KVM: x86 emulator: Add Virtual-8086 mode of emulation

For some instructions CPU behaves differently for real-mode and
virtual 8086. Let emulator know which mode cpu is in, so it will
not poke into vcpu state directly.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index 9b697c2..784d7c5 100644 (file)
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -168,6 +168,7 @@ struct x86_emulate_ctxt {
 
 /* Execution mode, passed to the emulator. */
 #define X86EMUL_MODE_REAL     0        /* Real mode.             */
+#define X86EMUL_MODE_VM86     1        /* Virtual 8086 mode.     */
 #define X86EMUL_MODE_PROT16   2        /* 16-bit protected mode. */
 #define X86EMUL_MODE_PROT32   4        /* 32-bit protected mode. */
 #define X86EMUL_MODE_PROT64   8        /* 64-bit (long) mode.    */

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 45a4f7c..e4e2df3 100644 (file)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -899,6 +899,7 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
 
        switch (mode) {
        case X86EMUL_MODE_REAL:
+       case X86EMUL_MODE_VM86:
        case X86EMUL_MODE_PROT16:
                def_op_bytes = def_ad_bytes = 2;
                break;
@@ -1525,7 +1526,7 @@ emulate_syscall(struct x86_emulate_ctxt *ctxt)
 
        /* syscall is not available in real mode */
        if (c->lock_prefix || ctxt->mode == X86EMUL_MODE_REAL
-           || !is_protmode(ctxt->vcpu))
+           || ctxt->mode == X86EMUL_MODE_VM86)
                return -1;
 
        setup_syscalls_segments(ctxt, &cs, &ss);
@@ -1577,8 +1578,8 @@ emulate_sysenter(struct x86_emulate_ctxt *ctxt)
        if (c->lock_prefix)
                return -1;
 
-       /* inject #GP if in real mode or paging is disabled */
-       if (ctxt->mode == X86EMUL_MODE_REAL || !is_protmode(ctxt->vcpu)) {
+       /* inject #GP if in real mode */
+       if (ctxt->mode == X86EMUL_MODE_REAL) {
                kvm_inject_gp(ctxt->vcpu, 0);
                return -1;
        }
@@ -1642,8 +1643,9 @@ emulate_sysexit(struct x86_emulate_ctxt *ctxt)
        if (c->lock_prefix)
                return -1;
 
-       /* inject #GP if in real mode or paging is disabled */
-       if (ctxt->mode == X86EMUL_MODE_REAL || !is_protmode(ctxt->vcpu)) {
+       /* inject #GP if in real mode or Virtual 8086 mode */
+       if (ctxt->mode == X86EMUL_MODE_REAL ||
+           ctxt->mode == X86EMUL_MODE_VM86) {
                kvm_inject_gp(ctxt->vcpu, 0);
                return -1;
        }

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b2f91b9..a283795 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3348,8 +3348,9 @@ int emulate_instruction(struct kvm_vcpu *vcpu,
                vcpu->arch.emulate_ctxt.vcpu = vcpu;
                vcpu->arch.emulate_ctxt.eflags = kvm_get_rflags(vcpu);
                vcpu->arch.emulate_ctxt.mode =
+                       (!is_protmode(vcpu)) ? X86EMUL_MODE_REAL :
                        (vcpu->arch.emulate_ctxt.eflags & X86_EFLAGS_VM)
-                       ? X86EMUL_MODE_REAL : cs_l
+                       ? X86EMUL_MODE_VM86 : cs_l
                        ? X86EMUL_MODE_PROT64 : cs_db
                        ? X86EMUL_MODE_PROT32 : X86EMUL_MODE_PROT16;