| Message ID | 1404839947-1086-137-git-send-email-mdroth@linux.vnet.ibm.com |
|---|---|
| State | New |
| Headers | show |
Il 08/07/2014 19:18, Michael Roth ha scritto: > 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> > (cherry picked from commit a096b3a6732f846ec57dc28b47ee9435aa0609bf) > Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com> > --- > hw/i386/kvm/clock.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 48 insertions(+) > > diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c > index 383938d..be5f867 100644 > --- a/hw/i386/kvm/clock.c > +++ b/hw/i386/kvm/clock.c > @@ -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 @@ typedef struct KVMClockState { > 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 @@ static void kvmclock_vm_state_change(void *opaque, int running, > > 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); > Michael, please skip this patch and the next one, as I'll be reverting them from 2.1 as well. Paolo
diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c index 383938d..be5f867 100644 --- a/hw/i386/kvm/clock.c +++ b/hw/i386/kvm/clock.c @@ -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 @@ typedef struct KVMClockState { 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 @@ static void kvmclock_vm_state_change(void *opaque, int running, 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);