HTAB size is a factor of maximum memory size that is specified by maxmem= command line option. In cases where there is shortage of host memory, host will not be able to allocate contiguous memory for guest HTAB and will instead allocate a smaller HTAB. This usually is not a problem but when user starts hotplugging memory to the guest, we can run out of HTAB entries and hence memory hotplug fails. This failure should have been handled gracefully by the guest kernel, but currently it leads to guest kernel OOPS. This will eventually get fixed when the handling of memory hotplug is completely moved to kernel for PowerKVM.
Prevent such kernel failure by refusing to boot the guest when requested HTAB size can't be allocated. However HTAB allocation happens in the reset path from where it is too late to abort. Hence this patchset moves the HTAB allocation to machine init and aborts if HTAB size requirement isn't met. This patchset applies against David Gibson's spapr-next. With this patchset, simple boot, reboot and migration tests pass with HV KVM guest. For PR KVM guest, boot and reboot tests were done since migration already appears broken for PR KVM. Changes in v1 ------------- - Correctly handle HTAB for PR KVM guests that use QEMU allocated HTAB. - Verbose error message when aborting. - Check for returned shift value in reset path too and abort when there is mismatch in htab shift values. - Move the marking of htab_fd as stale from spapr_alloc_htab() to spapr_reset_htab() where it originally belonged. v0: http://lists.nongnu.org/archive/html/qemu-devel/2015-09/msg05491.html Bharata B Rao (2): spapr: Allocate HTAB from machine init spapr: Abort when HTAB of requested size isn't allocated hw/ppc/spapr.c | 42 +++++++++++++++++++++++++++++++++++------- 1 file changed, 35 insertions(+), 7 deletions(-) -- 2.1.0
