From: Sean Christopherson <sean.j.christopherson@intel.com>
Date: Mon, 2 Mar 2020 23:56:49 +0000 (-0800)
Subject: KVM: x86: Remove the unnecessary loop on CPUID 0x7 sub-leafs
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=bcf600ca8d21e49af21fec5d2cf3927d6f62d048;p=linux.git

KVM: x86: Remove the unnecessary loop on CPUID 0x7 sub-leafs

Explicitly handle CPUID 0x7 sub-leaf 1.  The kernel is currently aware
of exactly one feature in CPUID 0x7.1,  which means there is room for
another 127 features before CPUID 0x7.2 will see the light of day, i.e.
the looping is likely to be dead code for years to come.

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index f6d3121656cc2..cce78723376cf 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -536,11 +536,9 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 		if (boot_cpu_has(X86_FEATURE_AMD_SSBD))
 			cpuid_entry_set(entry, X86_FEATURE_SPEC_CTRL_SSBD);
 
-		for (i = 1, max_idx = entry->eax; i <= max_idx; i++) {
-			if (WARN_ON_ONCE(i > 1))
-				break;
-
-			entry = do_host_cpuid(array, function, i);
+		/* KVM only supports 0x7.0 and 0x7.1, capped above via min(). */
+		if (entry->eax == 1) {
+			entry = do_host_cpuid(array, function, 1);
 			if (!entry)
 				goto out;