linux-kernel - [PATCH v3 05/22] kvm: x86: Check permitted dynamic xfeatures at KVM_SET

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Date:   Wed, 22 Dec 2021 04:40:35 -0800
From:   Jing Liu <jing2.liu@...el.com>
To:     x86@...nel.org, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, pbonzini@...hat.com, corbet@....net,
        shuah@...nel.org
Cc:     seanjc@...gle.com, jun.nakajima@...el.com, kevin.tian@...el.com,
        jing2.liu@...ux.intel.com, jing2.liu@...el.com,
        guang.zeng@...el.com, wei.w.wang@...el.com, yang.zhong@...el.com
Subject: [PATCH v3 05/22] kvm: x86: Check permitted dynamic xfeatures at KVM_SET_CPUID2

Guest xstate permissions should be set by userspace VMM before vcpu
creation. Extend KVM_SET_CPUID2 to verify that every feature reported
in CPUID[0xD] has proper permission set.

Signed-off-by: Jing Liu <jing2.liu@...el.com>
---
 arch/x86/kvm/cpuid.c | 36 ++++++++++++++++++++++++------------
 1 file changed, 24 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 4855344091b8..a068373a7fbd 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -81,7 +81,9 @@ static inline struct kvm_cpuid_entry2 *cpuid_entry2_find(
 	return NULL;
 }
 
-static int kvm_check_cpuid(struct kvm_cpuid_entry2 *entries, int nent)
+static int kvm_check_cpuid(struct kvm_vcpu *vcpu,
+			   struct kvm_cpuid_entry2 *entries,
+			   int nent)
 {
 	struct kvm_cpuid_entry2 *best;
 
@@ -97,6 +99,16 @@ static int kvm_check_cpuid(struct kvm_cpuid_entry2 *entries, int nent)
 			return -EINVAL;
 	}
 
+	/* Check guest permissions for dynamically-enabled xfeatures */
+	best = cpuid_entry2_find(entries, nent, 0xd, 0);
+	if (best) {
+		u64 xfeatures;
+
+		xfeatures = best->eax | ((u64)best->edx << 32);
+		if (xfeatures & ~vcpu->arch.guest_fpu.perm)
+			return -ENXIO;
+	}
+
 	return 0;
 }
 
@@ -277,21 +289,21 @@ u64 kvm_vcpu_reserved_gpa_bits_raw(struct kvm_vcpu *vcpu)
 static int kvm_set_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2 *e2,
                         int nent)
 {
-    int r;
+	int r;
 
-    r = kvm_check_cpuid(e2, nent);
-    if (r)
-        return r;
+	r = kvm_check_cpuid(vcpu, e2, nent);
+	if (r)
+		return r;
 
-    kvfree(vcpu->arch.cpuid_entries);
-    vcpu->arch.cpuid_entries = e2;
-    vcpu->arch.cpuid_nent = nent;
+	kvfree(vcpu->arch.cpuid_entries);
+	vcpu->arch.cpuid_entries = e2;
+	vcpu->arch.cpuid_nent = nent;
 
-    kvm_update_kvm_cpuid_base(vcpu);
-    kvm_update_cpuid_runtime(vcpu);
-    kvm_vcpu_after_set_cpuid(vcpu);
+	kvm_update_kvm_cpuid_base(vcpu);
+	kvm_update_cpuid_runtime(vcpu);
+	kvm_vcpu_after_set_cpuid(vcpu);
 
-    return 0;
+	return 0;
 }
 
 /* when an old userspace process fills a new kernel module */
-- 
2.27.0