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From: Paolo Bonzini <pbonzini@redhat.com>
To: linux-kernel@vger.kernel.org,
	kvm@vger.kernel.org
Cc: seanjc@google.com,
	michael.roth@amd.com,
	aik@amd.com
Subject: [PATCH v2 07/11] KVM: x86: define standard behavior for bits 0/1 of VM type
Date: Fri, 23 Feb 2024 05:40:05 -0500
Message-Id: <20240223104009.632194-8-pbonzini@redhat.com>
In-Reply-To: <20240223104009.632194-1-pbonzini@redhat.com>
References: <20240223104009.632194-1-pbonzini@redhat.com>
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Some VM types have characteristics in common; in fact, the only use
of VM types right now is kvm_arch_has_private_mem and it assumes that
_all_ VM types have private memory.

So, let the low bits specify the characteristics of the VM type.  As
of we have two special things: whether memory is private, and whether
guest state is protected.  The latter is similar to
kvm->arch.guest_state_protected, but the latter is only set on a fully
initialized VM.  If both are set, ioctls to set registers will cause
an error---SEV-ES did not do so, which is a problematic API.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20240209183743.22030-7-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/include/asm/kvm_host.h |  9 +++-
 arch/x86/kvm/x86.c              | 93 +++++++++++++++++++++++++++------
 2 files changed, 85 insertions(+), 17 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 0bcd9ae16097..15db2697863c 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -2135,8 +2135,15 @@ void kvm_mmu_new_pgd(struct kvm_vcpu *vcpu, gpa_t new_pgd);
 void kvm_configure_mmu(bool enable_tdp, int tdp_forced_root_level,
 		       int tdp_max_root_level, int tdp_huge_page_level);
 
+
+/* Low bits of VM types provide confidential computing capabilities.  */
+#define __KVM_X86_PRIVATE_MEM_TYPE	1
+#define __KVM_X86_PROTECTED_STATE_TYPE	2
+#define __KVM_X86_VM_TYPE_FEATURES	3
+static_assert((KVM_X86_SW_PROTECTED_VM & __KVM_X86_VM_TYPE_FEATURES) == __KVM_X86_PRIVATE_MEM_TYPE);
+
 #ifdef CONFIG_KVM_PRIVATE_MEM
-#define kvm_arch_has_private_mem(kvm) ((kvm)->arch.vm_type != KVM_X86_DEFAULT_VM)
+#define kvm_arch_has_private_mem(kvm) ((kvm)->arch.vm_type & __KVM_X86_PRIVATE_MEM_TYPE)
 #else
 #define kvm_arch_has_private_mem(kvm) false
 #endif
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8746530930d5..e634e5b67516 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5526,21 +5526,30 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu,
 	return 0;
 }
 
-static void kvm_vcpu_ioctl_x86_get_debugregs(struct kvm_vcpu *vcpu,
-					     struct kvm_debugregs *dbgregs)
+static int kvm_vcpu_ioctl_x86_get_debugregs(struct kvm_vcpu *vcpu,
+					    struct kvm_debugregs *dbgregs)
 {
 	unsigned long val;
 
+	if ((vcpu->kvm->arch.vm_type & __KVM_X86_PROTECTED_STATE_TYPE) &&
+	    vcpu->arch.guest_state_protected)
+		return -EINVAL;
+
 	memset(dbgregs, 0, sizeof(*dbgregs));
 	memcpy(dbgregs->db, vcpu->arch.db, sizeof(vcpu->arch.db));
 	kvm_get_dr(vcpu, 6, &val);
 	dbgregs->dr6 = val;
 	dbgregs->dr7 = vcpu->arch.dr7;
+	return 0;
 }
 
 static int kvm_vcpu_ioctl_x86_set_debugregs(struct kvm_vcpu *vcpu,
 					    struct kvm_debugregs *dbgregs)
 {
+	if ((vcpu->kvm->arch.vm_type & __KVM_X86_PROTECTED_STATE_TYPE) &&
+	    vcpu->arch.guest_state_protected)
+		return -EINVAL;
+
 	if (dbgregs->flags)
 		return -EINVAL;
 
@@ -5559,9 +5568,13 @@ static int kvm_vcpu_ioctl_x86_set_debugregs(struct kvm_vcpu *vcpu,
 }
 
