); -- cgit v0.10.2 From 6a6f6e72eca5ed999689c69d1ac411fe319844a0 Mon Sep 17 00:00:00 2001 From: Wei Liu Date: Wed, 11 Sep 2013 17:54:02 +0000 Subject: xen/balloon: remove BUG_ON in increase_reservation The BUG_ON in increase_reservation is wrong as we have P2M entry ballooned out page set to balloon scratch page, so it might have a valid P2M entry at that point. Signed-off-by: Wei Liu Signed-off-by: Stefano Stabellini diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c index 4a43bc3..a50c6e3 100644 --- a/drivers/xen/balloon.c +++ b/drivers/xen/balloon.c @@ -349,8 +349,6 @@ static enum bp_state increase_reservation(unsigned long nr_pages) BUG_ON(page == NULL); pfn = page_to_pfn(page); - BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) && - phys_to_machine_mapping_valid(pfn)); set_phys_to_machine(pfn, frame_list[i]); -- cgit v0.10.2