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x86/kvm: Support Hyper-V reenlightenment 

When running nested KVM on Hyper-V guests its required to update
masterclocks for all guests when L1 migrates to a host with different TSC
frequency.

Implement the procedure in the following way:
  - Pause all guests.
  - Tell the host (Hyper-V) to stop emulating TSC accesses.
  - Update the gtod copy, recompute clocks.
  - Unpause all guests.

This is somewhat similar to cpufreq but there are two important differences:
 - TSC emulation can only be disabled globally (on all CPUs)
 - The new TSC frequency is not known until emulation is turned off so
   there is no way to 'prepare' for the event upfront.

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/20180124132337.30138-8-vkuznets@redhat.com
hifive-unleashed-5.1
Vitaly Kuznetsov 2018-01-24 14:23:37 +01:00 committed by Thomas Gleixner
parent b0c39dc68e
commit 0092e4346f
1 changed files with 45 additions and 0 deletions
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45
arch/x86/kvm/x86.c
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@ -68,6 +68,7 @@
#include <asm/div64.h>
#include <asm/irq_remapping.h>
#include <asm/mshyperv.h>
#include <asm/hypervisor.h>
#define CREATE_TRACE_POINTS
#include "trace.h"
@ -5932,6 +5933,43 @@ static void tsc_khz_changed(void *data)
__this_cpu_write(cpu_tsc_khz, khz);
}
static void kvm_hyperv_tsc_notifier(void)
{
#ifdef CONFIG_X86_64
struct kvm *kvm;
struct kvm_vcpu *vcpu;
int cpu;
spin_lock(&kvm_lock);
list_for_each_entry(kvm, &vm_list, vm_list)
kvm_make_mclock_inprogress_request(kvm);
hyperv_stop_tsc_emulation();
/* TSC frequency always matches when on Hyper-V */
for_each_present_cpu(cpu)
per_cpu(cpu_tsc_khz, cpu) = tsc_khz;
kvm_max_guest_tsc_khz = tsc_khz;
list_for_each_entry(kvm, &vm_list, vm_list) {
struct kvm_arch *ka = &kvm->arch;
spin_lock(&ka->pvclock_gtod_sync_lock);
pvclock_update_vm_gtod_copy(kvm);
kvm_for_each_vcpu(cpu, vcpu, kvm)
kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
kvm_for_each_vcpu(cpu, vcpu, kvm)
kvm_clear_request(KVM_REQ_MCLOCK_INPROGRESS, vcpu);
spin_unlock(&ka->pvclock_gtod_sync_lock);
}
spin_unlock(&kvm_lock);
#endif
}
static int kvmclock_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
void *data)
{
@ -6217,6 +6255,9 @@ int kvm_arch_init(void *opaque)
kvm_lapic_init();
#ifdef CONFIG_X86_64
pvclock_gtod_register_notifier(&pvclock_gtod_notifier);
if (x86_hyper_type == X86_HYPER_MS_HYPERV)
set_hv_tscchange_cb(kvm_hyperv_tsc_notifier);
#endif
return 0;
@ -6229,6 +6270,10 @@ out:
void kvm_arch_exit(void)
{
#ifdef CONFIG_X86_64
if (x86_hyper_type == X86_HYPER_MS_HYPERV)
clear_hv_tscchange_cb();
#endif
kvm_lapic_exit();
perf_unregister_guest_info_callbacks(&kvm_guest_cbs);