RE: [PATCH] mshyperv: Introduce hv_get_hypervisor_version function

[Michael Kelley]

From: Nuno Das Neves <nunodasneves@xxxxxxxxxxxxxxxxxxx> Sent: Wednesday, March 6, 2024 4:48 PM
> 
> Introduce x86_64 and arm64 functions for getting the hypervisor version
> information and storing it in a structure for simpler parsing.
> 
> Use the new function to get and parse the version at boot time. While at
> it, print the version in the same format for each architecture, and move
> the printing code to hv_common_init() so it is not duplicated.

Isn't the format already the same for x86 and ARM64?   A couple of
years ago they didn't match.  But that was fixed in commit eeda29db98f4.

> 
> Signed-off-by: Nuno Das Neves <nunodasneves@xxxxxxxxxxxxxxxxxxx>
> Acked-by: Wei Liu <wei.liu@xxxxxxxxxx>
> ---
>  arch/arm64/hyperv/mshyperv.c      | 19 ++++++++---------
>  arch/x86/kernel/cpu/mshyperv.c    | 35 ++++++++++++++-----------------
>  drivers/hv/hv_common.c            |  9 ++++++++
>  include/asm-generic/hyperv-tlfs.h | 23 ++++++++++++++++++++
>  include/asm-generic/mshyperv.h    |  2 ++
>  5 files changed, 59 insertions(+), 29 deletions(-)
> 
> diff --git a/arch/arm64/hyperv/mshyperv.c
> b/arch/arm64/hyperv/mshyperv.c
> index f1b8a04ee9f2..55dc224d466d 100644
> --- a/arch/arm64/hyperv/mshyperv.c
> +++ b/arch/arm64/hyperv/mshyperv.c
> @@ -19,10 +19,18 @@
> 
>  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);

I don't think this need to be exported, at least not for the usage in
this patch.  The caller in hv_common.c is never part of a module -- it's
always built-in. But maybe you are anticipating future use cases
from a module?

> +
>  static int __init hyperv_init(void)
>  {
>  	struct hv_get_vp_registers_output	result;
> -	u32	a, b, c, d;
>  	u64	guest_id;
>  	int	ret;
> 
> @@ -54,15 +62,6 @@ static int __init hyperv_init(void)
>  		ms_hyperv.features, ms_hyperv.priv_high, ms_hyperv.hints,
>  		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;
> -	pr_info("Hyper-V: Host Build %d.%d.%d.%d-%d-%d\n",
> -		b >> 16, b & 0xFFFF, a,	d & 0xFFFFFF, c, d >> 24);
> -
>  	ret = hv_common_init();
>  	if (ret)
>  		return ret;
> diff --git a/arch/x86/kernel/cpu/mshyperv.c
> b/arch/x86/kernel/cpu/mshyperv.c
> index d306f6184cee..03a3445faf7a 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -350,13 +350,25 @@ static void __init reduced_hw_init(void)
>  	x86_init.irqs.pre_vector_init	= x86_init_noop;
>  }
> 
> +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;
> +	}
> +
> +	cpuid(HYPERV_CPUID_VERSION, &info->eax, &info->ebx, &info->ecx, &info->edx);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(hv_get_hypervisor_version);

Same for this EXPORT.

> +
>  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;
> 
>  #ifdef CONFIG_PARAVIRT
>  	pv_info.name = "Hyper-V";
> @@ -407,21 +419,6 @@ static void __init ms_hyperv_init_platform(void)
>  		pr_info("Hyper-V: running on a nested hypervisor\n");
>  	}
> 
> -	/*
> -	 * 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 (ms_hyperv.features & HV_ACCESS_FREQUENCY_MSRS &&
>  	    ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE) {
>  		x86_platform.calibrate_tsc = hv_get_tsc_khz;
> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> index 2f1dd4b07f9a..4d72c528af68 100644
> --- a/drivers/hv/hv_common.c
> +++ b/drivers/hv/hv_common.c
> @@ -278,6 +278,15 @@ static void hv_kmsg_dump_register(void)
>  int __init hv_common_init(void)
>  {
>  	int i;
> +	union hv_hypervisor_version_info version;
> +
> +	/* Get information about the Hyper-V host version */
> +	if (hv_get_hypervisor_version(&version) == 0) {

The usual idiom would be:

	if (!hv_get_hypervisor_version(&version)) {

> +		pr_info("Hyper-V: Host Build %d.%d.%d.%d-%d-%d\n",
> +			version.major_version, version.minor_version,
> +			version.build_number, version.service_number,
> +			version.service_pack, version.service_branch);
> +	}
> 
>  	if (hv_is_isolation_supported())
>  		sysctl_record_panic_msg = 0;
> diff --git a/include/asm-generic/hyperv-tlfs.h b/include/asm-generic/hyperv-tlfs.h
> index 3d1b31f90ed6..32514a870b98 100644
> --- a/include/asm-generic/hyperv-tlfs.h
> +++ b/include/asm-generic/hyperv-tlfs.h
> @@ -817,6 +817,29 @@ 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;

Nit:  These names are x86-isms appearing in the generic portion
of hyperv-tlfs.h.  On the ARM64 side I had called the four parts
"a", "b", "c", and "d" to be slightly more generic.  But if want to
keep the x86 register names, I won't object.

Michael

> +	};
> +};
> +
>  /*
>   * 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 04424a446bb7..452b7c089b71 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -161,6 +161,8 @@ 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
>