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x86/kvm: Pass stable clocksource to guests when running nested on Hyper-V 

Currently, KVM is able to work in 'masterclock' mode passing
PVCLOCK_TSC_STABLE_BIT to guests when the clocksource which is used on the
host is TSC.

When running nested on Hyper-V the guest normally uses a different one: TSC
page which is resistant to TSC frequency changes on events like L1
migration. Add support for it in KVM.

The only non-trivial change is in vgettsc(): when updating the gtod copy
both the clock readout and tsc value have to be updated now.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: kvm@vger.kernel.org
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: "Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com>
Cc: Roman Kagan <rkagan@virtuozzo.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: devel@linuxdriverproject.org
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Cathy Avery <cavery@redhat.com>
Cc: Mohammed Gamal <mmorsy@redhat.com>
Link: https://lkml.kernel.org/r/20180124132337.30138-7-vkuznets@redhat.com
hifive-unleashed-5.1
Vitaly Kuznetsov 2018-01-24 14:23:36 +01:00 committed by Thomas Gleixner
parent 51d4e5daa3
commit b0c39dc68e
1 changed files with 68 additions and 25 deletions
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93
arch/x86/kvm/x86.c
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@ -67,6 +67,7 @@
#include <asm/pvclock.h>
#include <asm/div64.h>
#include <asm/irq_remapping.h>
#include <asm/mshyperv.h>
#define CREATE_TRACE_POINTS
#include "trace.h"
@ -1377,6 +1378,11 @@ static u64 compute_guest_tsc(struct kvm_vcpu *vcpu, s64 kernel_ns)
return tsc;
}
static inline int gtod_is_based_on_tsc(int mode)
{
return mode == VCLOCK_TSC || mode == VCLOCK_HVCLOCK;
}
static void kvm_track_tsc_matching(struct kvm_vcpu *vcpu)
{
#ifdef CONFIG_X86_64
@ -1396,7 +1402,7 @@ static void kvm_track_tsc_matching(struct kvm_vcpu *vcpu)
* perform request to enable masterclock.
*/
if (ka->use_master_clock ||
(gtod->clock.vclock_mode == VCLOCK_TSC && vcpus_matched))
(gtod_is_based_on_tsc(gtod->clock.vclock_mode) && vcpus_matched))
kvm_make_request(KVM_REQ_MASTERCLOCK_UPDATE, vcpu);
trace_kvm_track_tsc(vcpu->vcpu_id, ka->nr_vcpus_matched_tsc,
@ -1459,6 +1465,19 @@ static void kvm_vcpu_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
vcpu->arch.tsc_offset = offset;
}
static inline bool kvm_check_tsc_unstable(void)
{
#ifdef CONFIG_X86_64
/*
* TSC is marked unstable when we're running on Hyper-V,
* 'TSC page' clocksource is good.
*/
if (pvclock_gtod_data.clock.vclock_mode == VCLOCK_HVCLOCK)
return false;
#endif
return check_tsc_unstable();
}
void kvm_write_tsc(struct kvm_vcpu *vcpu, struct msr_data *msr)
{
struct kvm *kvm = vcpu->kvm;
@ -1504,7 +1523,7 @@ void kvm_write_tsc(struct kvm_vcpu *vcpu, struct msr_data *msr)
*/
if (synchronizing &&
vcpu->arch.virtual_tsc_khz == kvm->arch.last_tsc_khz) {
if (!check_tsc_unstable()) {
if (!kvm_check_tsc_unstable()) {
offset = kvm->arch.cur_tsc_offset;
pr_debug("kvm: matched tsc offset for %llu\n", data);
} else {
@ -1604,18 +1623,43 @@ static u64 read_tsc(void)
return last;
}
static inline u64 vgettsc(u64 *cycle_now)
static inline u64 vgettsc(u64 *tsc_timestamp, int *mode)
{
long v;
struct pvclock_gtod_data *gtod = &pvclock_gtod_data;
u64 tsc_pg_val;
*cycle_now = read_tsc();
switch (gtod->clock.vclock_mode) {
case VCLOCK_HVCLOCK:
tsc_pg_val = hv_read_tsc_page_tsc(hv_get_tsc_page(),
tsc_timestamp);
if (tsc_pg_val != U64_MAX) {
/* TSC page valid */
*mode = VCLOCK_HVCLOCK;
v = (tsc_pg_val - gtod->clock.cycle_last) &
gtod->clock.mask;
} else {
/* TSC page invalid */
*mode = VCLOCK_NONE;
}
break;
case VCLOCK_TSC:
*mode = VCLOCK_TSC;
*tsc_timestamp = read_tsc();
v = (*tsc_timestamp - gtod->clock.cycle_last) &
gtod->clock.mask;
break;
default:
*mode = VCLOCK_NONE;
}
if (*mode == VCLOCK_NONE)
*tsc_timestamp = v = 0;
v = (*cycle_now - gtod->clock.cycle_last) & gtod->clock.mask;
