On 05.08.2016 09:49, David Gibson wrote: > On Thu, Aug 04, 2016 at 10:41:16AM +0200, Laurent Vivier wrote: > 1;4402;0c> >> >> On 04/08/2016 04:38, David Gibson wrote: >>> On Wed, Aug 03, 2016 at 09:55:07PM +0200, Laurent Vivier wrote: >>>> If we don't provide the page size in target-ppc:cpu_get_dump_info(), >>>> the default one (TARGET_PAGE_SIZE, 4KB) is used to create >>>> the compressed dump. It works fine with Macintosh, but not with >>>> pseries as the kernel default page size is 64KB. >>>> >>>> Without this patch, if we generate a compressed dump in the QEMU monitor: >>>> >>>> (qemu) dump-guest-memory -z qemu.dump >>>> >>>> This dump cannot be read by crash: >>>> >>>> # crash vmlinux qemu.dump >>>> ... >>>> WARNING: cannot translate vmemmap kernel virtual addresses: >>>> commands requiring page structure contents will fail >>>> ... >>>> >>>> Signed-off-by: Laurent Vivier <lviv...@redhat.com> >>>> --- >>>> target-ppc/arch_dump.c | 5 +++++ >>>> 1 file changed, 5 insertions(+) >>> >>> Urgh.. so, really the page size used by the guest kernel is a >>> guest-side detail, and it's certainly possible to build a 4kiB page >>> guest kernel, although 64kiB is the norm. >> >> virtio-balloon doesn't work with 4K kernel. > > It doesn't? Balloon has rather a lot of flaws, but I didn't think > that was one of them.
It currently doesn't work when the guest uses 4k page size but the host uses 64k page size. Do you remember this bug ticket: https://bugzilla.redhat.com/show_bug.cgi?id=1323988 ? ... we just decided not to spent time on this because no distro is using 4k page size for the pseries platform anymore, and the virtio-balloon code is currently under major reconstruction anyway. Thomas
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