| Message ID | 20140905135539.188955270@amt.cnet |
|---|---|
| State | New |
| Headers | show |
Ping? On Fri, Sep 05, 2014 at 10:52:45AM -0300, Marcelo Tosatti wrote: > From: Alexander Graf <agraf@suse.de> > > When we migrate we ask the kernel about its current belief on what the guest > time would be. However, I've seen cases where the kvmclock guest structure > indicates a time more recent than the kvm returned time. > > To make sure we never go backwards, calculate what the guest would have seen as time at the point of migration and use that value instead of the kernel returned one when it's more recent. > This bases the view of the kvmclock after migration on the > same foundation in host as well as guest. > > Signed-off-by: Alexander Graf <agraf@suse.de> > Cc: qemu-stable@nongnu.org > Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com> > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Who are you pinging? Alex On 09.09.14 17:12, Marcelo Tosatti wrote: > Ping? > > On Fri, Sep 05, 2014 at 10:52:45AM -0300, Marcelo Tosatti wrote: >> From: Alexander Graf <agraf@suse.de> >> >> When we migrate we ask the kernel about its current belief on what the guest >> time would be. However, I've seen cases where the kvmclock guest structure >> indicates a time more recent than the kvm returned time. >> >> To make sure we never go backwards, calculate what the guest would have seen as time at the point of migration and use that value instead of the kernel returned one when it's more recent. >> This bases the view of the kvmclock after migration on the >> same foundation in host as well as guest. >> >> Signed-off-by: Alexander Graf <agraf@suse.de> >> Cc: qemu-stable@nongnu.org >> Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com> >> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > >
On Tue, Sep 09, 2014 at 11:16:45PM +0200, Alexander Graf wrote:
> Who are you pinging?
Paolo.
Index: qemu/hw/i386/kvm/clock.c =================================================================== --- qemu.orig/hw/i386/kvm/clock.c 2014-08-15 15:43:30.440191065 -0300 +++ qemu/hw/i386/kvm/clock.c 2014-08-15 15:56:31.754875109 -0300 @@ -14,6 +14,7 @@ */ #include "qemu-common.h" +#include "qemu/host-utils.h" #include "sysemu/sysemu.h" #include "sysemu/kvm.h" #include "hw/sysbus.h" @@ -34,6 +35,47 @@ bool clock_valid; } KVMClockState; +struct pvclock_vcpu_time_info { + uint32_t version; + uint32_t pad0; + uint64_t tsc_timestamp; + uint64_t system_time; + uint32_t tsc_to_system_mul; + int8_t tsc_shift; + uint8_t flags; + uint8_t pad[2]; +} __attribute__((__packed__)); /* 32 bytes */ + +static uint64_t kvmclock_current_nsec(KVMClockState *s) +{ + CPUState *cpu = first_cpu; + CPUX86State *env = cpu->env_ptr; + hwaddr kvmclock_struct_pa = env->system_time_msr & ~1ULL; + uint64_t migration_tsc = env->tsc; + struct pvclock_vcpu_time_info time; + uint64_t delta; + uint64_t nsec_lo; + uint64_t nsec_hi; + uint64_t nsec; + + if (!(env->system_time_msr & 1ULL)) { + /* KVM clock not active */ + return 0; + } + + cpu_physical_memory_read(kvmclock_struct_pa, &time, sizeof(time)); + + delta = migration_tsc - time.tsc_timestamp; + if (time.tsc_shift < 0) { + delta >>= -time.tsc_shift; + } else { + delta <<= time.tsc_shift; + } + + mulu64(&nsec_lo, &nsec_hi, delta, time.tsc_to_system_mul); + nsec = (nsec_lo >> 32) | (nsec_hi << 32); + return nsec + time.system_time; +} static void kvmclock_vm_state_change(void *opaque, int running, RunState state) @@ -45,9 +87,15 @@ if (running) { struct kvm_clock_data data; + uint64_t time_at_migration = kvmclock_current_nsec(s); s->clock_valid = false; + /* We can't rely on the migrated clock value, just discard it */ + if (time_at_migration) { + s->clock = time_at_migration; + } + data.clock = s->clock; data.flags = 0; ret = kvm_vm_ioctl(kvm_state, KVM_SET_CLOCK, &data);