On Mon, Jun 02, 2014 at 10:31:44PM +0200, Marcin Gibuła wrote: > >+ cpu_physical_memory_read(kvmclock_struct_pa, &time, sizeof(time)); > >+ > >+ delta = migration_tsc - time.tsc_timestamp; > > Hi, > > when I was testing live storage migration with libvirt I found out > that this patch can cause virtual machine to hang when completing > mirror job. > > This is (probably) because kvmclock_current_nsec() is called twice > in a row and on second call time.tsc_timestamp is larger than > migration_tsc. This causes delta to be huge and sets timer to > invalid value. > > The double call happens when switching from old to new disk > (pivoting in libvirt's nomenclature). > > Example values: > > First call: migration_tsc: 12052203518652476, time_tsc: > 12052203301565676, delta 108543400 > > Second call: migration_tsc: 12052203518652476, time_tsc: > 12052204478600322, delta 9223372036374801885 > > Perhaps it is worth adding: > > if (time.tsc_timestamp > migration_tsc) { > return 0; > } > > there? Untested though...
Hi Marcin, Can you give this patch a try? Should read the guest TSC values after stopping the VM. diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c index 6f4ed28a..bef2504 100644 --- a/hw/i386/kvm/clock.c +++ b/hw/i386/kvm/clock.c @@ -17,6 +17,7 @@ #include "qemu/host-utils.h" #include "sysemu/sysemu.h" #include "sysemu/kvm.h" +#include "sysemu/cpus.h" #include "hw/sysbus.h" #include "hw/kvm/clock.h" @@ -65,6 +66,7 @@ static uint64_t kvmclock_current_nsec(KVMClockState *s) cpu_physical_memory_read(kvmclock_struct_pa, &time, sizeof(time)); + assert(time.tsc_timestamp <= migration_tsc); delta = migration_tsc - time.tsc_timestamp; if (time.tsc_shift < 0) { delta >>= -time.tsc_shift; @@ -123,6 +125,8 @@ static void kvmclock_vm_state_change(void *opaque, int running, if (s->clock_valid) { return; } + + cpu_synchronize_all_states(); ret = kvm_vm_ioctl(kvm_state, KVM_GET_CLOCK, &data); if (ret < 0) { fprintf(stderr, "KVM_GET_CLOCK failed: %s\n", strerror(ret));