x86/acrn: Introduce acrn_cpuid_base() and hypervisor feature bits

ACRN Hypervisor reports hypervisor features via CPUID leaf 0x40000001
which is similar to KVM. A VM can check if it's the privileged VM using
the feature bits. The Service VM is the only privileged VM by design.

Cc: Dave Hansen <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Fengwei Yin <[email protected]>
Cc: Zhi Wang <[email protected]>
Cc: Zhenyu Wang <[email protected]>
Cc: Yu Wang <[email protected]>
Cc: Reinette Chatre <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Reviewed-by: Reinette Chatre <[email protected]>
Acked-by: Borislav Petkov <[email protected]>
Signed-off-by: Yin Fengwei <[email protected]>
Signed-off-by: Shuo Liu <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

2 files changed, 17 insertions, 1 deletions

diff --git a/arch/x86/include/asm/acrn.h b/arch/x86/include/asm/acrn.h
index ff259b69cde7..127f20672c5d 100644
--- a/arch/x86/include/asm/acrn.h
+++ b/arch/x86/include/asm/acrn.h
@@ -2,7 +2,23 @@
 #ifndef _ASM_X86_ACRN_H
 #define _ASM_X86_ACRN_H
 
+/*
+ * This CPUID returns feature bitmaps in EAX.
+ * Guest VM uses this to detect the appropriate feature bit.
+ */
+#define	ACRN_CPUID_FEATURES		0x40000001
+/* Bit 0 indicates whether guest VM is privileged */
+#define	ACRN_FEATURE_PRIVILEGED_VM	BIT(0)
+
 void acrn_setup_intr_handler(void (*handler)(void));
 void acrn_remove_intr_handler(void);
 
+static inline u32 acrn_cpuid_base(void)
+{
+	if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
+		return hypervisor_cpuid_base("ACRNACRNACRN", 0);
+
+	return 0;
+}
+
 #endif /* _ASM_X86_ACRN_H */
diff --git a/arch/x86/kernel/cpu/acrn.c b/arch/x86/kernel/cpu/acrn.c
index e0c181781905..23f5f27b5a02 100644
--- a/arch/x86/kernel/cpu/acrn.c
+++ b/arch/x86/kernel/cpu/acrn.c
@@ -21,7 +21,7 @@
 
 static u32 __init acrn_detect(void)
 {
-	return hypervisor_cpuid_base("ACRNACRNACRN", 0);
+	return acrn_cpuid_base();
 }
 
 static void __init acrn_init_platform(void)