Re: [PATCH 1/2] hyperv: Fix pointer type for the output of the hypercall in get_vtl(void)

[Nuno Das Neves <nunodasneves@linux.microsoft.com>]

On 12/18/2024 12:54 PM, Roman Kisel wrote:
> Commit bc905fa8b633 ("hyperv: Switch from hyperv-tlfs.h to hyperv/hvhdk.h")
> changed the type of the output pointer to `struct hv_register_assoc` from
> `struct hv_get_vp_registers_output`. That leads to an incorrect computation,
> and leaves the system broken.
> 
My bad! But, lets not use `struct hv_get_registers_output`. Instead, use
`struct hv_register_value`, since that is the more complete definition of a
register value. The output of the get_vp_registers hypercall is just an array
of these values.

Ideally we remove `struct hv_get_vp_registers_output` at some point, since
it serves the same role as `struct hv_register_value` but in a more limited
capacity.

Thanks
Nuno

> Use the correct pointer type for the output of the GetVpRegisters hypercall.
> 
> Fixes: bc905fa8b633 ("hyperv: Switch from hyperv-tlfs.h to hyperv/hvhdk.h")
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
> ---
>  arch/x86/hyperv/hv_init.c   | 6 +++---
>  include/hyperv/hvgdk_mini.h | 3 ---
>  2 files changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 3cf2a227d666..c7185c6a290b 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -416,13 +416,13 @@ static u8 __init get_vtl(void)
>  {
>  	u64 control = HV_HYPERCALL_REP_COMP_1 | HVCALL_GET_VP_REGISTERS;
>  	struct hv_input_get_vp_registers *input;
> -	struct hv_register_assoc *output;
> +	struct hv_get_vp_registers_output *output;
>  	unsigned long flags;
>  	u64 ret;
>  
>  	local_irq_save(flags);
>  	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
> -	output = (struct hv_register_assoc *)input;
> +	output = (struct hv_get_vp_registers_output *)input;
>  
>  	memset(input, 0, struct_size(input, names, 1));
>  	input->partition_id = HV_PARTITION_ID_SELF;
> @@ -432,7 +432,7 @@ static u8 __init get_vtl(void)
>  
>  	ret = hv_do_hypercall(control, input, output);
>  	if (hv_result_success(ret)) {
> -		ret = output->value.reg8 & HV_X64_VTL_MASK;
> +		ret = output->as64.low & HV_X64_VTL_MASK;
>  	} else {
>  		pr_err("Failed to get VTL(error: %lld) exiting...\n", ret);
>  		BUG();
> diff --git a/include/hyperv/hvgdk_mini.h b/include/hyperv/hvgdk_mini.h
> index db3d1aaf7330..0b1a10828f33 100644
> --- a/include/hyperv/hvgdk_mini.h
> +++ b/include/hyperv/hvgdk_mini.h
> @@ -1107,7 +1107,6 @@ union hv_register_value {
>  	union hv_x64_pending_interruption_register pending_interruption;
>  };
>  
> -#if defined(CONFIG_ARM64)
>  /* HvGetVpRegisters returns an array of these output elements */
>  struct hv_get_vp_registers_output {
>  	union {
> @@ -1124,8 +1123,6 @@ struct hv_get_vp_registers_output {
>  	};
>  };
>  
> -#endif /* CONFIG_ARM64 */
> -
>  struct hv_register_assoc {
>  	u32 name;			/* enum hv_register_name */
>  	u32 reserved1;