[PATCH 12/20] KVM: x86 emulator: Add Virtual-8086 mode of emulation

Avi Kivity
2010-02-17T13:45:36Z

From: Gleb Natapov <gleb@redhat.com>

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>
---
arch/x86/include/asm/kvm_emulate.h | 1 +
arch/x86/kvm/emulate.c | 12 +++++++-----
arch/x86/kvm/x86.c | 3 ++-
3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index 9b697c2..784d7c5 100644
--- 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
--- 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
--- 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;

--
1.6.5.3