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Subject[PATCH v4 03/17] x86/acrn: Introduce an API to check if a VM is privileged
Date
From: Yin Fengwei <fengwei.yin@intel.com>

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.

Signed-off-by: Yin Fengwei <fengwei.yin@intel.com>
Signed-off-by: Shuo Liu <shuo.a.liu@intel.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Fengwei Yin <fengwei.yin@intel.com>
Cc: Zhi Wang <zhi.a.wang@intel.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Yu Wang <yu1.wang@intel.com>
Cc: Reinette Chatre <reinette.chatre@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/include/asm/acrn.h | 9 +++++++++
arch/x86/kernel/cpu/acrn.c | 19 ++++++++++++++++++-
2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/acrn.h b/arch/x86/include/asm/acrn.h
index ff259b69cde7..a2d4aea3a80d 100644
--- a/arch/x86/include/asm/acrn.h
+++ b/arch/x86/include/asm/acrn.h
@@ -2,7 +2,16 @@
#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);
+bool acrn_is_privileged_vm(void);

#endif /* _ASM_X86_ACRN_H */
diff --git a/arch/x86/kernel/cpu/acrn.c b/arch/x86/kernel/cpu/acrn.c
index 42e88d01ccf9..b04fef8bd50b 100644
--- a/arch/x86/kernel/cpu/acrn.c
+++ b/arch/x86/kernel/cpu/acrn.c
@@ -21,9 +21,26 @@
#include <asm/idtentry.h>
#include <asm/irq_regs.h>

+static u32 acrn_cpuid_base(void)
+{
+ static u32 acrn_cpuid_base;
+
+ if (!acrn_cpuid_base && boot_cpu_has(X86_FEATURE_HYPERVISOR))
+ acrn_cpuid_base = hypervisor_cpuid_base("ACRNACRNACRN", 0);
+
+ return acrn_cpuid_base;
+}
+
+bool acrn_is_privileged_vm(void)
+{
+ return cpuid_eax(acrn_cpuid_base() | ACRN_CPUID_FEATURES) &
+ ACRN_FEATURE_PRIVILEGED_VM;
+}
+EXPORT_SYMBOL_GPL(acrn_is_privileged_vm);
+
static u32 __init acrn_detect(void)
{
- return hypervisor_cpuid_base("ACRNACRNACRN", 0);
+ return acrn_cpuid_base();
}

static void __init acrn_init_platform(void)
--
2.28.0
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