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Commit 8f6055cb authored by Joerg Roedel's avatar Joerg Roedel Committed by Avi Kivity
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KVM: X86: Make tsc_delta calculation a function of guest tsc 



The calculation of the tsc_delta value to ensure a
forward-going tsc for the guest is a function of the
host-tsc. This works as long as the guests tsc_khz is equal
to the hosts tsc_khz. With tsc-scaling hardware support this
is not longer true and the tsc_delta needs to be calculated
using guest_tsc values.

Signed-off-by: default avatarJoerg Roedel <joerg.roedel@amd.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 1e993611

arch/x86/kvm/x86.c

+7 −2
Original line number Diff line number Diff line
@@ -2113,8 +2113,13 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) 
	kvm_x86_ops->vcpu_load(vcpu, cpu);

	if (unlikely(vcpu->cpu != cpu) || check_tsc_unstable()) {

		/* Make sure TSC doesn't go backwards */

		s64 tsc_delta = !vcpu->arch.last_host_tsc ? 0 :

				native_read_tsc() - vcpu->arch.last_host_tsc;

		s64 tsc_delta;

		u64 tsc;



		kvm_get_msr(vcpu, MSR_IA32_TSC, &tsc);

		tsc_delta = !vcpu->arch.last_guest_tsc ? 0 :

			     tsc - vcpu->arch.last_guest_tsc;



		if (tsc_delta < 0)

			mark_tsc_unstable("KVM discovered backwards TSC");

		if (check_tsc_unstable()) {