Re: [PATCH v6 5/5] hyperv: Do not overlap the hvcall IO areas in hv_vtl_apicid_to_vp_id()

[Nuno Das Neves]

On 1/8/2025 2:21 PM, Roman Kisel wrote:
> The Top-Level Functional Specification for Hyper-V, Section 3.6 [1, 2],
> disallows overlapping of the input and output hypercall areas, and
> hv_vtl_apicid_to_vp_id() overlaps them.
> 
> Use the output hypercall page of the current vCPU for the hypercall.
> 
> [1] https://learn.microsoft.com/en-us/virtualization/hyper-v-on-windows/tlfs/hypercall-interface
> [2] https://github.com/MicrosoftDocs/Virtualization-Documentation/tree/main/tlfs
> 
> Reported-by: Michael Kelley <mhklinux@xxxxxxxxxxx>
> Closes: https://lore.kernel.org/lkml/SN6PR02MB4157B98CD34781CC87A9D921D40D2@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
> Signed-off-by: Roman Kisel <romank@xxxxxxxxxxxxxxxxxxx>
> Reviewed-by: Easwar Hariharan <eahariha@xxxxxxxxxxxxxxxxxxx>
> ---
>  arch/x86/hyperv/hv_vtl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c
> index 04775346369c..4e1b1e3b5658 100644
> --- a/arch/x86/hyperv/hv_vtl.c
> +++ b/arch/x86/hyperv/hv_vtl.c
> @@ -189,7 +189,7 @@ static int hv_vtl_apicid_to_vp_id(u32 apic_id)
>  	input->partition_id = HV_PARTITION_ID_SELF;
>  	input->apic_ids[0] = apic_id;
>  
> -	output = (u32 *)input;
> +	output = *this_cpu_ptr(hyperv_pcpu_output_arg);
>  
>  	control = HV_HYPERCALL_REP_COMP_1 | HVCALL_GET_VP_ID_FROM_APIC_ID;
>  	status = hv_do_hypercall(control, input, output);

Reviewed-by: Nuno Das Neves <nunodasneves@xxxxxxxxxxxxxxxxxxx>