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Blame SOURCES/kvm-kvmclock-Ensure-time-in-migration-never-goes-backwar.patch

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From 4b6035c2a739bc4c086abbb36f0883a1178a8f1c Mon Sep 17 00:00:00 2001
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From: Marcelo Tosatti <mtosatti@redhat.com>
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Date: Thu, 26 Jun 2014 15:06:14 +0200
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Subject: [PATCH 12/13] kvmclock: Ensure time in migration never goes backward
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RH-Author: Marcelo Tosatti <mtosatti@redhat.com>
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Message-id: <20140626150716.560273759@amt.cnet>
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Patchwork-id: 59388
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O-Subject: [RHEL-7.1 qemu-kvm PATCH 1/2] kvmclock: Ensure time in migration never goes backward
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Bugzilla: 1098602
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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RH-Acked-by: Eduardo Habkost <ehabkost@redhat.com>
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RH-Acked-by: Andrew Jones <drjones@redhat.com>
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commit a096b3a6732f846ec57dc28b47ee9435aa0609bf upstream
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Author: Alexander Graf <agraf@suse.de>
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Date:   Fri May 16 17:15:21 2014 +0200
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When we migrate we ask the kernel about its current belief on what the guest
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time would be. However, I've seen cases where the kvmclock guest structure
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indicates a time more recent than the kvm returned time.
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To make sure we never go backwards, calculate what the guest would have seen
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as time at the point of migration and use that value instead of the kernel
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returned one when it's more recent.  This bases the view of the kvmclock
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after migration on the same foundation in host as well as guest.
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Signed-off-by: Alexander Graf <agraf@suse.de>
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Cc: qemu-stable@nongnu.org
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Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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BZ: 1098602
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---
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 hw/i386/kvm/clock.c |   49 +++++++++++++++++++++++++++++++++++++++++++++++++
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 1 file changed, 49 insertions(+)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 hw/i386/kvm/clock.c |   49 +++++++++++++++++++++++++++++++++++++++++++++++++
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 1 files changed, 49 insertions(+), 0 deletions(-)
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diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c
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index 6d6f3a7..1f2a26e 100644
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--- a/hw/i386/kvm/clock.c
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+++ b/hw/i386/kvm/clock.c
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@@ -14,6 +14,7 @@
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  */
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 #include "qemu-common.h"
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+#include "qemu/host-utils.h"
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 #include "sysemu/sysemu.h"
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 #include "sysemu/kvm.h"
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 #include "hw/sysbus.h"
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@@ -28,6 +29,48 @@ typedef struct KVMClockState {
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     bool clock_valid;
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 } KVMClockState;
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+struct pvclock_vcpu_time_info {
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+    uint32_t   version;
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+    uint32_t   pad0;
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+    uint64_t   tsc_timestamp;
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+    uint64_t   system_time;
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+    uint32_t   tsc_to_system_mul;
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+    int8_t     tsc_shift;
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+    uint8_t    flags;
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+    uint8_t    pad[2];
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+} __attribute__((__packed__)); /* 32 bytes */
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+
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+static uint64_t kvmclock_current_nsec(KVMClockState *s)
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+{
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+    CPUArchState *acpu = first_cpu;
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+    CPUState *cpu = ENV_GET_CPU(acpu);
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+    CPUX86State *env = cpu->env_ptr;
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+    hwaddr kvmclock_struct_pa = env->system_time_msr & ~1ULL;
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+    uint64_t migration_tsc = env->tsc;
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+    struct pvclock_vcpu_time_info time;
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+    uint64_t delta;
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+    uint64_t nsec_lo;
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+    uint64_t nsec_hi;
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+    uint64_t nsec;
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+
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+    if (!(env->system_time_msr & 1ULL)) {
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+        /* KVM clock not active */
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+        return 0;
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+    }
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+
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+    cpu_physical_memory_read(kvmclock_struct_pa, &time, sizeof(time));
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+
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+    delta = migration_tsc - time.tsc_timestamp;
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+    if (time.tsc_shift < 0) {
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+        delta >>= -time.tsc_shift;
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+    } else {
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+        delta <<= time.tsc_shift;
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+    }
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+
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+    mulu64(&nsec_lo, &nsec_hi, delta, time.tsc_to_system_mul);
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+    nsec = (nsec_lo >> 32) | (nsec_hi << 32);
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+    return nsec + time.system_time;
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+}
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 static void kvmclock_vm_state_change(void *opaque, int running,
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                                      RunState state)
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@@ -39,9 +82,15 @@ static void kvmclock_vm_state_change(void *opaque, int running,
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     if (running) {
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         struct kvm_clock_data data;
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+        uint64_t time_at_migration = kvmclock_current_nsec(s);
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         s->clock_valid = false;
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+	/* We can't rely on the migrated clock value, just discard it */
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+	if (time_at_migration) {
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+	        s->clock = time_at_migration;
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+	}
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+
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         data.clock = s->clock;
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         data.flags = 0;
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         ret = kvm_vm_ioctl(kvm_state, KVM_SET_CLOCK, &data);
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-- 
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1.7.1
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