From 60901df3aed230d4565dca003f11b6a95fbf30d9 Mon Sep 17 00:00:00 2001 From: Ross Lagerwall Date: Thu, 17 Mar 2016 16:51:59 +0000 Subject: [PATCH 1/3] xen: Fix page <-> pfn conversion on 32 bit systems Commit 1084b1988d22dc165c9dbbc2b0e057f9248ac4db (xen: Add Xen specific page definition) caused a regression in 4.4. The xen functions to convert between pages and pfns fail due to an overflow on systems where a physical address may not fit in an unsigned long (e.g. x86 32 bit PAE systems). Rework the conversion to avoid overflow. This should also result in simpler object code. This bug manifested itself as disk corruption with Linux 4.4 when using blkfront in a Xen HVM x86 32 bit guest with more than 4 GiB of memory. Signed-off-by: Ross Lagerwall Cc: # 4.4+ Signed-off-by: David Vrabel --- include/xen/page.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/xen/page.h b/include/xen/page.h index 96294ac93755..9dc46cb8a0fd 100644 --- a/include/xen/page.h +++ b/include/xen/page.h @@ -15,9 +15,9 @@ */ #define xen_pfn_to_page(xen_pfn) \ - ((pfn_to_page(((unsigned long)(xen_pfn) << XEN_PAGE_SHIFT) >> PAGE_SHIFT))) + (pfn_to_page((unsigned long)(xen_pfn) >> (PAGE_SHIFT - XEN_PAGE_SHIFT))) #define page_to_xen_pfn(page) \ - (((page_to_pfn(page)) << PAGE_SHIFT) >> XEN_PAGE_SHIFT) + ((page_to_pfn(page)) << (PAGE_SHIFT - XEN_PAGE_SHIFT)) #define XEN_PFN_PER_PAGE (PAGE_SIZE / XEN_PAGE_SIZE) From dfd74a1edfaba5864276a2859190a8d242d18952 Mon Sep 17 00:00:00 2001 From: Ross Lagerwall Date: Thu, 17 Mar 2016 16:52:00 +0000 Subject: [PATCH 2/3] xen/balloon: Fix crash when ballooning on x86 32 bit PAE Commit 55b3da98a40dbb3776f7454daf0d95dde25c33d2 (xen/balloon: find non-conflicting regions to place hotplugged memory) caused a regression in 4.4. When ballooning on an x86 32 bit PAE system with close to 64 GiB of memory, the address returned by allocate_resource may be above 64 GiB. When using CONFIG_SPARSEMEM, this setup is limited to using physical addresses < 64 GiB. When adding memory at this address, it runs off the end of the mem_section array and causes a crash. Instead, fail the ballooning request. Signed-off-by: Ross Lagerwall Cc: # 4.4+ Signed-off-by: David Vrabel --- drivers/xen/balloon.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c index 9781e0dd59d6..d46839f51e73 100644 --- a/drivers/xen/balloon.c +++ b/drivers/xen/balloon.c @@ -151,6 +151,8 @@ static DECLARE_WAIT_QUEUE_HEAD(balloon_wq); static void balloon_process(struct work_struct *work); static DECLARE_DELAYED_WORK(balloon_worker, balloon_process); +static void release_memory_resource(struct resource *resource); + /* When ballooning out (allocating memory to return to Xen) we don't really want the kernel to try too hard since that can trigger the oom killer. */ #define GFP_BALLOON \ @@ -267,6 +269,20 @@ static struct resource *additional_memory_resource(phys_addr_t size) return NULL; } +#ifdef CONFIG_SPARSEMEM + { + unsigned long limit = 1UL << (MAX_PHYSMEM_BITS - PAGE_SHIFT); + unsigned long pfn = res->start >> PAGE_SHIFT; + + if (pfn > limit) { + pr_err("New System RAM resource outside addressable RAM (%lu > %lu)\n", + pfn, limit); + release_memory_resource(res); + return NULL; + } + } +#endif + return res; } From 27e0e6385377c4dc68a4ddaf1a35a2dfa951f3c5 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Wed, 4 May 2016 07:02:36 -0600 Subject: [PATCH 3/3] xen/evtchn: fix ring resize when binding new events The copying of ring data was wrong for two cases: For a full ring nothing got copied at all (as in that case the canonicalized producer and consumer indexes are identical). And in case one or both of the canonicalized (after the resize) indexes would point into the second half of the buffer, the copied data ended up in the wrong (free) part of the new buffer. In both cases uninitialized data would get passed back to the caller. Fix this by simply copying the old ring contents twice: Once to the low half of the new buffer, and a second time to the high half. This addresses the inability to boot a HVM guest with 64 or more vCPUs. This regression was caused by 8620015499101090 (xen/evtchn: dynamically grow pending event channel ring). Reported-by: Konrad Rzeszutek Wilk Signed-off-by: Jan Beulich Cc: # 4.4+ Signed-off-by: David Vrabel --- drivers/xen/evtchn.c | 20 ++++++++------------ 1 file changed, 8 insertions(+), 12 deletions(-) diff --git a/drivers/xen/evtchn.c b/drivers/xen/evtchn.c index 38272ad24551..f4edd6df3df2 100644 --- a/drivers/xen/evtchn.c +++ b/drivers/xen/evtchn.c @@ -316,7 +316,6 @@ static int evtchn_resize_ring(struct per_user_data *u) { unsigned int new_size; evtchn_port_t *new_ring, *old_ring; - unsigned int p, c; /* * Ensure the ring is large enough to capture all possible @@ -346,20 +345,17 @@ static int evtchn_resize_ring(struct per_user_data *u) /* * Copy the old ring contents to the new ring. * - * If the ring contents crosses the end of the current ring, - * it needs to be copied in two chunks. + * To take care of wrapping, a full ring, and the new index + * pointing into the second half, simply copy the old contents + * twice. * * +---------+ +------------------+ - * |34567 12| -> | 1234567 | - * +-----p-c-+ +------------------+ + * |34567 12| -> |34567 1234567 12| + * +-----p-c-+ +-------c------p---+ */ - p = evtchn_ring_offset(u, u->ring_prod); - c = evtchn_ring_offset(u, u->ring_cons); - if (p < c) { - memcpy(new_ring + c, u->ring + c, (u->ring_size - c) * sizeof(*u->ring)); - memcpy(new_ring + u->ring_size, u->ring, p * sizeof(*u->ring)); - } else - memcpy(new_ring + c, u->ring + c, (p - c) * sizeof(*u->ring)); + memcpy(new_ring, old_ring, u->ring_size * sizeof(*u->ring)); + memcpy(new_ring + u->ring_size, old_ring, + u->ring_size * sizeof(*u->ring)); u->ring = new_ring; u->ring_size = new_size;