linux-kernel - [PATCH] KVM: x86: expose CPUID 0xC000_0000 for Zhaoxin "Shanghai" vendor

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Message-ID: <20250811013558.332940-1-ewanhai-oc@zhaoxin.com>
Date: Sun, 10 Aug 2025 21:35:58 -0400
From: Ewan Hai <ewanhai-oc@...oxin.com>
To: <seanjc@...gle.com>, <pbonzini@...hat.com>, <tglx@...utronix.de>,
	<mingo@...hat.com>, <bp@...en8.de>, <dave.hansen@...ux.intel.com>,
	<hpa@...or.com>
CC: <x86@...nel.org>, <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<ewanhai@...oxin.com>, <cobechen@...oxin.com>, <leoliu@...oxin.com>,
	<lyleli@...oxin.com>
Subject: [PATCH] KVM: x86: expose CPUID 0xC000_0000 for Zhaoxin "Shanghai" vendor

Both vendor IDs used by Zhaoxin ("  Shanghai  " and "Centaurhauls") rely
on leaf 0xC000_0000 to advertise the max 0xC000_00xx function. Extend
KVM so the leaf is returned for either ID and rename the local constant
CENTAUR_CPUID_SIGNATURE to ZHAOXIN_CPUID_SIGNATURE.  The constant is
used only inside cpuid.c, so the rename is NFC outside this file.

Signed-off-by: Ewan Hai <ewanhai-oc@...oxin.com>
---
 arch/x86/kvm/cpuid.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index e2836a255b16..beb83eaa1868 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -1811,7 +1811,7 @@ static int do_cpuid_func(struct kvm_cpuid_array *array, u32 func,
 	return __do_cpuid_func(array, func);
 }
 
-#define CENTAUR_CPUID_SIGNATURE 0xC0000000
+#define ZHAOXIN_CPUID_SIGNATURE 0xC0000000
 
 static int get_cpuid_func(struct kvm_cpuid_array *array, u32 func,
 			  unsigned int type)
@@ -1819,8 +1819,9 @@ static int get_cpuid_func(struct kvm_cpuid_array *array, u32 func,
 	u32 limit;
 	int r;
 
-	if (func == CENTAUR_CPUID_SIGNATURE &&
-	    boot_cpu_data.x86_vendor != X86_VENDOR_CENTAUR)
+	if (func == ZHAOXIN_CPUID_SIGNATURE &&
+		boot_cpu_data.x86_vendor != X86_VENDOR_CENTAUR &&
+		boot_cpu_data.x86_vendor != X86_VENDOR_ZHAOXIN)
 		return 0;
 
 	r = do_cpuid_func(array, func, type);
@@ -1869,7 +1870,7 @@ int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid,
 			    unsigned int type)
 {
 	static const u32 funcs[] = {
-		0, 0x80000000, CENTAUR_CPUID_SIGNATURE, KVM_CPUID_SIGNATURE,
+		0, 0x80000000, ZHAOXIN_CPUID_SIGNATURE, KVM_CPUID_SIGNATURE,
 	};
 
 	struct kvm_cpuid_array array = {
-- 
2.34.1