Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 0092e434 authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by Thomas Gleixner
Browse files

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: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarPaolo 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
parent b0c39dc6

arch/x86/kvm/x86.c

+45 −0
Original line number Diff line number Diff line
@@ -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 @@ int kvm_arch_init(void *opaque) 


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);