KVM: x86: Handle 32-bit wrap of EIP for EMULTYPE_SKIP with flat code seg

Truncate the new EIP to a 32-bit value when handling EMULTYPE_SKIP as the
decode phase does not truncate _eip.  Wrapping the 32-bit boundary is
legal if and only if CS is a flat code segment, but that check is
implicitly handled in the form of limit checks in the decode phase.

Opportunstically prepare for a future fix by storing the result of any
truncation in "eip" instead of "_eip".

Fixes: 1957aa63be53 ("KVM: VMX: Handle single-step #DB for EMULTYPE_SKIP on EPT misconfig")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <093eabb1eab2965201c9b018373baf26ff256d85.1635842679.git.houwenlong93@linux.alibaba.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2f232eb..d0cc405 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8139,7 +8139,12 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
         * updating interruptibility state and injecting single-step #DBs.
         */
        if (emulation_type & EMULTYPE_SKIP) {
-               kvm_rip_write(vcpu, ctxt->_eip);
+               if (ctxt->mode != X86EMUL_MODE_PROT64)
+                       ctxt->eip = (u32)ctxt->_eip;
+               else
+                       ctxt->eip = ctxt->_eip;
+
+               kvm_rip_write(vcpu, ctxt->eip);
                if (ctxt->eflags & X86_EFLAGS_RF)
                        kvm_set_rflags(vcpu, ctxt->eflags & ~X86_EFLAGS_RF);
                return 1;