KVM: SVM: Add intercept check for emulated cr accesses

This patch adds all necessary intercept checks for
instructions that access the crX registers.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/include/asm/kvm_emulate.h

@@ -304,6 +304,9 @@ enum x86_intercept_stage {
 
 enum x86_intercept {
 	x86_intercept_none,
+	x86_intercept_cr_read,
+	x86_intercept_cr_write,
+	x86_intercept_clts,
 	x86_intercept_lmsw,
 	x86_intercept_smsw,
 	x86_intercept_lidt,

arch/x86/include/asm/kvm_host.h

@@ -35,10 +35,25 @@
 #define KVM_PIO_PAGE_OFFSET 1
 #define KVM_COALESCED_MMIO_PAGE_OFFSET 2
 
+#define CR0_RESERVED_BITS                                               \
+	(~(unsigned long)(X86_CR0_PE | X86_CR0_MP | X86_CR0_EM | X86_CR0_TS \
+			  | X86_CR0_ET | X86_CR0_NE | X86_CR0_WP | X86_CR0_AM \
+			  | X86_CR0_NW | X86_CR0_CD | X86_CR0_PG))
+
 #define CR3_PAE_RESERVED_BITS ((X86_CR3_PWT | X86_CR3_PCD) - 1)
 #define CR3_NONPAE_RESERVED_BITS ((PAGE_SIZE-1) & ~(X86_CR3_PWT | X86_CR3_PCD))
 #define CR3_L_MODE_RESERVED_BITS (CR3_NONPAE_RESERVED_BITS |	\
 				  0xFFFFFF0000000000ULL)
+#define CR4_RESERVED_BITS                                               \
+	(~(unsigned long)(X86_CR4_VME | X86_CR4_PVI | X86_CR4_TSD | X86_CR4_DE\
+			  | X86_CR4_PSE | X86_CR4_PAE | X86_CR4_MCE     \
+			  | X86_CR4_PGE | X86_CR4_PCE | X86_CR4_OSFXSR  \
+			  | X86_CR4_OSXSAVE \
+			  | X86_CR4_OSXMMEXCPT | X86_CR4_VMXE))
+
+#define CR8_RESERVED_BITS (~(unsigned long)X86_CR8_TPR)
+
+
 
 #define INVALID_PAGE (~(hpa_t)0)
 #define VALID_PAGE(x) ((x) != INVALID_PAGE)

arch/x86/kvm/emulate.c

@@ -2445,6 +2445,95 @@ static int em_movdqu(struct x86_emulate_ctxt *ctxt)
 	return X86EMUL_CONTINUE;
 }
 
