[PATCH v2 0/2] KVM: x86: cleanups for MOV from/to DR

[PATCH v2 0/2] KVM: x86: cleanups for MOV from/to DR

[Paolo Bonzini]

This is the new version of the "KVM: x86: move kvm_inject_gp up from
kvm_set_dr to callers" patch.

Paolo Bonzini (2):
  KVM: x86: reading DR cannot fail
  KVM: x86: move kvm_inject_gp up from kvm_set_dr to callers

 arch/x86/include/asm/kvm_host.h |  2 +-
 arch/x86/kvm/kvm_emulate.h      |  2 +-
 arch/x86/kvm/svm/svm.c          | 13 +++++--------
 arch/x86/kvm/vmx/vmx.c          | 20 +++++++++++---------
 arch/x86/kvm/x86.c              | 28 +++++++++-------------------
 5 files changed, 27 insertions(+), 38 deletions(-)

-- 
2.26.2

[PATCH v2 1/2] KVM: x86: reading debug registers cannot fail

[Paolo Bonzini]

kvm_get_dr and emulator_get_dr accept an in-range value for the register
number so they cannot fail.  Change the return type to void.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/include/asm/kvm_host.h | 2 +-
 arch/x86/kvm/kvm_emulate.h      | 2 +-
 arch/x86/kvm/vmx/vmx.c          | 3 +--
 arch/x86/kvm/x86.c              | 9 ++++-----
 4 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 717940e97f66..c6215f62a0f6 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1560,7 +1560,7 @@ int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3);
 int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4);
 int kvm_set_cr8(struct kvm_vcpu *vcpu, unsigned long cr8);
 int kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val);
-int kvm_get_dr(struct kvm_vcpu *vcpu, int dr, unsigned long *val);
+void kvm_get_dr(struct kvm_vcpu *vcpu, int dr, unsigned long *val);
 unsigned long kvm_get_cr8(struct kvm_vcpu *vcpu);
 void kvm_lmsw(struct kvm_vcpu *vcpu, unsigned long msw);
 void kvm_get_cs_db_l_bits(struct kvm_vcpu *vcpu, int *db, int *l);
diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h
index 43c93ffa76ed..0d359115429a 100644
--- a/arch/x86/kvm/kvm_emulate.h
+++ b/arch/x86/kvm/kvm_emulate.h
@@ -205,7 +205,7 @@ struct x86_emulate_ops {
 	ulong (*get_cr)(struct x86_emulate_ctxt *ctxt, int cr);
 	int (*set_cr)(struct x86_emulate_ctxt *ctxt, int cr, ulong val);
 	int (*cpl)(struct x86_emulate_ctxt *ctxt);
-	int (*get_dr)(struct x86_emulate_ctxt *ctxt, int dr, ulong *dest);
+	void (*get_dr)(struct x86_emulate_ctxt *ctxt, int dr, ulong *dest);
 	int (*set_dr)(struct x86_emulate_ctxt *ctxt, int dr, ulong value);
 	u64 (*get_smbase)(struct x86_emulate_ctxt *ctxt);
 	void (*set_smbase)(struct x86_emulate_ctxt *ctxt, u64 smbase);
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 777177ea9a35..049fbbd0aa1a 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5142,8 +5142,7 @@ static int handle_dr(struct kvm_vcpu *vcpu)
 	if (exit_qualification & TYPE_MOV_FROM_DR) {
 		unsigned long val;
 
-		if (kvm_get_dr(vcpu, dr, &val))
-			return 1;
+		kvm_get_dr(vcpu, dr, &val);
 		kvm_register_write(vcpu, reg, val);
 	} else
 		if (kvm_set_dr(vcpu, dr, kvm_register_readl(vcpu, reg)))
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d9f931c63293..dcb67429b75d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1181,7 +1181,7 @@ int kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val)
 }
 EXPORT_SYMBOL_GPL(kvm_set_dr);
 
