On Fri, Jul 15, 2016 at 10:10:25AM +0200, Thomas Huth wrote: > Commit 86b50f2e1bef ("Disable huge page support if it is not available > for main RAM") already made sure that huge page support is not announced > to the guest if the normal RAM of non-NUMA configurations is not backed > by a huge page filesystem. However, there is one more case that can go > wrong: NUMA is enabled, but the RAM of the NUMA nodes are not configured > with huge page support (and only the memory of a DIMM is configured with > it). When QEMU is started with the following command line for example, > the Linux guest currently crashes because it is trying to use huge pages > on a memory region that does not support huge pages: > > qemu-system-ppc64 -enable-kvm ... -m 1G,slots=4,maxmem=32G -object \ > memory-backend-file,policy=default,mem-path=/hugepages,size=1G,id=mem-mem1 > \ > -device pc-dimm,id=dimm-mem1,memdev=mem-mem1 -smp 2 \ > -numa node,nodeid=0 -numa node,nodeid=1 > > To fix this issue, we've got to make sure to disable huge page support, > too, when there is a NUMA node that is not using a memory backend with > huge page support. > > Fixes: 86b50f2e1befc33407bdfeb6f45f7b0d2439a740 > Signed-off-by: Thomas Huth <th...@redhat.com> > --- > target-ppc/kvm.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c > index 884d564..7a8f555 100644 > --- a/target-ppc/kvm.c > +++ b/target-ppc/kvm.c > @@ -389,12 +389,16 @@ static long getrampagesize(void) > > object_child_foreach(memdev_root, find_max_supported_pagesize, &hpsize); > > - if (hpsize == LONG_MAX) { > + if (hpsize == LONG_MAX || hpsize == getpagesize()) { > return getpagesize(); > } > > - if (nb_numa_nodes == 0 && hpsize > getpagesize()) { > - /* No NUMA nodes and normal RAM without -mem-path ==> no huge pages! > */ > + /* 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! > + */ > + if (nb_numa_nodes == 0 || numa_info[0].node_memdev == NULL) {
Is that second clause sufficient, or do you need to loop through and check the memdev of every node? > static bool warned; > if (!warned) { > error_report("Huge page support disabled (n/a for main > memory)."); -- 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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