+static bool valid_cr(int nr)
+{
+	switch (nr) {
+	case 0:
+	case 2 ... 4:
+	case 8:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static int check_cr_read(struct x86_emulate_ctxt *ctxt)
+{
+	struct decode_cache *c = &ctxt->decode;
+
+	if (!valid_cr(c->modrm_reg))
+		return emulate_ud(ctxt);
+
+	return X86EMUL_CONTINUE;
+}
+
+static int check_cr_write(struct x86_emulate_ctxt *ctxt)
+{
+	struct decode_cache *c = &ctxt->decode;
+	u64 new_val = c->src.val64;
+	int cr = c->modrm_reg;
+
+	static u64 cr_reserved_bits[] = {
+		0xffffffff00000000ULL,
+		0, 0, 0, /* CR3 checked later */
+		CR4_RESERVED_BITS,
+		0, 0, 0,
+		CR8_RESERVED_BITS,
+	};
+
+	if (!valid_cr(cr))
+		return emulate_ud(ctxt);
+
+	if (new_val & cr_reserved_bits[cr])
+		return emulate_gp(ctxt, 0);
+
+	switch (cr) {
+	case 0: {
+		u64 cr4, efer;
+		if (((new_val & X86_CR0_PG) && !(new_val & X86_CR0_PE)) ||
+		    ((new_val & X86_CR0_NW) && !(new_val & X86_CR0_CD)))
+			return emulate_gp(ctxt, 0);
+
+		cr4 = ctxt->ops->get_cr(4, ctxt->vcpu);
+		ctxt->ops->get_msr(ctxt->vcpu, MSR_EFER, &efer);
+
+		if ((new_val & X86_CR0_PG) && (efer & EFER_LME) &&
+		    !(cr4 & X86_CR4_PAE))
+			return emulate_gp(ctxt, 0);
+
+		break;
+		}
+	case 3: {
+		u64 rsvd = 0;
+
+		if (is_long_mode(ctxt->vcpu))
+			rsvd = CR3_L_MODE_RESERVED_BITS;
+		else if (is_pae(ctxt->vcpu))
+			rsvd = CR3_PAE_RESERVED_BITS;
+		else if (is_paging(ctxt->vcpu))
+			rsvd = CR3_NONPAE_RESERVED_BITS;
+
+		if (new_val & rsvd)
+			return emulate_gp(ctxt, 0);
+
+		break;
+		}
+	case 4: {
+		u64 cr4, efer;
+
+		cr4 = ctxt->ops->get_cr(4, ctxt->vcpu);
+		ctxt->ops->get_msr(ctxt->vcpu, MSR_EFER, &efer);
+
+		if ((efer & EFER_LMA) && !(new_val & X86_CR4_PAE))
+			return emulate_gp(ctxt, 0);
+
+		break;
+		}
+	}
+
+	return X86EMUL_CONTINUE;
+}
+
 #define D(_y) { .flags = (_y) }
 #define DI(_y, _i) { .flags = (_y), .intercept = x86_intercept_##_i }
 #define DIP(_y, _i, _p) { .flags = (_y), .intercept = x86_intercept_##_i, \
@@ -2632,14 +2721,16 @@ static struct opcode opcode_table[256] = {
 static struct opcode twobyte_table[256] = {
 	/* 0x00 - 0x0F */
 	N, GD(0, &group7), N, N,
-	N, D(ImplicitOps | VendorSpecific), D(ImplicitOps | Priv), N,
+	N, D(ImplicitOps | VendorSpecific), DI(ImplicitOps | Priv, clts), N,
 	DI(ImplicitOps | Priv, invd), DI(ImplicitOps | Priv, wbinvd), N, N,
 	N, D(ImplicitOps | ModRM), N, N,
 	/* 0x10 - 0x1F */
 	N, N, N, N, N, N, N, N, D(ImplicitOps | ModRM), N, N, N, N, N, N, N,
 	/* 0x20 - 0x2F */
-	D(ModRM | DstMem | Priv | Op3264), D(ModRM | DstMem | Priv | Op3264),
-	D(ModRM | SrcMem | Priv | Op3264), D(ModRM | SrcMem | Priv | Op3264),
+	DIP(ModRM | DstMem | Priv | Op3264, cr_read, check_cr_read),
+	D(ModRM | DstMem | Priv | Op3264),
+	DIP(ModRM | SrcMem | Priv | Op3264, cr_write, check_cr_write),
+	D(ModRM | SrcMem | Priv | Op3264),
 	N, N, N, N,
 	N, N, N, N, N, N, N, N,
 	/* 0x30 - 0x3F */
@@ -3724,14 +3815,6 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
 	case 0x18:		/* Grp16 (prefetch/nop) */
 		break;
 	case 0x20: /* mov cr, reg */
-		switch (c->modrm_reg) {
-		case 1:
-		case 5 ... 7:
-		case 9 ... 15:
-			emulate_ud(ctxt);
-			rc = X86EMUL_PROPAGATE_FAULT;
-			goto done;
-		}
 		c->dst.val = ops->get_cr(c->modrm_reg, ctxt->vcpu);
 		break;
 	case 0x21: /* mov from dr to reg */

arch/x86/kvm/svm.c

@@ -3868,11 +3868,90 @@ static void svm_fpu_deactivate(struct kvm_vcpu *vcpu)
 	update_cr0_intercept(svm);
 }
 
