On Mon, Jul 18, 2016 at 03:19:04PM +0200, Thomas Huth wrote: > After already fixing two issues with the huge page detection mechanism > (see commit 159d2e39a860 and 86b50f2e1bef), 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 <gr...@kaod.org> > Signed-off-by: Thomas Huth <th...@redhat.com>
Applied to ppc-for-2.7, thanks.
> ---
> target-ppc/kvm.c | 27 ++++++++++++++-------------
> 1 file changed, 14 insertions(+), 13 deletions(-)
>
> diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
> index 7a8f555..97ab450 100644
> --- a/target-ppc/kvm.c
> +++ b/target-ppc/kvm.c
> @@ -366,10 +366,13 @@ static int find_max_supported_pagesize(Object *obj,
> void *opaque)
> static long getrampagesize(void)
> {
> long hpsize = LONG_MAX;
> + long mainrampagesize;
> Object *memdev_root;
>
> if (mem_path) {
> - return gethugepagesize(mem_path);
> + mainrampagesize = gethugepagesize(mem_path);
> + } else {
> + mainrampagesize = getpagesize();
> }
>
> /* it's possible we have memory-backend objects with
> @@ -383,28 +386,26 @@ static long getrampagesize(void)
> * backend isn't backed by hugepages.
> */
> memdev_root = object_resolve_path("/objects", NULL);
> - if (!memdev_root) {
> - return getpagesize();
> + if (memdev_root) {
> + object_child_foreach(memdev_root, find_max_supported_pagesize,
> &hpsize);
> }
> -
> - object_child_foreach(memdev_root, find_max_supported_pagesize, &hpsize);
> -
> - if (hpsize == LONG_MAX || hpsize == getpagesize()) {
> - return getpagesize();
> + if (hpsize == LONG_MAX) {
> + /* No additional memory regions found ==> Report main RAM page size
> */
> + return mainrampagesize;
> }
>
> /* If NUMA is disabled or the NUMA nodes are not backed with a
> - * memory-backend, then there is at least one node using "normal"
> - * RAM. And since normal RAM has not been configured with "-mem-path"
> - * (what we've checked earlier here already), we can not use huge pages!
> + * memory-backend, then there is at least one node using "normal" RAM,
> + * so if its page size is smaller we have got to report that size
> instead.
> */
> - 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;
> if (!warned) {
> error_report("Huge page support disabled (n/a for main
> memory).");
> warned = true;
> }
> - return getpagesize();
> + return mainrampagesize;
> }
>
> return hpsize;
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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