On Mon, 18 Jul 2016 11:21:41 +0200 Thomas Huth <[email protected]> wrote:
> On 15.07.2016 11:28, Greg Kurz wrote: > > On Fri, 15 Jul 2016 10:10:25 +0200 > > Thomas Huth <[email protected]> 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 > > > > According to http://patchwork.ozlabs.org/patch/584741/ , it is best worded > > > > "Broken in commit 86b50f2e1bef" > > Using the "Fixes:" syntax is a well-known practise with the Linux kernel > (see > http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/SubmittingPatches?id=HEAD#n187), > so I don't see the point why we should introduce another syntax for QEMU > here. And if we do, it should be documented on > http://qemu-project.org/Contribute/SubmitAPatch at least. > > Thomas > I had used this syntax in the first place at the time, but Markus's and David's comments lured me into believing there was a consensus against it. FWIW, I personally prefer the Linux kernel "Fixes:" syntax :) Cheers. -- Greg
