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[Qemu-devel] [PULL 04/11] kvmclock: Ensure time in migration never goes
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PULL 04/11] kvmclock: Ensure time in migration never goes backward |
Date: |
Fri, 26 Sep 2014 16:38:03 +0200 |
From: Alexander Graf <address@hidden>
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 <address@hidden>
Cc: address@hidden
Reviewed-by: Marcelo Tosatti <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
hw/i386/kvm/clock.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 49 insertions(+)
diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c
index 9d65766..1ac60d6 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 "sysemu/cpus.h"
@@ -35,6 +36,48 @@ 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));
+
+ assert(time.tsc_timestamp <= migration_tsc);
+ 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)
@@ -46,9 +89,15 @@ 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);
--
2.1.0
- [Qemu-devel] [PULL 00/11] KVM (and more) patches for 2014-09-26, Paolo Bonzini, 2014/09/26
- [Qemu-devel] [PULL 01/11] pit: fix pit interrupt can't inject into vm after migration, Paolo Bonzini, 2014/09/26
- [Qemu-devel] [PULL 02/11] Introduce cpu_clean_all_dirty, Paolo Bonzini, 2014/09/26
- [Qemu-devel] [PULL 04/11] kvmclock: Ensure time in migration never goes backward,
Paolo Bonzini <=
- [Qemu-devel] [PULL 03/11] kvmclock: Ensure proper env->tsc value for kvmclock_current_nsec calculation, Paolo Bonzini, 2014/09/26
- [Qemu-devel] [PULL 05/11] hw/dma/i8257: Silence phony error message, Paolo Bonzini, 2014/09/26
- [Qemu-devel] [PULL 06/11] target-i386: update fp status fix, Paolo Bonzini, 2014/09/26
- [Qemu-devel] [PULL 08/11] serial: check if backed by a physical serial port at realize time, Paolo Bonzini, 2014/09/26
- [Qemu-devel] [PULL 07/11] serial: reset state at startup, Paolo Bonzini, 2014/09/26
- [Qemu-devel] [PULL 10/11] po: fix conflict with %.mo rule in rules.mak, Paolo Bonzini, 2014/09/26
- [Qemu-devel] [PULL 09/11] kvmvapic: fix migration when VM paused and when not running Windows, Paolo Bonzini, 2014/09/26
- [Qemu-devel] [PULL 11/11] kvm/valgrind: don't mark memory as initialized, Paolo Bonzini, 2014/09/26
- Re: [Qemu-devel] [PULL 00/11] KVM (and more) patches for 2014-09-26, Peter Maydell, 2014/09/26