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[Qemu-devel] Re: [PATCH v4 07/10] qemu-kvm: Cleanup/fix TSC and PV clock
From: |
Jan Kiszka |
Subject: |
[Qemu-devel] Re: [PATCH v4 07/10] qemu-kvm: Cleanup/fix TSC and PV clock writeback |
Date: |
Thu, 25 Feb 2010 16:56:54 +0100 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
Drop kvm_load_tsc in favor of level-dependent writeback in
kvm_arch_load_regs. KVM's PV clock MSRs fall in the same category and
should therefore only be written back on full sync.
Signed-off-by: Jan Kiszka <address@hidden>
---
Changes in v4:
- only write TSC MSRs of SMP guests if they are non-zero, ie. after
migration (behavior of original code)
qemu-kvm-x86.c | 27 +++++++++++++--------------
qemu-kvm.h | 4 ----
target-i386/machine.c | 5 -----
3 files changed, 13 insertions(+), 23 deletions(-)
diff --git a/qemu-kvm-x86.c b/qemu-kvm-x86.c
index 840c1c9..285c05a 100644
--- a/qemu-kvm-x86.c
+++ b/qemu-kvm-x86.c
@@ -965,8 +965,19 @@ void kvm_arch_load_regs(CPUState *env, int level)
set_msr_entry(&msrs[n++], MSR_LSTAR , env->lstar);
}
#endif
- set_msr_entry(&msrs[n++], MSR_KVM_SYSTEM_TIME, env->system_time_msr);
- set_msr_entry(&msrs[n++], MSR_KVM_WALL_CLOCK, env->wall_clock_msr);
+ if (level == KVM_PUT_FULL_STATE) {
+ /*
+ * KVM is yet unable to synchronize TSC values of multiple VCPUs on
+ * writeback. Until this is fixed, we only write the offset to SMP
+ * guests after migration, desynchronizing the VCPUs, but avoiding
+ * huge jump-backs that would occur without any writeback at all.
+ */
+ if (smp_cpus == 1 || env->tsc != 0) {
+ set_msr_entry(&msrs[n++], MSR_IA32_TSC, env->tsc);
+ }
+ set_msr_entry(&msrs[n++], MSR_KVM_SYSTEM_TIME, env->system_time_msr);
+ set_msr_entry(&msrs[n++], MSR_KVM_WALL_CLOCK, env->wall_clock_msr);
+ }
rc = kvm_set_msrs(env, msrs, n);
if (rc == -1)
@@ -986,18 +997,6 @@ void kvm_arch_load_regs(CPUState *env, int level)
kvm_guest_debug_workarounds(env);
}
-void kvm_load_tsc(CPUState *env)
-{
- int rc;
- struct kvm_msr_entry msr;
-
- set_msr_entry(&msr, MSR_IA32_TSC, env->tsc);
-
- rc = kvm_set_msrs(env, &msr, 1);
- if (rc == -1)
- perror("kvm_set_tsc FAILED.\n");
-}
-
void kvm_arch_save_regs(CPUState *env)
{
struct kvm_regs regs;
diff --git a/qemu-kvm.h b/qemu-kvm.h
index c6ff652..827cac5 100644
--- a/qemu-kvm.h
+++ b/qemu-kvm.h
@@ -958,7 +958,6 @@ int handle_tpr_access(void *opaque, CPUState *env, uint64_t
rip,
#ifdef TARGET_I386
#define qemu_kvm_has_pit_state2() kvm_has_pit_state2(kvm_context)
#endif
-void kvm_load_tsc(CPUState *env);
#else
#define kvm_nested 0
#define qemu_kvm_has_gsi_routing() (0)
@@ -966,9 +965,6 @@ void kvm_load_tsc(CPUState *env);
#define qemu_kvm_has_pit_state2() (0)
#endif
#define qemu_kvm_cpu_stop(env) do {} while(0)
-static inline void kvm_load_tsc(CPUState *env)
-{
-}
#endif
void kvm_mutex_unlock(void);
diff --git a/target-i386/machine.c b/target-i386/machine.c
index bcc315b..b547e2a 100644
--- a/target-i386/machine.c
+++ b/target-i386/machine.c
@@ -354,11 +354,6 @@ static int cpu_post_load(void *opaque, int version_id)
hw_breakpoint_insert(env, i);
tlb_flush(env, 1);
-
- if (kvm_enabled()) {
- kvm_load_tsc(env);
- }
-
return 0;
}
- [Qemu-devel] [PATCH v3 07/10] qemu-kvm: Cleanup/fix TSC and PV clock writeback, (continued)
- [Qemu-devel] [PATCH v3 07/10] qemu-kvm: Cleanup/fix TSC and PV clock writeback, Jan Kiszka, 2010/02/24
- [Qemu-devel] Re: [PATCH v3 07/10] qemu-kvm: Cleanup/fix TSC and PV clock writeback, Marcelo Tosatti, 2010/02/24
- [Qemu-devel] Re: [PATCH v3 07/10] qemu-kvm: Cleanup/fix TSC and PV clock writeback, Jan Kiszka, 2010/02/24
- [Qemu-devel] Re: [PATCH v3 07/10] qemu-kvm: Cleanup/fix TSC and PV clock writeback, Marcelo Tosatti, 2010/02/24
- [Qemu-devel] Re: [PATCH v3 07/10] qemu-kvm: Cleanup/fix TSC and PV clock writeback, Jan Kiszka, 2010/02/24
- [Qemu-devel] Re: [PATCH v3 07/10] qemu-kvm: Cleanup/fix TSC and PV clock writeback, Marcelo Tosatti, 2010/02/24
- [Qemu-devel] Re: [PATCH v3 07/10] qemu-kvm: Cleanup/fix TSC and PV clock writeback, Jan Kiszka, 2010/02/25
- [Qemu-devel] Re: [PATCH v3 07/10] qemu-kvm: Cleanup/fix TSC and PV clock writeback, Marcelo Tosatti, 2010/02/25
- [Qemu-devel] Re: [PATCH v3 07/10] qemu-kvm: Cleanup/fix TSC and PV clock writeback, Jan Kiszka, 2010/02/25
- [Qemu-devel] Re: [PATCH v3 07/10] qemu-kvm: Cleanup/fix TSC and PV clock writeback, Marcelo Tosatti, 2010/02/25
[Qemu-devel] Re: [PATCH v4 07/10] qemu-kvm: Cleanup/fix TSC and PV clock writeback,
Jan Kiszka <=
[Qemu-devel] Re: [PATCH v3 00/10] qemu-kvm: Hook cleanups and yet more use of upstream code, Marcelo Tosatti, 2010/02/24