x86/kvm: Support Hyper-V reenlightenment

Web:        https://git.kernel.org/torvalds/c/0092e4346f49558e5fe5a927c6d78d401dc4ed73
Commit:     0092e4346f49558e5fe5a927c6d78d401dc4ed73
Parent:     b0c39dc68e3b3d22bf9d2984f62f6c86788a49e7
Refname:    refs/heads/master
Author:     Vitaly Kuznetsov <[email protected]>
AuthorDate: Wed Jan 24 14:23:37 2018 +0100
Committer:  Thomas Gleixner <[email protected]>
CommitDate: Tue Jan 30 23:55:34 2018 +0100

    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 <[email protected]>
    Signed-off-by: Thomas Gleixner <[email protected]>
    Acked-by: Paolo Bonzini <[email protected]>
    Cc: Stephen Hemminger <[email protected]>
    Cc: [email protected]
    Cc: Radim Krčmář <[email protected]>
    Cc: Haiyang Zhang <[email protected]>
    Cc: "Michael Kelley (EOSG)" <[email protected]>
    Cc: Roman Kagan <[email protected]>
    Cc: Andy Lutomirski <[email protected]>
    Cc: [email protected]
    Cc: "K. Y. Srinivasan" <[email protected]>
    Cc: Cathy Avery <[email protected]>
    Cc: Mohammed Gamal <[email protected]>
    Link: https://lkml.kernel.org/r/[email protected]
---
 arch/x86/kvm/x86.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b1ce368a07af..879a99987401 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -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);
 
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