x86_64 and arm64 implementations to get the hypervisor version
information. Store these in hv_hypervisor_version_info structure to
simplify parsing the fields.

Replace the existing parsing when printing the version numbers at boot.

Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
---
 arch/arm64/hyperv/mshyperv.c      | 23 +++++++++++-------
 arch/x86/kernel/cpu/mshyperv.c    | 40 ++++++++++++++++++++-----------
 include/asm-generic/hyperv-tlfs.h | 23 ++++++++++++++++++
 include/asm-generic/mshyperv.h    |  2 ++
 4 files changed, 66 insertions(+), 22 deletions(-)

diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c
index f1b8a04ee9f2..53bdd3bc81ac 100644
--- a/arch/arm64/hyperv/mshyperv.c
+++ b/arch/arm64/hyperv/mshyperv.c
@@ -19,10 +19,19 @@
 
 static bool hyperv_initialized;
 
+int hv_get_hypervisor_version(union hv_hypervisor_version_info *info)
+{
+	hv_get_vpreg_128(HV_REGISTER_HYPERVISOR_VERSION,
+			 (struct hv_get_vp_registers_output *)info);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(hv_get_hypervisor_version);
+
 static int __init hyperv_init(void)
 {
-	struct hv_get_vp_registers_output	result;
-	u32	a, b, c, d;
+	struct hv_get_vp_registers_output result;
+	union hv_hypervisor_version_info version;
 	u64	guest_id;
 	int	ret;
 
@@ -55,13 +64,11 @@ static int __init hyperv_init(void)
 		ms_hyperv.misc_features);
 
 	/* Get information about the Hyper-V host version */
-	hv_get_vpreg_128(HV_REGISTER_HYPERVISOR_VERSION, &result);
-	a = result.as32.a;
-	b = result.as32.b;
-	c = result.as32.c;
-	d = result.as32.d;
+	hv_get_hypervisor_version(&version);
 	pr_info("Hyper-V: Host Build %d.%d.%d.%d-%d-%d\n",
-		b >> 16, b & 0xFFFF, a,	d & 0xFFFFFF, c, d >> 24);
+		version.major_version, version.minor_version,
+		version.build_number, version.service_number,
+		version.service_pack, version.service_branch);
 
 	ret = hv_common_init();
 	if (ret)
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 4d38cafe6f2c..e80e503c8cf5 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -313,13 +313,30 @@ static void __init hv_smp_prepare_cpus(unsigned int max_cpus)
 }
 #endif
 
+int hv_get_hypervisor_version(union hv_hypervisor_version_info *info)
+{
+	unsigned int hv_max_functions;
+
+	hv_max_functions = cpuid_eax(HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS);
+	if (hv_max_functions < HYPERV_CPUID_VERSION) {
+		pr_err("%s: Could not detect Hyper-V version\n",
+			__func__);
+		return -ENODEV;
+	}
+
+	info->eax = cpuid_eax(HYPERV_CPUID_VERSION);
+	info->ebx = cpuid_ebx(HYPERV_CPUID_VERSION);
+	info->ecx = cpuid_ecx(HYPERV_CPUID_VERSION);
+	info->edx = cpuid_edx(HYPERV_CPUID_VERSION);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(hv_get_hypervisor_version);
+
 static void __init ms_hyperv_init_platform(void)
 {
 	int hv_max_functions_eax;
-	int hv_host_info_eax;
-	int hv_host_info_ebx;
-	int hv_host_info_ecx;
-	int hv_host_info_edx;
+	union hv_hypervisor_version_info version;
 
 #ifdef CONFIG_PARAVIRT
 	pv_info.name = "Hyper-V";
@@ -373,16 +390,11 @@ static void __init ms_hyperv_init_platform(void)
 	/*
 	 * Extract host information.
 	 */
-	if (hv_max_functions_eax >= HYPERV_CPUID_VERSION) {
-		hv_host_info_eax = cpuid_eax(HYPERV_CPUID_VERSION);
-		hv_host_info_ebx = cpuid_ebx(HYPERV_CPUID_VERSION);
-		hv_host_info_ecx = cpuid_ecx(HYPERV_CPUID_VERSION);
-		hv_host_info_edx = cpuid_edx(HYPERV_CPUID_VERSION);
-
-		pr_info("Hyper-V: Host Build %d.%d.%d.%d-%d-%d\n",
-			hv_host_info_ebx >> 16, hv_host_info_ebx & 0xFFFF,
-			hv_host_info_eax, hv_host_info_edx & 0xFFFFFF,
-			hv_host_info_ecx, hv_host_info_edx >> 24);
+	if (hv_get_hypervisor_version(&version) == 0) {
+		pr_info("Hyper-V Host Build:%d-%d.%d-%d-%d.%d\n",
+			version.build_number, version.major_version,
+			version.minor_version, version.service_pack,
+			version.service_branch, version.service_number);
 	}
 
 	if (ms_hyperv.features & HV_ACCESS_FREQUENCY_MSRS &&
diff --git a/include/asm-generic/hyperv-tlfs.h b/include/asm-generic/hyperv-tlfs.h
index f4e4cc4f965f..373f26efa18a 100644
--- a/include/asm-generic/hyperv-tlfs.h
+++ b/include/asm-generic/hyperv-tlfs.h
@@ -786,6 +786,29 @@ struct hv_input_unmap_device_interrupt {
 #define HV_SOURCE_SHADOW_NONE               0x0
 #define HV_SOURCE_SHADOW_BRIDGE_BUS_RANGE   0x1
 
