linux-kernel - [052/197] KVM: x86 emulator: Add Virtual-8086 mode of emulation

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Message-Id: <20100422190912.021005075@kvm.kroah.org>
Date:	Thu, 22 Apr 2010 12:08:23 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Avi Kivity <avi@...hat.com>, Gleb Natapov <gleb@...hat.com>,
	Stefan Bader <stefan.bader@...onical.com>
Subject: [052/197] KVM: x86 emulator: Add Virtual-8086 mode of emulation

2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------


From: Gleb Natapov <gleb@...hat.com>

commit a0044755679f3e761b8b95995e5f2db2b7efd0f6 upstream

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@...hat.com>
Signed-off-by: Avi Kivity <avi@...hat.com>
Signed-off-by: Stefan Bader <stefan.bader@...onical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
 arch/x86/include/asm/kvm_emulate.h |    1 +
 arch/x86/kvm/emulate.c             |   14 +++++++-------
 arch/x86/kvm/x86.c                 |    3 ++-
 3 files changed, 10 insertions(+), 8 deletions(-)

--- 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.    */
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -895,6 +895,7 @@ x86_decode_insn(struct x86_emulate_ctxt
 
 	switch (mode) {
 	case X86EMUL_MODE_REAL:
+	case X86EMUL_MODE_VM86:
 	case X86EMUL_MODE_PROT16:
 		def_op_bytes = def_ad_bytes = 2;
 		break;
@@ -1453,7 +1454,7 @@ emulate_syscall(struct x86_emulate_ctxt
 
 	/* syscall is not available in real mode */
 	if (c->lock_prefix || ctxt->mode == X86EMUL_MODE_REAL
-		|| !(ctxt->vcpu->arch.cr0 & X86_CR0_PE))
+	    || ctxt->mode == X86EMUL_MODE_VM86)
 		return -1;
 
 	setup_syscalls_segments(ctxt, &cs, &ss);
@@ -1505,9 +1506,8 @@ emulate_sysenter(struct x86_emulate_ctxt
 	if (c->lock_prefix)
 		return -1;
 
-	/* inject #GP if in real mode or paging is disabled */
-	if (ctxt->mode == X86EMUL_MODE_REAL ||
-		!(ctxt->vcpu->arch.cr0 & X86_CR0_PE)) {
+	/* inject #GP if in real mode */
+	if (ctxt->mode == X86EMUL_MODE_REAL) {
 		kvm_inject_gp(ctxt->vcpu, 0);
 		return -1;
 	}
@@ -1571,9 +1571,9 @@ emulate_sysexit(struct x86_emulate_ctxt
 	if (c->lock_prefix)
 		return -1;
 
-	/* inject #GP if in real mode or paging is disabled */
-	if (ctxt->mode == X86EMUL_MODE_REAL
-		|| !(ctxt->vcpu->arch.cr0 & X86_CR0_PE)) {
+	/* 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;
 	}
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2828,8 +2828,9 @@ int emulate_instruction(struct kvm_vcpu
 		vcpu->arch.emulate_ctxt.vcpu = vcpu;
 		vcpu->arch.emulate_ctxt.eflags = kvm_x86_ops->get_rflags(vcpu);
 		vcpu->arch.emulate_ctxt.mode =
+			(!(vcpu->arch.cr0 & X86_CR0_PE)) ? 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;
 


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