linux-kernel - [PATCH v7 08/26] KVM: x86: Rework cpuid_get_supported

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Message-Id: <20231124055330.138870-9-weijiang.yang@intel.com>
Date:   Fri, 24 Nov 2023 00:53:12 -0500
From:   Yang Weijiang <weijiang.yang@...el.com>
To:     seanjc@...gle.com, pbonzini@...hat.com, dave.hansen@...el.com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     peterz@...radead.org, chao.gao@...el.com,
        rick.p.edgecombe@...el.com, mlevitsk@...hat.com,
        john.allen@....com, weijiang.yang@...el.com
Subject: [PATCH v7 08/26] KVM: x86: Rework cpuid_get_supported_xcr0() to operate on vCPU data

From: Sean Christopherson <seanjc@...gle.com>

Rework and rename cpuid_get_supported_xcr0() to explicitly operate on
vCPU state, i.e. on a vCPU's CPUID state, now that the only usage of
the helper is to retrieve a vCPU's already-set CPUID.

Prior to commit 275a87244ec8 ("KVM: x86: Don't adjust guest's CPUID.0x12.1
(allowed SGX enclave XFRM)"), KVM incorrectly fudged guest CPUID at runtime,
which in turn necessitated massaging the incoming CPUID state for
KVM_SET_CPUID{2} so as not to run afoul of kvm_cpuid_check_equal().
I.e. KVM also invoked cpuid_get_supported_xcr0() with the incoming CPUID
state, and thus without an explicit vCPU object.

Opportunistically move the helper below kvm_update_cpuid_runtime() to make
it harder to repeat the mistake of querying supported XCR0 for runtime
updates.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
---
 arch/x86/kvm/cpuid.c | 33 ++++++++++++++++-----------------
 1 file changed, 16 insertions(+), 17 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index dda6fc4cfae8..d0315e469d92 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -247,21 +247,6 @@ void kvm_update_pv_runtime(struct kvm_vcpu *vcpu)
 		vcpu->arch.pv_cpuid.features = best->eax;
 }
 
-/*
- * Calculate guest's supported XCR0 taking into account guest CPUID data and
- * KVM's supported XCR0 (comprised of host's XCR0 and KVM_SUPPORTED_XCR0).
- */
-static u64 cpuid_get_supported_xcr0(struct kvm_cpuid_entry2 *entries, int nent)
-{
-	struct kvm_cpuid_entry2 *best;
-
-	best = cpuid_entry2_find(entries, nent, 0xd, 0);
-	if (!best)
-		return 0;
-
-	return (best->eax | ((u64)best->edx << 32)) & kvm_caps.supported_xcr0;
-}
-
 static void __kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2 *entries,
 				       int nent)
 {
@@ -312,6 +297,21 @@ void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu)
 }
 EXPORT_SYMBOL_GPL(kvm_update_cpuid_runtime);
 
+/*
+ * Calculate guest's supported XCR0 taking into account guest CPUID data and
+ * KVM's supported XCR0 (comprised of host's XCR0 and KVM_SUPPORTED_XCR0).
+ */
+static u64 vcpu_get_supported_xcr0(struct kvm_vcpu *vcpu)
+{
+	struct kvm_cpuid_entry2 *best;
+
+	best = kvm_find_cpuid_entry_index(vcpu, 0xd, 0);
+	if (!best)
+		return 0;
+
+	return (best->eax | ((u64)best->edx << 32)) & kvm_caps.supported_xcr0;
+}
+
 static bool kvm_cpuid_has_hyperv(struct kvm_cpuid_entry2 *entries, int nent)
 {
 	struct kvm_cpuid_entry2 *entry;
@@ -357,8 +357,7 @@ static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
 		kvm_apic_set_version(vcpu);
 	}
 
-	vcpu->arch.guest_supported_xcr0 =
-		cpuid_get_supported_xcr0(vcpu->arch.cpuid_entries, vcpu->arch.cpuid_nent);
+	vcpu->arch.guest_supported_xcr0 = vcpu_get_supported_xcr0(vcpu);
 
 	kvm_update_pv_runtime(vcpu);
 
-- 
2.27.0