redonkable
/
alistair23-linux
1
0
Fork 0
Code Releases Activity

KVM: x86: make backwards_tsc_observed a per-VM variable 

The backwards_tsc_observed global introduced in commit 16a9602 is never
reset to false. If a VM happens to be running while the host is suspended
(a common source of the TSC jumping backwards), master clock will never
be enabled again for any VM. In contrast, if no VM is running while the
host is suspended, master clock is unaffected. This is inconsistent and
unnecessarily strict. Let's track the backwards_tsc_observed variable
separately and let each VM start with a clean slate.

Real world impact: My Windows VMs get slower after my laptop undergoes a
suspend/resume cycle. The only way to get the perf back is unloading and
reloading the kvm module.

Signed-off-by: Ladi Prosek <lprosek@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
hifive-unleashed-5.1
Ladi Prosek 2017-06-26 09:56:43 +02:00 committed by Radim Krčmář
parent 286de8f6ac
commit a826faf108
2 changed files with 3 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/x86/include/asm/kvm_host.h
View File

@ -803,6 +803,7 @@ struct kvm_arch {
int audit_point;
#endif
bool backwards_tsc_observed;
bool boot_vcpu_runs_old_kvmclock;
u32 bsp_vcpu_id;

6
arch/x86/kvm/x86.c
View File

@ -134,8 +134,6 @@ module_param(lapic_timer_advance_ns, uint, S_IRUGO | S_IWUSR);
static bool __read_mostly vector_hashing = true;
module_param(vector_hashing, bool, S_IRUGO);
static bool __read_mostly backwards_tsc_observed = false;
#define KVM_NR_SHARED_MSRS 16
struct kvm_shared_msrs_global {
@ -1719,7 +1717,7 @@ static void pvclock_update_vm_gtod_copy(struct kvm *kvm)
&ka->master_cycle_now);
ka->use_master_clock = host_tsc_clocksource && vcpus_matched
&& !backwards_tsc_observed
&& !ka->backwards_tsc_observed
&& !ka->boot_vcpu_runs_old_kvmclock;
if (ka->use_master_clock)
@ -7835,8 +7833,8 @@ int kvm_arch_hardware_enable(void)
*/
if (backwards_tsc) {
u64 delta_cyc = max_tsc - local_tsc;
backwards_tsc_observed = true;
list_for_each_entry(kvm, &vm_list, vm_list) {
kvm->arch.backwards_tsc_observed = true;
kvm_for_each_vcpu(i, vcpu, kvm) {
vcpu->arch.tsc_offset_adjustment += delta_cyc;
vcpu->arch.last_host_tsc = local_tsc;