-int kvm_get_dr(struct kvm_vcpu *vcpu, int dr, unsigned long *val)
+void kvm_get_dr(struct kvm_vcpu *vcpu, int dr, unsigned long *val)
 {
 	size_t size = ARRAY_SIZE(vcpu->arch.db);
 
@@ -1198,7 +1198,6 @@ int kvm_get_dr(struct kvm_vcpu *vcpu, int dr, unsigned long *val)
 		*val = vcpu->arch.dr7;
 		break;
 	}
-	return 0;
 }
 EXPORT_SYMBOL_GPL(kvm_get_dr);
 
@@ -6610,10 +6609,10 @@ static void emulator_wbinvd(struct x86_emulate_ctxt *ctxt)
 	kvm_emulate_wbinvd_noskip(emul_to_vcpu(ctxt));
 }
 
-static int emulator_get_dr(struct x86_emulate_ctxt *ctxt, int dr,
-			   unsigned long *dest)
+static void emulator_get_dr(struct x86_emulate_ctxt *ctxt, int dr,
+			    unsigned long *dest)
 {
-	return kvm_get_dr(emul_to_vcpu(ctxt), dr, dest);
+	kvm_get_dr(emul_to_vcpu(ctxt), dr, dest);
 }
 
 static int emulator_set_dr(struct x86_emulate_ctxt *ctxt, int dr,
-- 
2.26.2

[PATCH v2 2/2] KVM: x86: move kvm_inject_gp up from kvm_set_dr to callers

[Paolo Bonzini]

Push the injection of #GP up to the callers, since they can just use
kvm_complete_insn_gp and __kvm_set_dr pretty much returns what the
callers can pass to kvm_complete_insn_gp.

Therefore, rename __kvm_set_dr to kvm_set_dr and drop the kvm_set_dr
wrapper.  This also allows nested VMX code, which really wanted to use
__kvm_set_dr, to use the right function.

While at it, remove the kvm_require_dr() check from the SVM handler.
The APM states:

  All normal exception checks take precedence over the SVM intercepts.

and that includes the CR4.DE=1 #UD.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/kvm/svm/svm.c | 13 +++++--------
 arch/x86/kvm/vmx/vmx.c | 17 ++++++++++-------
 arch/x86/kvm/x86.c     | 19 +++++--------------
 3 files changed, 20 insertions(+), 29 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 4141caea857a..ea1bd96a9804 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2619,6 +2619,7 @@ static int dr_interception(struct vcpu_svm *svm)
 {
 	int reg, dr;
 	unsigned long val;
+	int err = 0;
 
 	if (svm->vcpu.guest_debug == 0) {
 		/*
@@ -2636,20 +2637,16 @@ static int dr_interception(struct vcpu_svm *svm)
 
 	reg = svm->vmcb->control.exit_info_1 & SVM_EXITINFO_REG_MASK;
 	dr = svm->vmcb->control.exit_code - SVM_EXIT_READ_DR0;
-
 	if (dr >= 16) { /* mov to DRn */
-		if (!kvm_require_dr(&svm->vcpu, dr - 16))
-			return 1;
+		dr -= 16;
 		val = kvm_register_read(&svm->vcpu, reg);
-		kvm_set_dr(&svm->vcpu, dr - 16, val);
+		err = kvm_set_dr(&svm->vcpu, dr, val);
 	} else {
-		if (!kvm_require_dr(&svm->vcpu, dr))
-			return 1;
 		kvm_get_dr(&svm->vcpu, dr, &val);
 		kvm_register_write(&svm->vcpu, reg, val);
 	}
 
