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Commit e59d24e6 authored by Greg Kurz's avatar Greg Kurz Committed by Paul Mackerras
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KVM: PPC: Book3S HV: Fix incorrect userspace exit on ioeventfd write 



When the guest does an MMIO write which is handled successfully by an
ioeventfd, ioeventfd_write() returns 0 (success) and
kvmppc_handle_store() returns EMULATE_DONE.  Then
kvmppc_emulate_mmio() converts EMULATE_DONE to RESUME_GUEST_NV and
this causes an exit from the loop in kvmppc_vcpu_run_hv(), causing an
exit back to userspace with a bogus exit reason code, typically
causing userspace (e.g. qemu) to crash with a message about an unknown
exit code.

This adds handling of RESUME_GUEST_NV in kvmppc_vcpu_run_hv() in order
to fix that.  For generality, we define a helper to check for either
of the return-to-guest codes we use, RESUME_GUEST and RESUME_GUEST_NV,
to make it easy to check for either and provide one place to update if
any other return-to-guest code gets defined in future.

Since it only affects Book3S HV for now, the helper is added to
the kvm_book3s.h header file.

We use the helper in two places in kvmppc_run_core() as well for
future-proofing, though we don't see RESUME_GUEST_NV in either place
at present.

[paulus@samba.org - combined 4 patches into one, rewrote description]

Suggested-by: default avatarPaul Mackerras <paulus@samba.org>
Signed-off-by: default avatarAlexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: default avatarGreg Kurz <gkurz@linux.vnet.ibm.com>
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
parent e724f080

arch/powerpc/include/asm/kvm_book3s.h

+5 −0
Original line number Diff line number Diff line
@@ -304,6 +304,11 @@ static inline ulong kvmppc_get_fault_dar(struct kvm_vcpu *vcpu) 
	return vcpu->arch.fault_dar;

}



static inline bool is_kvmppc_resume_guest(int r)

{

	return (r == RESUME_GUEST || r == RESUME_GUEST_NV);

}



/* Magic register values loaded into r3 and r4 before the 'sc' assembly

 * instruction for the OSI hypercalls */

#define OSI_SC_MAGIC_R3			0x113724FA

arch/powerpc/kvm/book3s_hv.c

+3 −3
Original line number Diff line number Diff line
@@ -1530,7 +1530,7 @@ static void kvmppc_run_core(struct kvmppc_vcore *vc) 
		vcpu->arch.trap = 0;



		if (vcpu->arch.ceded) {

			if (ret != RESUME_GUEST)

			if (!is_kvmppc_resume_guest(ret))

				kvmppc_end_cede(vcpu);

			else

				kvmppc_set_timer(vcpu);
@@ -1541,7 +1541,7 @@ static void kvmppc_run_core(struct kvmppc_vcore *vc) 
	vc->vcore_state = VCORE_INACTIVE;

	list_for_each_entry_safe(vcpu, vnext, &vc->runnable_threads,

				 arch.run_list) {

		if (vcpu->arch.ret != RESUME_GUEST) {

		if (!is_kvmppc_resume_guest(vcpu->arch.ret)) {

			kvmppc_remove_runnable(vc, vcpu);

			wake_up(&vcpu->arch.cpu_run);

		}
@@ -1731,7 +1731,7 @@ static int kvmppc_vcpu_run_hv(struct kvm_run *run, struct kvm_vcpu *vcpu) 
				vcpu->arch.fault_dar, vcpu->arch.fault_dsisr);

			srcu_read_unlock(&vcpu->kvm->srcu, srcu_idx);

		}

	} while (r == RESUME_GUEST);

	} while (is_kvmppc_resume_guest(r));



 out:

	vcpu->arch.state = KVMPPC_VCPU_NOTREADY;