[PATCH 1/4] x86: introduce hypervisor_cpuid_base()

From: Jason Wang <jasowang@redhat.com>
To: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
	x86@kernel.org, gleb@redhat.com, pbonzini@redhat.com,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Jason Wang <jasowang@redhat.com>
Subject: [PATCH 1/4] x86: introduce hypervisor_cpuid_base()
Date: Tue, 23 Jul 2013 17:41:02 +0800	[thread overview]
Message-ID: <1374572465-15278-1-git-send-email-jasowang@redhat.com> (raw)

This patch introduce hypervisor_cpuid_base() which loop test the hypervisor
existence function until the signature match and check the number of leaves if
required. This could be used by Xen/KVM guest to detect the existence of
hypervisor.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Paolo Bonzini" <pbonzini@redhat.com>
Cc: Gleb Natapov <gleb@redhat.com>
Cc: x86@kernel.org
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 arch/x86/include/asm/processor.h |   20 ++++++++++++++++++++
 1 files changed, 20 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 24cf5ae..a8136d0 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -971,6 +971,26 @@ unsigned long calc_aperfmperf_ratio(struct aperfmperf *old,
 	return ratio;
 }
 
+static inline uint32_t hypervisor_cpuid_base(const char *sig, uint32_t leaves)
+{
+	uint32_t base, eax, ebx, ecx, edx;
+	char signature[13];
+
+	for (base = 0x40000000; base < 0x40010000; base += 0x100) {
+		cpuid(base, &eax, &ebx, &ecx, &edx);
+		*(uint32_t *)(signature + 0) = ebx;
+		*(uint32_t *)(signature + 4) = ecx;
+		*(uint32_t *)(signature + 8) = edx;
+		signature[12] = 0;
+
+		if (!strcmp(sig, signature) &&
+		    (leaves == 0 || ((eax - base) >= leaves)))
+			return base;
+	}
+
+	return 0;
+}
+
 extern unsigned long arch_align_stack(unsigned long sp);
 extern void free_init_pages(char *what, unsigned long begin, unsigned long end);
 
-- 
1.7.1

