KVM: x86/pvm: Remove KVM_CPUID_VENDOR_FEATURES

PVM is the only variant that places the guest kernel in a state where
the underlying IF == 1 and underlying CS == 3, no vendor leaf needed.

Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>

Author: Lai Jiangshan

arch/x86/include/uapi/asm/kvm_para.h

@@ -5,9 +5,7 @@
 #include <linux/types.h>
 
 /* This CPUID returns the signature 'KVMKVMKVM' in ebx, ecx, and edx.  It
- * should be used to determine that a VM is running under KVM. And it
- * returns KVM_CPUID_FEATURES in eax if vendor feature is not enabled,
- * otherwise KVM_CPUID_VENDOR_FEATURES.
+ * should be used to determine that a VM is running under KVM.
  */
 #define KVM_CPUID_SIGNATURE	0x40000000
 #define KVM_SIGNATURE "KVMKVMKVM\0\0\0"
@@ -18,10 +16,6 @@
  * in edx.
  */
 #define KVM_CPUID_FEATURES	0x40000001
-/* This CPUID returns the vendor feature bitmaps in eax and the vendor
- * signature in ebx.
- */
-#define KVM_CPUID_VENDOR_FEATURES	0x40000002
 #define KVM_FEATURE_CLOCKSOURCE		0
 #define KVM_FEATURE_NOP_IO_DELAY	1
 #define KVM_FEATURE_MMU_OP		2

arch/x86/include/uapi/asm/pvm_para.h

@@ -5,12 +5,12 @@
 #include <linux/const.h>
 
 /*
- * The CPUID instruction in PVM guest can't be trapped and emulated,
+ * The CPUID instruction in PVM guest might not be trapped and emulated,
  * so PVM guest should use the following two instructions instead:
  * "invlpg 0xffffffffff4d5650; cpuid;"
  *
- * PVM_SYNTHETIC_CPUID is supposed to not trigger any trap in the real or
- * virtual x86 kernel mode and is also guaranteed to trigger a trap in the
+ * PVM_SYNTHETIC_CPUID is supposed to not trigger any trap in the real or any
+ * paravirtual x86 kernel mode and is also guaranteed to trigger a trap in the
  * underlying hardware user mode for the hypervisor emulating it. The
  * hypervisor emulates both of the basic instructions, while the INVLPG is
  * often emulated as an NOP since 0xffffffffff4d5650 is normally out of the
@@ -20,12 +20,6 @@
 					0x56,0x4d,0xff,0x0f,0xa2
 #define PVM_SYNTHETIC_CPUID_ADDRESS	0xffffffffff4d5650
 
-/*
- * The vendor signature 'PVM' is returned in ebx. It should be used to
- * determine that a VM is running under PVM.
- */
-#define PVM_CPUID_SIGNATURE		0x4d5650
-
 /*
  * PVM virtual MSRS falls in the range 0x4b564df0-0x4b564dff, and it should not
  * conflict with KVM, see arch/x86/include/uapi/asm/kvm_para.h

arch/x86/kvm/cpuid.c

@@ -36,16 +36,6 @@
 u32 kvm_cpu_caps[NR_KVM_CPU_CAPS] __read_mostly;
 EXPORT_SYMBOL_GPL(kvm_cpu_caps);
 
-u32 kvm_cpuid_vendor_features;
-EXPORT_SYMBOL_GPL(kvm_cpuid_vendor_features);
-u32 kvm_cpuid_vendor_signature;
-EXPORT_SYMBOL_GPL(kvm_cpuid_vendor_signature);
-
-static inline bool has_kvm_cpuid_vendor_features(void)
-{
-	return !!kvm_cpuid_vendor_signature;
-}
-
 u32 xstate_required_size(u64 xstate_bv, bool compacted)
 {
 	int feature_bit = 0;
@@ -1142,10 +1132,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 		break;
 	case KVM_CPUID_SIGNATURE: {
 		const u32 *sigptr = (const u32 *)KVM_SIGNATURE;
-		if (!has_kvm_cpuid_vendor_features())
-			entry->eax = KVM_CPUID_FEATURES;
-		else
-			entry->eax = KVM_CPUID_VENDOR_FEATURES;
+		entry->eax = KVM_CPUID_FEATURES;
 		entry->ebx = sigptr[0];
 		entry->ecx = sigptr[1];
 		entry->edx = sigptr[2];
@@ -1173,17 +1160,6 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 		entry->ecx = 0;
 		entry->edx = 0;
 		break;
-	case KVM_CPUID_VENDOR_FEATURES:
-		if (!has_kvm_cpuid_vendor_features()) {
-			entry->eax = 0;
-			entry->ebx = 0;
-		} else {
-			entry->eax = kvm_cpuid_vendor_features;
-			entry->ebx = kvm_cpuid_vendor_signature;
-		}
-		entry->ecx = 0;
-		entry->edx = 0;
-		break;
 	case 0x80000000:
 		entry->eax = min(entry->eax, 0x80000022);
 		/*

arch/x86/kvm/cpuid.h

@@ -8,9 +8,6 @@
 #include <asm/processor.h>
 #include <uapi/asm/kvm_para.h>
 
-extern u32 kvm_cpuid_vendor_features;
-extern u32 kvm_cpuid_vendor_signature;
-
 extern u32 kvm_cpu_caps[NR_KVM_CPU_CAPS] __read_mostly;
 void kvm_set_cpu_caps(void);
 

arch/x86/kvm/pvm/pvm.c

@@ -3265,7 +3265,6 @@ static void pvm_exit(void)
 	kvm_x86_vendor_exit();
 	host_mmu_destroy();
 	allow_smaller_maxphyaddr = false;
-	kvm_cpuid_vendor_signature = 0;
 }
 module_exit(pvm_exit);
 
@@ -3330,7 +3329,6 @@ static int __init pvm_init(void)
 		goto exit_vendor;
 
 	allow_smaller_maxphyaddr = true;
-	kvm_cpuid_vendor_signature = PVM_CPUID_SIGNATURE;
 
 	return 0;