return v * gtod->clock.mult;
}
static int do_monotonic_boot(s64 *t, u64 *cycle_now)
static int do_monotonic_boot(s64 *t, u64 *tsc_timestamp)
{
struct pvclock_gtod_data *gtod = &pvclock_gtod_data;
unsigned long seq;
@ -1624,9 +1668,8 @@ static int do_monotonic_boot(s64 *t, u64 *cycle_now)
do {
seq = read_seqcount_begin(&gtod->seq);
mode = gtod->clock.vclock_mode;
ns = gtod->nsec_base;
ns += vgettsc(cycle_now);
ns += vgettsc(tsc_timestamp, &mode);
ns >>= gtod->clock.shift;
ns += gtod->boot_ns;
} while (unlikely(read_seqcount_retry(&gtod->seq, seq)));
@ -1635,7 +1678,7 @@ static int do_monotonic_boot(s64 *t, u64 *cycle_now)
return mode;
}
static int do_realtime(struct timespec *ts, u64 *cycle_now)
static int do_realtime(struct timespec *ts, u64 *tsc_timestamp)
{
struct pvclock_gtod_data *gtod = &pvclock_gtod_data;
unsigned long seq;
@ -1644,10 +1687,9 @@ static int do_realtime(struct timespec *ts, u64 *cycle_now)
do {
seq = read_seqcount_begin(&gtod->seq);
mode = gtod->clock.vclock_mode;
ts->tv_sec = gtod->wall_time_sec;
ns = gtod->nsec_base;
ns += vgettsc(cycle_now);
ns += vgettsc(tsc_timestamp, &mode);
ns >>= gtod->clock.shift;
} while (unlikely(read_seqcount_retry(&gtod->seq, seq)));
@ -1657,25 +1699,26 @@ static int do_realtime(struct timespec *ts, u64 *cycle_now)
return mode;
}
/* returns true if host is using tsc clocksource */
static bool kvm_get_time_and_clockread(s64 *kernel_ns, u64 *cycle_now)
/* returns true if host is using TSC based clocksource */
static bool kvm_get_time_and_clockread(s64 *kernel_ns, u64 *tsc_timestamp)
{
/* checked again under seqlock below */
if (pvclock_gtod_data.clock.vclock_mode != VCLOCK_TSC)
if (!gtod_is_based_on_tsc(pvclock_gtod_data.clock.vclock_mode))
return false;
return do_monotonic_boot(kernel_ns, cycle_now) == VCLOCK_TSC;
return gtod_is_based_on_tsc(do_monotonic_boot(kernel_ns,
tsc_timestamp));
}
/* returns true if host is using tsc clocksource */
/* returns true if host is using TSC based clocksource */
static bool kvm_get_walltime_and_clockread(struct timespec *ts,
u64 *cycle_now)
u64 *tsc_timestamp)
{
/* checked again under seqlock below */
if (pvclock_gtod_data.clock.vclock_mode != VCLOCK_TSC)
if (!gtod_is_based_on_tsc(pvclock_gtod_data.clock.vclock_mode))
return false;
return do_realtime(ts, cycle_now) == VCLOCK_TSC;
return gtod_is_based_on_tsc(do_realtime(ts, tsc_timestamp));
}
#endif
@ -2869,13 +2912,13 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
}
if (unlikely(vcpu->cpu != cpu) || check_tsc_unstable()) {
if (unlikely(vcpu->cpu != cpu) || kvm_check_tsc_unstable()) {
s64 tsc_delta = !vcpu->arch.last_host_tsc ? 0 :
rdtsc() - vcpu->arch.last_host_tsc;
if (tsc_delta < 0)
mark_tsc_unstable("KVM discovered backwards TSC");
if (check_tsc_unstable()) {
if (kvm_check_tsc_unstable()) {
u64 offset = kvm_compute_tsc_offset(vcpu,
vcpu->arch.last_guest_tsc);
kvm_vcpu_write_tsc_offset(vcpu, offset);
@ -6110,9 +6153,9 @@ static int pvclock_gtod_notify(struct notifier_block *nb, unsigned long unused,
update_pvclock_gtod(tk);
/* disable master clock if host does not trust, or does not
* use, TSC clocksource
* use, TSC based clocksource.
*/
if (gtod->clock.vclock_mode != VCLOCK_TSC &&
if (!gtod_is_based_on_tsc(gtod->clock.vclock_mode) &&
atomic_read(&kvm_guest_has_master_clock) != 0)
queue_work(system_long_wq, &pvclock_gtod_work);
@ -7767,7 +7810,7 @@ struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm,
{
struct kvm_vcpu *vcpu;
if (check_tsc_unstable() && atomic_read(&kvm->online_vcpus) != 0)
if (kvm_check_tsc_unstable() && atomic_read(&kvm->online_vcpus) != 0)
printk_once(KERN_WARNING
"kvm: SMP vm created on host with unstable TSC; "
"guest TSC will not be reliable\n");
@ -7924,7 +7967,7 @@ int kvm_arch_hardware_enable(void)
return ret;
local_tsc = rdtsc();
stable = !check_tsc_unstable();
stable = !kvm_check_tsc_unstable();
list_for_each_entry(kvm, &vm_list, vm_list) {
kvm_for_each_vcpu(i, vcpu, kvm) {
if (!stable && vcpu->cpu == smp_processor_id())