-	return kvm_skip_emulated_instruction(&svm->vcpu);
+	return kvm_complete_insn_gp(&svm->vcpu, err);
 }
 
 static int cr8_write_interception(struct vcpu_svm *svm)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 049fbbd0aa1a..13898871e5b0 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5095,6 +5095,7 @@ static int handle_dr(struct kvm_vcpu *vcpu)
 {
 	unsigned long exit_qualification;
 	int dr, dr7, reg;
+	int err = 1;
 
 	exit_qualification = vmx_get_exit_qual(vcpu);
 	dr = exit_qualification & DEBUG_REG_ACCESS_NUM;
@@ -5103,9 +5104,9 @@ static int handle_dr(struct kvm_vcpu *vcpu)
 	if (!kvm_require_dr(vcpu, dr))
 		return 1;
 
-	/* Do not handle if the CPL > 0, will trigger GP on re-entry */
-	if (!kvm_require_cpl(vcpu, 0))
-		return 1;
+	if (kvm_x86_ops.get_cpl(vcpu) > 0)
+		goto out;
+
 	dr7 = vmcs_readl(GUEST_DR7);
 	if (dr7 & DR7_GD) {
 		/*
@@ -5144,11 +5145,13 @@ static int handle_dr(struct kvm_vcpu *vcpu)
 
 		kvm_get_dr(vcpu, dr, &val);
 		kvm_register_write(vcpu, reg, val);
-	} else
-		if (kvm_set_dr(vcpu, dr, kvm_register_readl(vcpu, reg)))
-			return 1;
+		err = 0;
+	} else {
+		err = kvm_set_dr(vcpu, dr, kvm_register_readl(vcpu, reg));
+	}
 
-	return kvm_skip_emulated_instruction(vcpu);
+out:
+	return kvm_complete_insn_gp(vcpu, err);
 }
 
 static void vmx_sync_dirty_debug_regs(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index dcb67429b75d..baa90ae76ba5 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1143,7 +1143,7 @@ static u64 kvm_dr6_fixed(struct kvm_vcpu *vcpu)
 	return fixed;
 }
 
-static int __kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val)
+int kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val)
 {
 	size_t size = ARRAY_SIZE(vcpu->arch.db);
 
@@ -1156,13 +1156,13 @@ static int __kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val)
 	case 4:
 	case 6:
 		if (!kvm_dr6_valid(val))
-			return -1; /* #GP */
+			return 1; /* #GP */
 		vcpu->arch.dr6 = (val & DR6_VOLATILE) | kvm_dr6_fixed(vcpu);
 		break;
 	case 5:
 	default: /* 7 */
 		if (!kvm_dr7_valid(val))
-			return -1; /* #GP */
+			return 1; /* #GP */
 		vcpu->arch.dr7 = (val & DR7_VOLATILE) | DR7_FIXED_1;
 		kvm_update_dr7(vcpu);
 		break;
@@ -1170,15 +1170,6 @@ static int __kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val)
 
 	return 0;
 }
-
-int kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val)
-{
-	if (__kvm_set_dr(vcpu, dr, val)) {
-		kvm_inject_gp(vcpu, 0);
-		return 1;
-	}
-	return 0;
-}
 EXPORT_SYMBOL_GPL(kvm_set_dr);
 
 void kvm_get_dr(struct kvm_vcpu *vcpu, int dr, unsigned long *val)
@@ -6619,7 +6610,7 @@ static int emulator_set_dr(struct x86_emulate_ctxt *ctxt, int dr,
 			   unsigned long value)
 {
 
-	return __kvm_set_dr(emul_to_vcpu(ctxt), dr, value);
+	return kvm_set_dr(emul_to_vcpu(ctxt), dr, value);
 }
 
 static u64 mk_cr_64(u64 curr_cr, u32 new_val)
@@ -8664,7 +8655,7 @@ static void enter_smm(struct kvm_vcpu *vcpu)
 	dt.address = dt.size = 0;
 	static_call(kvm_x86_set_idt)(vcpu, &dt);
 
-	__kvm_set_dr(vcpu, 7, DR7_FIXED_1);
+	kvm_set_dr(vcpu, 7, DR7_FIXED_1);
 
 	cs.selector = (vcpu->arch.smbase >> 4) & 0xffff;
 	cs.base = vcpu->arch.smbase;
-- 
2.26.2