 
-static void kvm_vcpu_ioctl_x86_get_xsave2(struct kvm_vcpu *vcpu,
-					  u8 *state, unsigned int size)
+static int kvm_vcpu_ioctl_x86_get_xsave2(struct kvm_vcpu *vcpu,
+					 u8 *state, unsigned int size)
 {
+	if ((vcpu->kvm->arch.vm_type & __KVM_X86_PROTECTED_STATE_TYPE) &&
+	    fpstate_is_confidential(&vcpu->arch.guest_fpu))
+		return -EINVAL;
+
 	/*
 	 * Only copy state for features that are enabled for the guest.  The
 	 * state itself isn't problematic, but setting bits in the header for
@@ -5578,22 +5591,27 @@ static void kvm_vcpu_ioctl_x86_get_xsave2(struct kvm_vcpu *vcpu,
 			     XFEATURE_MASK_FPSSE;
 
 	if (fpstate_is_confidential(&vcpu->arch.guest_fpu))
-		return;
+		return 0;
 
 	fpu_copy_guest_fpstate_to_uabi(&vcpu->arch.guest_fpu, state, size,
 				       supported_xcr0, vcpu->arch.pkru);
+	return 0;
 }
 
-static void kvm_vcpu_ioctl_x86_get_xsave(struct kvm_vcpu *vcpu,
-					 struct kvm_xsave *guest_xsave)
+static int kvm_vcpu_ioctl_x86_get_xsave(struct kvm_vcpu *vcpu,
+					struct kvm_xsave *guest_xsave)
 {
-	kvm_vcpu_ioctl_x86_get_xsave2(vcpu, (void *)guest_xsave->region,
-				      sizeof(guest_xsave->region));
+	return kvm_vcpu_ioctl_x86_get_xsave2(vcpu, (void *)guest_xsave->region,
+					     sizeof(guest_xsave->region));
 }
 
 static int kvm_vcpu_ioctl_x86_set_xsave(struct kvm_vcpu *vcpu,
 					struct kvm_xsave *guest_xsave)
 {
+	if ((vcpu->kvm->arch.vm_type & __KVM_X86_PROTECTED_STATE_TYPE) &&
+	    fpstate_is_confidential(&vcpu->arch.guest_fpu))
+		return -EINVAL;
+
 	if (fpstate_is_confidential(&vcpu->arch.guest_fpu))
 		return 0;
 
@@ -5603,18 +5621,23 @@ static int kvm_vcpu_ioctl_x86_set_xsave(struct kvm_vcpu *vcpu,
 					      &vcpu->arch.pkru);
 }
 
-static void kvm_vcpu_ioctl_x86_get_xcrs(struct kvm_vcpu *vcpu,
-					struct kvm_xcrs *guest_xcrs)
+static int kvm_vcpu_ioctl_x86_get_xcrs(struct kvm_vcpu *vcpu,
+				       struct kvm_xcrs *guest_xcrs)
 {
+	if ((vcpu->kvm->arch.vm_type & __KVM_X86_PROTECTED_STATE_TYPE) &&
+	    vcpu->arch.guest_state_protected)
+		return -EINVAL;
+
 	if (!boot_cpu_has(X86_FEATURE_XSAVE)) {
 		guest_xcrs->nr_xcrs = 0;
-		return;
+		return 0;
 	}
 
 	guest_xcrs->nr_xcrs = 1;
 	guest_xcrs->flags = 0;
 	guest_xcrs->xcrs[0].xcr = XCR_XFEATURE_ENABLED_MASK;
 	guest_xcrs->xcrs[0].value = vcpu->arch.xcr0;
+	return 0;
 }
 
 static int kvm_vcpu_ioctl_x86_set_xcrs(struct kvm_vcpu *vcpu,
@@ -5622,6 +5645,10 @@ static int kvm_vcpu_ioctl_x86_set_xcrs(struct kvm_vcpu *vcpu,
 {
 	int i, r = 0;
 
+	if ((vcpu->kvm->arch.vm_type & __KVM_X86_PROTECTED_STATE_TYPE) &&
+	    vcpu->arch.guest_state_protected)
+		return -EINVAL;
+
 	if (!boot_cpu_has(X86_FEATURE_XSAVE))
 		return -EINVAL;
 
@@ -6010,7 +6037,9 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 	case KVM_GET_DEBUGREGS: {
 		struct kvm_debugregs dbgregs;
 
-		kvm_vcpu_ioctl_x86_get_debugregs(vcpu, &dbgregs);
+		r = kvm_vcpu_ioctl_x86_get_debugregs(vcpu, &dbgregs);
+		if (r < 0)
+			break;
 
 		r = -EFAULT;
 		if (copy_to_user(argp, &dbgregs,
@@ -6040,7 +6069,9 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 		if (!u.xsave)
 			break;
 
