From 4b6035c2a739bc4c086abbb36f0883a1178a8f1c Mon Sep 17 00:00:00 2001

From: Marcelo Tosatti <mtosatti@redhat.com>

Date: Thu, 26 Jun 2014 15:06:14 +0200

Subject: [PATCH 12/13] kvmclock: Ensure time in migration never goes backward

RH-Author: Marcelo Tosatti <mtosatti@redhat.com>

Message-id: <20140626150716.560273759@amt.cnet>

Patchwork-id: 59388

O-Subject: [RHEL-7.1 qemu-kvm PATCH 1/2] kvmclock: Ensure time in migration never goes backward

Bugzilla: 1098602

RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>

RH-Acked-by: Eduardo Habkost <ehabkost@redhat.com>

RH-Acked-by: Andrew Jones <drjones@redhat.com>

commit a096b3a6732f846ec57dc28b47ee9435aa0609bf upstream

Author: Alexander Graf <agraf@suse.de>

Date:   Fri May 16 17:15:21 2014 +0200

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>

BZ: 1098602

---

 hw/i386/kvm/clock.c |   49 +++++++++++++++++++++++++++++++++++++++++++++++++

 1 file changed, 49 insertions(+)

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

---

 hw/i386/kvm/clock.c |   49 +++++++++++++++++++++++++++++++++++++++++++++++++

 1 files changed, 49 insertions(+), 0 deletions(-)

diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c

index 6d6f3a7..1f2a26e 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"

@@ -28,6 +29,48 @@ 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)

+{

+    CPUArchState *acpu = first_cpu;

+    CPUState *cpu = ENV_GET_CPU(acpu);

+    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)

@@ -39,9 +82,15 @@ 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);

-- 

1.7.1