From: Gleb Natapov <gleb@redhat.com>
Date: Thu, 18 Mar 2010 13:20:09 +0000 (+0200)
Subject: KVM: x86 emulator: 0f (20|21|22|23) ignore mod bits.
X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=ab8557b2b361c8bb2e2421c791c8f6c4f6ba3d08;p=deliverable%2Flinux.git

KVM: x86 emulator: 0f (20|21|22|23) ignore mod bits.

Resent spec says that for 0f (20|21|22|23) the 2 bits in the mod field
are ignored. Interestingly enough older spec says that 11 is only valid
encoding.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
---

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 7c7debb424df..fa4604e03250 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2520,28 +2520,20 @@ twobyte_insn:
 		c->dst.type = OP_NONE;
 		break;
 	case 0x20: /* mov cr, reg */
-		if (c->modrm_mod != 3)
-			goto cannot_emulate;
 		c->regs[c->modrm_rm] = ops->get_cr(c->modrm_reg, ctxt->vcpu);
 		c->dst.type = OP_NONE;	/* no writeback */
 		break;
 	case 0x21: /* mov from dr to reg */
-		if (c->modrm_mod != 3)
-			goto cannot_emulate;
 		if (emulator_get_dr(ctxt, c->modrm_reg, &c->regs[c->modrm_rm]))
 			goto cannot_emulate;
 		rc = X86EMUL_CONTINUE;
 		c->dst.type = OP_NONE;	/* no writeback */
 		break;
 	case 0x22: /* mov reg, cr */
-		if (c->modrm_mod != 3)
-			goto cannot_emulate;
 		ops->set_cr(c->modrm_reg, c->modrm_val, ctxt->vcpu);
 		c->dst.type = OP_NONE;
 		break;
 	case 0x23: /* mov from reg to dr */
-		if (c->modrm_mod != 3)
-			goto cannot_emulate;
 		if (emulator_set_dr(ctxt, c->modrm_reg, c->regs[c->modrm_rm]))
 			goto cannot_emulate;
 		rc = X86EMUL_CONTINUE;