[PATCHv2] x86info: dump kvm cpuid's

Michael S. Tsirkin
Mon, 30 Apr 2012 14:38:35 -0000

The following makes 'x86info -r' dump hypervisor leaf cpu ids
(for kvm this is signature+features) when running in a vm.

On the guest we see the signature and the features:
eax in: 0x40000000, eax = 00000000 ebx = 4b4d564b ecx = 564b4d56 edx = 0000004d
eax in: 0x40000001, eax = 0100007b ebx = 00000000 ecx = 00000000 edx = 00000000

Hypervisor flag is checked to avoid output changes when not
running on a VM.

Signed-off-by: Michael S. Tsirkin <mst at redhat.com>

Changes from v1:
	Make work on non KVM hypervisors (only KVM was tested).
	Avi Kivity said kvm will in the future report
	max HV leaf in eax. For now it reports eax = 0
        so add a work around for that.

---

diff --git a/identify.c b/identify.c
index 33f35de..a4a3763 100644
--- a/identify.c
+++ b/identify.c
@@ -9,8 +9,8 @@

 void get_cpu_info_basics(struct cpudata *cpu)
 {
-	unsigned int maxi, maxei, vendor, address_bits;
-	unsigned int eax;
+	unsigned int maxi, maxei, maxhv, vendor, address_bits;
+	unsigned int eax, ebx, ecx;

 	cpuid(cpu->number, 0, &maxi, &vendor, NULL, NULL);
 	maxi &= 0xffff;		/* The high-order word is non-zero on some Cyrix CPUs */
@@ -19,7 +19,7 @@ void get_cpu_info_basics(struct cpudata *cpu)
 		return;

 	/* Everything that supports cpuid supports these. */
-	cpuid(cpu->number, 1, &eax, NULL, NULL, NULL);
+	cpuid(cpu->number, 1, &eax, &ebx, &ecx, NULL);
 	cpu->stepping = eax & 0xf;
 	cpu->model = (eax >> 4) & 0xf;
 	cpu->family = (eax >> 8) & 0xf;
@@ -29,6 +29,19 @@ void get_cpu_info_basics(struct cpudata *cpu)

 	cpuid(cpu->number, 0xC0000000, &maxei, NULL, NULL, NULL);
 	cpu->maxei2 = maxei;
+	if (ecx & 0x80000000) {
+		cpuid(cpu->number, 0x40000000, &maxhv, NULL, NULL, NULL);
+		/*
+		 * KVM up to linux 3.4 reports 0 as the max hypervisor leaf,
+		 * where it really means 0x40000001.
+		 * Most (all?) hypervisors have at least one CPUID besides
+		 * the vendor ID so assume that.
+		 */
+		cpu->maxhv = maxhv ? maxhv : 0x40000001;
+	} else {
+		/* Suppress hypervisor cpuid unless running on a hypervisor */
+		cpu->maxhv = 0;
+	}

 	cpuid(cpu->number, 0x80000008,&address_bits, NULL, NULL, NULL);
 	cpu->phyaddr_bits = address_bits & 0xFF;
diff --git a/x86info.c b/x86info.c
index 22c4734..80cae36 100644
--- a/x86info.c
+++ b/x86info.c
@@ -44,6 +44,10 @@ static void display_detailed_info(struct cpudata *cpu)

 		if (cpu->maxei2 >=0xC0000000)
 			dump_raw_cpuid(cpu->number, 0xC0000000, cpu->maxei2);
+
+		if (cpu->maxhv >= 0x40000000)
+			dump_raw_cpuid(cpu->number, 0x40000000, cpu->maxhv);
+
 	}

 	if (show_cacheinfo) {
diff --git a/x86info.h b/x86info.h
index 7d2a455..c4f5d81 100644
--- a/x86info.h
+++ b/x86info.h
@@ -84,7 +84,7 @@ struct cpudata {
 	unsigned int cachesize_trace;
 	unsigned int phyaddr_bits;
 	unsigned int viraddr_bits;
-	unsigned int cpuid_level, maxei, maxei2;
+	unsigned int cpuid_level, maxei, maxei2, maxhv;
 	char name[CPU_NAME_LEN];
 	enum connector connector;
 	unsigned int flags_ecx;