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ppc: Huge page detection mechanism fixes - Episode III

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After already fixing two issues with the huge page detection mechanism
(see commit 159d2e39a8 and 86b50f2e1b), Greg Kurz noticed another
case that caused the guest to crash where QEMU announces huge pages
though they should not be available for the guest:

qemu-system-ppc64 -enable-kvm ... -mem-path /dev/hugepages \
 -m 1G,slots=4,maxmem=32G
 -object memory-backend-ram,policy=default,size=1G,id=mem-mem1 \
 -device pc-dimm,id=dimm-mem1,memdev=mem-mem1 -smp 2 \
 -numa node,nodeid=0 -numa node,nodeid=1

That means if there is a global mem-path option, we still have
to look at the memory-backend objects that have been specified
additionally and return their minimum page size if that value
is smaller than the page size of the main memory.

Reported-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Tested-by: Greg Kurz <groug@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Thomas Huth 2016-07-18 15:19:04 +02:00 committed by David Gibson
parent 2d2e632ad0
commit 3d4f253483
1 changed files with 14 additions and 13 deletions
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27
target-ppc/kvm.c
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@ -366,10 +366,13 @@ static int find_max_supported_pagesize(Object *obj, void *opaque)
static long getrampagesize(void) static long getrampagesize(void)
{ {
long hpsize = LONG_MAX; long hpsize = LONG_MAX;
long mainrampagesize;
Object *memdev_root; Object *memdev_root;
if (mem_path) { if (mem_path) {
return gethugepagesize(mem_path); mainrampagesize = gethugepagesize(mem_path);
} else {
mainrampagesize = getpagesize();
} }
/* it's possible we have memory-backend objects with /* it's possible we have memory-backend objects with
@ -383,28 +386,26 @@ static long getrampagesize(void)
* backend isn't backed by hugepages. * backend isn't backed by hugepages.
*/ */
memdev_root = object_resolve_path("/objects", NULL); memdev_root = object_resolve_path("/objects", NULL);
if (!memdev_root) { if (memdev_root) {
return getpagesize(); object_child_foreach(memdev_root, find_max_supported_pagesize, &hpsize);
} }
if (hpsize == LONG_MAX) {
object_child_foreach(memdev_root, find_max_supported_pagesize, &hpsize); /* No additional memory regions found ==> Report main RAM page size */
return mainrampagesize;
if (hpsize == LONG_MAX || hpsize == getpagesize()) {
return getpagesize();
} }
/* If NUMA is disabled or the NUMA nodes are not backed with a /* If NUMA is disabled or the NUMA nodes are not backed with a
* memory-backend, then there is at least one node using "normal" * memory-backend, then there is at least one node using "normal" RAM,
* RAM. And since normal RAM has not been configured with "-mem-path" * so if its page size is smaller we have got to report that size instead.
* (what we've checked earlier here already), we can not use huge pages!
*/ */
if (nb_numa_nodes == 0 || numa_info[0].node_memdev == NULL) { if (hpsize > mainrampagesize &&
(nb_numa_nodes == 0 || numa_info[0].node_memdev == NULL)) {
static bool warned; static bool warned;
if (!warned) { if (!warned) {
error_report("Huge page support disabled (n/a for main memory)."); error_report("Huge page support disabled (n/a for main memory).");
warned = true; warned = true;
} }
return getpagesize(); return mainrampagesize;
} }
return hpsize; return hpsize;