+#define POST_EX(exit) { .exit_code = (exit), \
+			.stage = X86_ICPT_POST_EXCEPT, \
+			.valid = true }
+
+static struct __x86_intercept {
+	u32 exit_code;
+	enum x86_intercept_stage stage;
+	bool valid;
+} x86_intercept_map[] = {
+	[x86_intercept_cr_read]		= POST_EX(SVM_EXIT_READ_CR0),
+	[x86_intercept_cr_write]	= POST_EX(SVM_EXIT_WRITE_CR0),
+	[x86_intercept_clts]		= POST_EX(SVM_EXIT_WRITE_CR0),
+	[x86_intercept_lmsw]		= POST_EX(SVM_EXIT_WRITE_CR0),
+	[x86_intercept_smsw]		= POST_EX(SVM_EXIT_READ_CR0),
+};
+
+#undef POST_EX
+
 static int svm_check_intercept(struct kvm_vcpu *vcpu,
 			       struct x86_instruction_info *info,
 			       enum x86_intercept_stage stage)
 {
-	return X86EMUL_CONTINUE;
+	struct vcpu_svm *svm = to_svm(vcpu);
+	int vmexit, ret = X86EMUL_CONTINUE;
+	struct __x86_intercept icpt_info;
+	struct vmcb *vmcb = svm->vmcb;
+
+	if (info->intercept >= ARRAY_SIZE(x86_intercept_map))
+		goto out;
+
+	icpt_info = x86_intercept_map[info->intercept];
+
+	if (!icpt_info.valid || stage != icpt_info.stage)
+		goto out;
+
+	switch (icpt_info.exit_code) {
+	case SVM_EXIT_READ_CR0:
+		if (info->intercept == x86_intercept_cr_read)
+			icpt_info.exit_code += info->modrm_reg;
+		break;
+	case SVM_EXIT_WRITE_CR0: {
+		unsigned long cr0, val;
+		u64 intercept;
+
+		if (info->intercept == x86_intercept_cr_write)
+			icpt_info.exit_code += info->modrm_reg;
+
+		if (icpt_info.exit_code != SVM_EXIT_WRITE_CR0)
+			break;
+
+		intercept = svm->nested.intercept;
+
+		if (!(intercept & (1ULL << INTERCEPT_SELECTIVE_CR0)))
+			break;
+
+		cr0 = vcpu->arch.cr0 & ~SVM_CR0_SELECTIVE_MASK;
+		val = info->src_val  & ~SVM_CR0_SELECTIVE_MASK;
+
+		if (info->intercept == x86_intercept_lmsw) {
+			cr0 &= 0xfUL;
+			val &= 0xfUL;
+			/* lmsw can't clear PE - catch this here */
+			if (cr0 & X86_CR0_PE)
+				val |= X86_CR0_PE;
+		}
+
+		if (cr0 ^ val)
+			icpt_info.exit_code = SVM_EXIT_CR0_SEL_WRITE;
+
+		break;
+	}
+	default:
+		break;
+	}
+
+	vmcb->control.next_rip  = info->next_rip;
+	vmcb->control.exit_code = icpt_info.exit_code;
+	vmexit = nested_svm_exit_handled(svm);
+
+	ret = (vmexit == NESTED_EXIT_DONE) ? X86EMUL_INTERCEPTED
+					   : X86EMUL_CONTINUE;
+
+out:
+	return ret;
 }
 
 static struct kvm_x86_ops svm_x86_ops = {

arch/x86/kvm/x86.c

@@ -60,19 +60,6 @@
 #include <asm/div64.h>
 
 #define MAX_IO_MSRS 256
-#define CR0_RESERVED_BITS						\
-	(~(unsigned long)(X86_CR0_PE | X86_CR0_MP | X86_CR0_EM | X86_CR0_TS \
-			  | X86_CR0_ET | X86_CR0_NE | X86_CR0_WP | X86_CR0_AM \
-			  | X86_CR0_NW | X86_CR0_CD | X86_CR0_PG))
-#define CR4_RESERVED_BITS						\
-	(~(unsigned long)(X86_CR4_VME | X86_CR4_PVI | X86_CR4_TSD | X86_CR4_DE\
-			  | X86_CR4_PSE | X86_CR4_PAE | X86_CR4_MCE	\
-			  | X86_CR4_PGE | X86_CR4_PCE | X86_CR4_OSFXSR	\
-			  | X86_CR4_OSXSAVE \
-			  | X86_CR4_OSXMMEXCPT | X86_CR4_VMXE))
-
-#define CR8_RESERVED_BITS (~(unsigned long)X86_CR8_TPR)
-
 #define KVM_MAX_MCE_BANKS 32
 #define KVM_MCE_CAP_SUPPORTED (MCG_CTL_P | MCG_SER_P)