[RFC PATCH 13/27] KVM: x86: Add a helper to initialize CPUID multi-bit fields

[Binbin Wu <binbin.wu@linux.intel.com>]

Add kvm_cpu_cap_init_mf() to initialize CPUID leaves that encode
multi-bit value fields for specified overlays.

Unlike kvm_cpu_cap_init(), this helper directly assigns the provided
value without intersecting it with native CPUID or boot_cpu_data. This
is necessary because multi-bit fields encode numeric values, e.g.
address widths, field sizes, etc., where the value userspace wants to
expose to guests may differ from the native hardware value.

Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
---
 arch/x86/kvm/cpuid.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
index bdfaedb1cfcc..ea8ff5210e4a 100644
--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -259,6 +259,17 @@ static __always_inline void kvm_cpu_cap_check_and_set(unsigned int x86_feature,
 		kvm_cpu_cap_set(x86_feature, overlay_mask);
 }
 
+static __always_inline void kvm_cpu_cap_init_mf(u32 leaf, u32 features, u32 overlay_mask)
+{
+	WARN_ON_ONCE(!kvm_is_configuring_cpu_caps);
+	BUILD_BUG_ON(leaf >= NR_KVM_CPU_CAPS_PARANOID);
+
+	for (int i = 0; i < NR_CPUID_OL; i++) {
+		if (overlay_mask & BIT(i))
+			kvm_cpu_caps[i][leaf] = features;
+	}
+}
+
 static __always_inline bool guest_pv_has(struct kvm_vcpu *vcpu,
 					 unsigned int kvm_feature)
 {
-- 
2.46.0