-		kvm_vcpu_ioctl_x86_get_xsave(vcpu, u.xsave);
+		r = kvm_vcpu_ioctl_x86_get_xsave(vcpu, u.xsave);
+		if (r < 0)
+			break;
 
 		r = -EFAULT;
 		if (copy_to_user(argp, u.xsave, sizeof(struct kvm_xsave)))
@@ -6069,7 +6100,9 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 		if (!u.xsave)
 			break;
 
-		kvm_vcpu_ioctl_x86_get_xsave2(vcpu, u.buffer, size);
+		r = kvm_vcpu_ioctl_x86_get_xsave2(vcpu, u.buffer, size);
+		if (r < 0)
+			break;
 
 		r = -EFAULT;
 		if (copy_to_user(argp, u.xsave, size))
@@ -6085,7 +6118,9 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 		if (!u.xcrs)
 			break;
 
-		kvm_vcpu_ioctl_x86_get_xcrs(vcpu, u.xcrs);
+		r = kvm_vcpu_ioctl_x86_get_xcrs(vcpu, u.xcrs);
+		if (r < 0)
+			break;
 
 		r = -EFAULT;
 		if (copy_to_user(argp, u.xcrs,
@@ -6229,6 +6264,11 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 	}
 #endif
 	case KVM_GET_SREGS2: {
+		r = -EINVAL;
+		if ((vcpu->kvm->arch.vm_type & __KVM_X86_PROTECTED_STATE_TYPE) &&
+		    vcpu->arch.guest_state_protected)
+			goto out;
+
 		u.sregs2 = kzalloc(sizeof(struct kvm_sregs2), GFP_KERNEL);
 		r = -ENOMEM;
 		if (!u.sregs2)
@@ -6241,6 +6281,11 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 		break;
 	}
 	case KVM_SET_SREGS2: {
+		r = -EINVAL;
+		if ((vcpu->kvm->arch.vm_type & __KVM_X86_PROTECTED_STATE_TYPE) &&
+		    vcpu->arch.guest_state_protected)
+			goto out;
+
 		u.sregs2 = memdup_user(argp, sizeof(struct kvm_sregs2));
 		if (IS_ERR(u.sregs2)) {
 			r = PTR_ERR(u.sregs2);
@@ -11466,6 +11511,10 @@ static void __get_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs)
 
 int kvm_arch_vcpu_ioctl_get_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs)
 {
+	if ((vcpu->kvm->arch.vm_type & __KVM_X86_PROTECTED_STATE_TYPE) &&
+	    vcpu->arch.guest_state_protected)
+		return -EINVAL;
+
 	vcpu_load(vcpu);
 	__get_regs(vcpu, regs);
 	vcpu_put(vcpu);
@@ -11507,6 +11556,10 @@ static void __set_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs)
 
 int kvm_arch_vcpu_ioctl_set_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs)
 {
+	if ((vcpu->kvm->arch.vm_type & __KVM_X86_PROTECTED_STATE_TYPE) &&
+	    vcpu->arch.guest_state_protected)
+		return -EINVAL;
+
 	vcpu_load(vcpu);
 	__set_regs(vcpu, regs);
 	vcpu_put(vcpu);
@@ -11579,6 +11632,10 @@ static void __get_sregs2(struct kvm_vcpu *vcpu, struct kvm_sregs2 *sregs2)
 int kvm_arch_vcpu_ioctl_get_sregs(struct kvm_vcpu *vcpu,
 				  struct kvm_sregs *sregs)
 {
+	if ((vcpu->kvm->arch.vm_type & __KVM_X86_PROTECTED_STATE_TYPE) &&
+	    vcpu->arch.guest_state_protected)
+		return -EINVAL;
+
 	vcpu_load(vcpu);
 	__get_sregs(vcpu, sregs);
 	vcpu_put(vcpu);
@@ -11846,6 +11903,10 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu,
 {
 	int ret;
 
+	if ((vcpu->kvm->arch.vm_type & __KVM_X86_PROTECTED_STATE_TYPE) &&
+	    vcpu->arch.guest_state_protected)
+		return -EINVAL;
+
 	vcpu_load(vcpu);
 	ret = __set_sregs(vcpu, sregs);
 	vcpu_put(vcpu);
-- 
2.39.1