Commit 5842be1a authored by James Hogan's avatar James Hogan Committed by Luis Henriques

KVM: MIPS: Make ERET handle ERL before EXL

BugLink: http://bugs.launchpad.net/bugs/1642572

commit ede5f3e7 upstream.

The ERET instruction to return from exception is used for returning from
exception level (Status.EXL) and error level (Status.ERL). If both bits
are set however we should be returning from ERL first, as ERL can
interrupt EXL, for example when an NMI is taken. KVM however checks EXL
first.

Fix the order of the checks to match the pseudocode in the instruction
set manual.

Fixes: e685c689 ("KVM/MIPS32: Privileged instruction/target branch emulation.")
Signed-off-by: default avatarJames Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
parent 1aaecfa0
......@@ -752,15 +752,15 @@ enum emulation_result kvm_mips_emul_eret(struct kvm_vcpu *vcpu)
struct mips_coproc *cop0 = vcpu->arch.cop0;
enum emulation_result er = EMULATE_DONE;
if (kvm_read_c0_guest_status(cop0) & ST0_EXL) {
if (kvm_read_c0_guest_status(cop0) & ST0_ERL) {
kvm_clear_c0_guest_status(cop0, ST0_ERL);
vcpu->arch.pc = kvm_read_c0_guest_errorepc(cop0);
} else if (kvm_read_c0_guest_status(cop0) & ST0_EXL) {
kvm_debug("[%#lx] ERET to %#lx\n", vcpu->arch.pc,
kvm_read_c0_guest_epc(cop0));
kvm_clear_c0_guest_status(cop0, ST0_EXL);
vcpu->arch.pc = kvm_read_c0_guest_epc(cop0);
} else if (kvm_read_c0_guest_status(cop0) & ST0_ERL) {
kvm_clear_c0_guest_status(cop0, ST0_ERL);
vcpu->arch.pc = kvm_read_c0_guest_errorepc(cop0);
} else {
kvm_err("[%#lx] ERET when MIPS_SR_EXL|MIPS_SR_ERL == 0\n",
vcpu->arch.pc);
......
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