+/*
+ * Version info reported by hypervisor
+ */
+union hv_hypervisor_version_info {
+	struct {
+		u32 build_number;
+
+		u32 minor_version : 16;
+		u32 major_version : 16;
+
+		u32 service_pack;
+
+		u32 service_number : 24;
+		u32 service_branch : 8;
+	};
+	struct {
+		u32 eax;
+		u32 ebx;
+		u32 ecx;
+		u32 edx;
+	};
+};
+
 /*
  * The whole argument should fit in a page to be able to pass to the hypervisor
  * in one hypercall.
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index 094c57320ed1..233c976344e5 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -153,6 +153,8 @@ static inline void vmbus_signal_eom(struct hv_message *msg, u32 old_msg_type)
 	}
 }
 
+int hv_get_hypervisor_version(union hv_hypervisor_version_info *info);
+
 void hv_setup_vmbus_handler(void (*handler)(void));
 void hv_remove_vmbus_handler(void);
 void hv_setup_stimer0_handler(void (*handler)(void));
-- 
2.25.1

On 8/17/23 15:01, Nuno Das Neves wrote:
> +int hv_get_hypervisor_version(union hv_hypervisor_version_info *info)
> +{
> +	hv_get_vpreg_128(HV_REGISTER_HYPERVISOR_VERSION,
> +			 (struct hv_get_vp_registers_output *)info);
> +
> +	return 0;
> +}
...
> +int hv_get_hypervisor_version(union hv_hypervisor_version_info *info)
> +{
> +	unsigned int hv_max_functions;
> +
> +	hv_max_functions = cpuid_eax(HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS);
> +	if (hv_max_functions < HYPERV_CPUID_VERSION) {
> +		pr_err("%s: Could not detect Hyper-V version\n",
> +			__func__);
> +		return -ENODEV;
> +	}
> +
> +	info->eax = cpuid_eax(HYPERV_CPUID_VERSION);
> +	info->ebx = cpuid_ebx(HYPERV_CPUID_VERSION);
> +	info->ecx = cpuid_ecx(HYPERV_CPUID_VERSION);
> +	info->edx = cpuid_edx(HYPERV_CPUID_VERSION);
> +
> +	return 0;
> +}

I can't help but notice that the ARM version does *one* call to the
hardware while the x86 version does CPUID four different times, once to
get *EACH* register and throwing away the other three registers each
time.  Also recall that CPUID is a big, fat architecturally serializing
instruction.  This isn't a fast path, but CPUID is about as slow as you get.

Is there any reason you can't just have an x86 version of
hv_get_vpreg_128() that gets the 128 bits bytes of data that comes back
in the 4 CPUID registers?

That might even let you share some more code.

On 8/17/2023 4:14 PM, Dave Hansen wrote:
> On 8/17/23 15:01, Nuno Das Neves wrote:
>> +int hv_get_hypervisor_version(union hv_hypervisor_version_info *info)
>> +{
>> +	hv_get_vpreg_128(HV_REGISTER_HYPERVISOR_VERSION,
>> +			 (struct hv_get_vp_registers_output *)info);
>> +
>> +	return 0;
>> +}
> ...
>> +int hv_get_hypervisor_version(union hv_hypervisor_version_info *info)
>> +{
>> +	unsigned int hv_max_functions;
>> +
>> +	hv_max_functions = cpuid_eax(HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS);
>> +	if (hv_max_functions < HYPERV_CPUID_VERSION) {
>> +		pr_err("%s: Could not detect Hyper-V version\n",
>> +			__func__);
>> +		return -ENODEV;
>> +	}
>> +
>> +	info->eax = cpuid_eax(HYPERV_CPUID_VERSION);
>> +	info->ebx = cpuid_ebx(HYPERV_CPUID_VERSION);
>> +	info->ecx = cpuid_ecx(HYPERV_CPUID_VERSION);
>> +	info->edx = cpuid_edx(HYPERV_CPUID_VERSION);
>> +
>> +	return 0;
>> +}
> 
> I can't help but notice that the ARM version does *one* call to the
> hardware while the x86 version does CPUID four different times, once to
> get *EACH* register and throwing away the other three registers each
> time.  Also recall that CPUID is a big, fat architecturally serializing
> instruction.  This isn't a fast path, but CPUID is about as slow as you get.
> 

Good point, it is quite wasteful. I just went and checked cpuid.h, and of
course there is a generic cpuid() function that can get all 4 at once.
I will update it to use this in the next version. Thanks!

> Is there any reason you can't just have an x86 version of
> hv_get_vpreg_128() that gets the 128 bits bytes of data that comes back
> in the 4 CPUID registers?
> 
> That might even let you share some more code.

Unfortunately, for some reason the hypervisor only lets you get this data via
CPUID on x86_64, and via hypercall - i.e. hv_get_vpreg_128() - on ARM64.