Commit 4f169d21 authored Jun 07, 2018 by Paul Mackerras

KVM: PPC: Book3S PR: Don't let PAPR guest set MSR hypervisor bit

PAPR guests run in supervisor mode and should not be able to set the
MSR HV (hypervisor mode) bit or clear the ME (machine check enable)
bit by mtmsrd or any other means. To enforce this, we force MSR_HV
off and MSR_ME on in kvmppc_set_msr_pr. Without this, the guest
can appear to be in hypervisor mode to itself and to userspace.
This has been observed to cause a crash in QEMU when it tries to
deliver a system reset interrupt to the guest.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

parent a50623fb

arch/powerpc/kvm/book3s_pr.c

+4 −0

Original line number	Original line	Diff line number	Diff line
	@@ -456,6 +456,10 @@ static void kvmppc_set_msr_pr(struct kvm_vcpu *vcpu, u64 msr)
	{		{
	ulong old_msr;		ulong old_msr;

			/* For PAPR guest, make sure MSR reflects guest mode */
			if (vcpu->arch.papr_enabled)
			msr = (msr & ~MSR_HV) \| MSR_ME;

	#ifdef EXIT_DEBUG		#ifdef EXIT_DEBUG
	printk(KERN_INFO "KVM: Set MSR to 0x%llx\n", msr);		printk(KERN_INFO "KVM: Set MSR to 0x%llx\n", msr);
	#endif		#endif

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