On 05/11/14 18:57, Alexander Graf wrote: > > > On 05.11.14 07:17, Samuel Mendoza-Jonas wrote: >> If a guest reboots during a running migration, changes to the >> hash page table are not necessarily updated on the destination. >> Opening a new file descriptor to the HTAB forces the migration >> handler to resend the entire table. >> >> Signed-off-by: Samuel Mendoza-Jonas <sam...@au1.ibm.com> >> --- >> hw/ppc/spapr.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++ >> include/hw/ppc/spapr.h | 2 ++ >> 2 files changed, 49 insertions(+) >> >> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c >> index 0a2bfe6..1610c28 100644 >> --- a/hw/ppc/spapr.c >> +++ b/hw/ppc/spapr.c >> @@ -833,6 +833,13 @@ static void spapr_reset_htab(sPAPREnvironment *spapr) >> /* Kernel handles htab, we don't need to allocate one */ >> spapr->htab_shift = shift; >> kvmppc_kern_htab = true; >> + >> + /* Tell readers to update their file descriptor */ >> + pthread_mutex_lock(&spapr->htab_mutex); > > I don't think you can directly use pthread functions in hw/. These files > could be compiled on Windows which doesn't have pthread. Instead, please > use the QEMU wrappers from util/qemu-thread-posix.c.
Thanks for catching this! > > Or maybe try and find out whether you actually do need the lock. Reboots > can only happen when triggered via a HCALL which takes the BQL. I don't > quite know how much the migration code became threaded, but I'd assume > that at least device migration would happen under the BQL or after > stopping the VM, but in a consistent place. > > So as long as we're guaranteed that the htab_fd_stale variable is set at > the final "send all device contents" phase, we should automatically > catch any reset that happened in between - even without a lock, no? Good point, we only really *need* the flag to be set at least before the call to save_live_complete(). I'll double check but yes, that should work. > > > Alex > -- ----------- LTC Ozlabs IBM
