From a096b3a6732f846ec57dc28b47ee9435aa0609bf Mon Sep 17 00:00:00 2001
From: Alexander Graf <agraf@suse.de>
Date: Fri, 16 May 2014 17:15:21 +0200
Subject: kvmclock: Ensure time in migration never goes backward

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>
---
 hw/i386/kvm/clock.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

(limited to 'hw')

diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c
index 892aa025f4..6f4ed28ad4 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);
-- 
cgit v1.2.3


From 9b1786829aefb83f37a8f3135e3ea91c56001b56 Mon Sep 17 00:00:00 2001
From: Marcelo Tosatti <mtosatti@redhat.com>
Date: Tue, 3 Jun 2014 13:34:48 -0300
Subject: kvmclock: Ensure proper env->tsc value for kvmclock_current_nsec
 calculation
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Ensure proper env->tsc value for kvmclock_current_nsec calculation.

Reported-by: Marcin GibuĊ‚a <m.gibula@beyond.pl>
Cc: qemu-stable@nongnu.org
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 hw/i386/kvm/clock.c | 4 ++++
 1 file changed, 4 insertions(+)

(limited to 'hw')

diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c
index 6f4ed28ad4..bef2504389 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));
-- 
cgit v1.2.3