On Tue, Dec 02, 2014 at 11:09:03AM +0100, Andrew Jones wrote: > On Mon, Dec 01, 2014 at 03:49:43PM +0000, Richard W.M. Jones wrote: > > According to Documentation/arm64/booting.txt the dtb can occupy the > > same page as the initrd. In fact qemu aligns it to 4K. However on a > > kernel with 64K pages, you can end up freeing part of the device tree > > when the initrd RAM is freed, causing bugs like this one: > > > > https://bugs.launchpad.net/qemu/+bug/1383857 > > > > Don't free partial first/last page when freeing initrd. > > > > Signed-off-by: Richard W.M. Jones <rjones@xxxxxxxxxx> > > --- > > arch/arm64/mm/init.c | 7 ++++--- > > 1 file changed, 4 insertions(+), 3 deletions(-) > > > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > > index 494297c..77bdc39 100644 > > --- a/arch/arm64/mm/init.c > > +++ b/arch/arm64/mm/init.c > > @@ -335,11 +335,12 @@ void free_initrd_mem(unsigned long start, unsigned long end) > > { > > if (!keep_initrd) { > > if (start == initrd_start) > > - start = round_down(start, PAGE_SIZE); > > + start = round_up(start, PAGE_SIZE); > > if (end == initrd_end) > > - end = round_up(end, PAGE_SIZE); > > + end = round_down(end, PAGE_SIZE); > > > > - free_reserved_area((void *)start, (void *)end, 0, "initrd"); > > + if (start < end) > > + free_reserved_area((void *)start, (void *)end, 0, "initrd"); > > } > > } > > What about the equivalent fix for arch/arm/mm/init.c? My assumption was that because pages are always 4K on armv7, and because qemu has always aligned the dtb to 4K, that this couldn't affect armv7. (It's still an unstated assumption in the boot spec which just says the dtb must be aligned to 64 bits.) I'm pretty sure no one has seen this bug on armv7 -- it would be very obvious by now if it was happening there. > Should probably > post to linux-arm-kernel@xxxxxxxxxxxxxxxxxxx and linux-kernel@xxxxxxxxxxxxxxx Thanks. I'm quite happy for someone to come up with a better way to fix this .. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-p2v converts physical machines to virtual machines. Boot with a live CD or over the network (PXE) and turn machines into KVM guests. http://libguestfs.org/virt-v2v _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
