From 1e326ad429784a16b2b34ec296ff4ca7ad42c220 Mon Sep 17 00:00:00 2001 From: Hou Wenlong Date: Tue, 8 Feb 2022 17:34:05 +0800 Subject: [PATCH] KVM: x86/emulator: Move the unhandled outer privilege level logic of far return into __load_segment_descriptor() Outer-privilege level return is not implemented in emulator, move the unhandled logic into __load_segment_descriptor to make it easier to understand why the checks for RET are incomplete. Suggested-by: Sean Christopherson Signed-off-by: Hou Wenlong Message-Id: <5b7188e6388ac9f4567d14eab32db9adf3e00119.1644292363.git.houwenlong.hwl@antgroup.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/emulate.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 35e69c2a..a60b4d2 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -1623,9 +1623,14 @@ static int __load_segment_descriptor(struct x86_emulate_ctxt *ctxt, if (!(seg_desc.type & 8)) goto exception; - /* RET can never return to an inner privilege level. */ - if (transfer == X86_TRANSFER_RET && rpl < cpl) - goto exception; + if (transfer == X86_TRANSFER_RET) { + /* RET can never return to an inner privilege level. */ + if (rpl < cpl) + goto exception; + /* Outer-privilege level return is not implemented */ + if (rpl > cpl) + return X86EMUL_UNHANDLEABLE; + } if (transfer == X86_TRANSFER_RET || transfer == X86_TRANSFER_TASK_SWITCH) { if (seg_desc.type & 4) { /* conforming */ @@ -2220,9 +2225,6 @@ static int em_ret_far(struct x86_emulate_ctxt *ctxt) rc = emulate_pop(ctxt, &cs, ctxt->op_bytes); if (rc != X86EMUL_CONTINUE) return rc; - /* Outer-privilege level return is not implemented */ - if (ctxt->mode >= X86EMUL_MODE_PROT16 && (cs & 3) > cpl) - return X86EMUL_UNHANDLEABLE; rc = __load_segment_descriptor(ctxt, (u16)cs, VCPU_SREG_CS, cpl, X86_TRANSFER_RET, &new_desc); -- 2.7.4