RE: [PATCH v3 1/2] hyperv: Move hv_current_partition_id to arch-generic code

[Michael Kelley <mhklinux@outlook.com>]

From: Nuno Das Neves <nunodasneves@linux.microsoft.com> Sent: Friday, February 7, 2025 11:03 AM
> 
> Move hv_current_partition_id and hv_get_partition_id() to hv_common.c,
> and call hv_get_partition_id() on arm64 in hyperv_init(). These aren't
> specific to x86_64 and will be needed by common code.
> 
> Set hv_current_partition_id to HV_PARTITION_ID_SELF by default.
> 
> Rename struct hv_get_partition_id to hv_output_get_partition_id, to
> make it distinct from the function hv_get_partition_id(), and match
> the original Hyper-V struct name.
> 
> Remove the BUG()s. Failing to get the id need not crash the machine.
> 
> Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>

Looks good now.

Reviewed-by: Michael Kelley <mhklinux@outlook.com>

> ---
>  arch/arm64/hyperv/mshyperv.c    |  3 +++
>  arch/x86/hyperv/hv_init.c       | 25 +------------------------
>  arch/x86/include/asm/mshyperv.h |  2 --
>  drivers/hv/hv_common.c          | 22 ++++++++++++++++++++++
>  include/asm-generic/mshyperv.h  |  2 ++
>  include/hyperv/hvgdk_mini.h     |  2 +-
>  6 files changed, 29 insertions(+), 27 deletions(-)
> 
> diff --git a/arch/arm64/hyperv/mshyperv.c b/arch/arm64/hyperv/mshyperv.c
> index fc49949b7df6..29fcfd595f48 100644
> --- a/arch/arm64/hyperv/mshyperv.c
> +++ b/arch/arm64/hyperv/mshyperv.c
> @@ -72,6 +72,9 @@ static int __init hyperv_init(void)
>  		return ret;
>  	}
> 
> +	if (ms_hyperv.priv_high & HV_ACCESS_PARTITION_ID)
> +		hv_get_partition_id();
> +
>  	ms_hyperv_late_init();
> 
>  	hyperv_initialized = true;
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 173005e6a95d..9be1446f5bd3 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -34,9 +34,6 @@
>  #include <clocksource/hyperv_timer.h>
>  #include <linux/highmem.h>
> 
> -u64 hv_current_partition_id = ~0ull;
> -EXPORT_SYMBOL_GPL(hv_current_partition_id);
> -
>  void *hv_hypercall_pg;
>  EXPORT_SYMBOL_GPL(hv_hypercall_pg);
> 
> @@ -393,24 +390,6 @@ static void __init hv_stimer_setup_percpu_clockev(void)
>  		old_setup_percpu_clockev();
>  }
> 
> -static void __init hv_get_partition_id(void)
> -{
> -	struct hv_get_partition_id *output_page;
> -	u64 status;
> -	unsigned long flags;
> -
> -	local_irq_save(flags);
> -	output_page = *this_cpu_ptr(hyperv_pcpu_output_arg);
> -	status = hv_do_hypercall(HVCALL_GET_PARTITION_ID, NULL, output_page);
> -	if (!hv_result_success(status)) {
> -		/* No point in proceeding if this failed */
> -		pr_err("Failed to get partition ID: %lld\n", status);
> -		BUG();
> -	}
> -	hv_current_partition_id = output_page->partition_id;
> -	local_irq_restore(flags);
> -}
> -
>  #if IS_ENABLED(CONFIG_HYPERV_VTL_MODE)
>  static u8 __init get_vtl(void)
>  {
> @@ -605,11 +584,9 @@ void __init hyperv_init(void)
> 
>  	register_syscore_ops(&hv_syscore_ops);
> 
> -	if (cpuid_ebx(HYPERV_CPUID_FEATURES) & HV_ACCESS_PARTITION_ID)
> +	if (ms_hyperv.priv_high & HV_ACCESS_PARTITION_ID)
>  		hv_get_partition_id();
> 
> -	BUG_ON(hv_root_partition && hv_current_partition_id == ~0ull);
> -
>  #ifdef CONFIG_PCI_MSI
>  	/*
>  	 * If we're running as root, we want to create our own PCI MSI domain.
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index f91ab1e75f9f..8d3ada3e8d0d 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -43,8 +43,6 @@ extern bool hyperv_paravisor_present;
> 
>  extern void *hv_hypercall_pg;
> 
> -extern u64 hv_current_partition_id;
> -
>  extern union hv_ghcb * __percpu *hv_ghcb_pg;
> 
>  bool hv_isolation_type_snp(void);
> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> index af5d1dc451f6..cb3ea49020ef 100644
> --- a/drivers/hv/hv_common.c
> +++ b/drivers/hv/hv_common.c
> @@ -31,6 +31,9 @@
>  #include <hyperv/hvhdk.h>
>  #include <asm/mshyperv.h>
> 
> +u64 hv_current_partition_id = HV_PARTITION_ID_SELF;
> +EXPORT_SYMBOL_GPL(hv_current_partition_id);
> +
>  /*
>   * hv_root_partition, ms_hyperv and hv_nested are defined here with other
>   * Hyper-V specific globals so they are shared across all architectures and are
> @@ -283,6 +286,25 @@ static inline bool hv_output_page_exists(void)
>  	return hv_root_partition || IS_ENABLED(CONFIG_HYPERV_VTL_MODE);
>  }
> 
> +void __init hv_get_partition_id(void)
> +{
> +	struct hv_output_get_partition_id *output;
> +	unsigned long flags;
> +	u64 status, pt_id;
> +
> +	local_irq_save(flags);
> +	output = *this_cpu_ptr(hyperv_pcpu_input_arg);
> +	status = hv_do_hypercall(HVCALL_GET_PARTITION_ID, NULL, &output);
> +	pt_id = output->partition_id;
> +	local_irq_restore(flags);
> +
> +	if (hv_result_success(status))
> +		hv_current_partition_id = pt_id;
> +	else
> +		pr_err("Hyper-V: failed to get partition ID: %#lx\n",
> +		       hv_result(status));
> +}
> +
>  int __init hv_common_init(void)
>  {
>  	int i;
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> index a7bbe504e4f3..febeddf6cd8a 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -58,6 +58,7 @@ struct ms_hyperv_info {
>  };
>  extern struct ms_hyperv_info ms_hyperv;
>  extern bool hv_nested;
> +extern u64 hv_current_partition_id;
> 
>  extern void * __percpu *hyperv_pcpu_input_arg;
>  extern void * __percpu *hyperv_pcpu_output_arg;
> @@ -207,6 +208,7 @@ extern u64 (*hv_read_reference_counter)(void);
>  #define VP_INVAL	U32_MAX
> 
>  int __init hv_common_init(void);
> +void __init hv_get_partition_id(void);
>  void __init hv_common_free(void);
>  void __init ms_hyperv_late_init(void);
>  int hv_common_cpu_init(unsigned int cpu);
> diff --git a/include/hyperv/hvgdk_mini.h b/include/hyperv/hvgdk_mini.h
> index 155615175965..58895883f636 100644
> --- a/include/hyperv/hvgdk_mini.h
> +++ b/include/hyperv/hvgdk_mini.h
> @@ -182,7 +182,7 @@ struct hv_tsc_emulation_control {	 /*
> HV_TSC_INVARIANT_CONTROL */
> 
>  #endif /* CONFIG_X86 */
> 
> -struct hv_get_partition_id {	 /* HV_OUTPUT_GET_PARTITION_ID */
> +struct hv_output_get_partition_id {
>  	u64 partition_id;
>  } __packed;
> 
> --
> 2.34.1