[PATCH v9 08/27] KVM: x86: Rework cpuid_get_supported_xcr0() to operate on vCPU data

Yang Weijiang
2024-01-24T02:42:37Z

From: Sean Christopherson <seanjc@google.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@google.com>
Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.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 294e5bd5f8a0..624954203b40 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)
{
#ifdef CONFIG_KVM_HYPERV
@@ -361,8 +361,7 @@ 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);

--
2.39.3