On Mon, 18 Jul 2016 10:52:36 +1000 David Gibson <da...@gibson.dropbear.id.au> wrote:
> 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(-)
>
> Applied to ppc-for-2.7, thanks.
>
It looks like my replies to this patch were ignored... no big deal though :)
> >
> > 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) {
> > static bool warned;
> > if (!warned) {
> > error_report("Huge page support disabled (n/a for main
> > memory).");
>
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