Re: [PATCH AUTOSEL 6.13 11/15] hyperv: Do not overlap the hvcall IO areas in hv_vtl_apicid_to_vp_id()

[Roman Kisel <romank@linux.microsoft.com>]

Hi Sasha,

The patch picked up for the stable tree will need this bit
"[PATCH v6 3/5] hyperv: Enable the hypercall output page for the VTL  mode"

https://lore.kernel.org/linux-hyperv/20250108222138.1623703-4-romank@linux.microsoft.com/

On 1/28/2025 9:53 AM, Sasha Levin wrote:
> From: Roman Kisel <romank@linux.microsoft.com>
> 
> [ Upstream commit f285d995743269aa9f893e5e9a1065604137c1f6 ]
> 
> 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@outlook.com>
> Closes: https://lore.kernel.org/lkml/SN6PR02MB4157B98CD34781CC87A9D921D40D2@SN6PR02MB4157.namprd02.prod.outlook.com/
> Signed-off-by: Roman Kisel <romank@linux.microsoft.com>
> Reviewed-by: Easwar Hariharan <eahariha@linux.microsoft.com>
> Reviewed-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
> Link: https://lore.kernel.org/r/20250108222138.1623703-6-romank@linux.microsoft.com
> Signed-off-by: Wei Liu <wei.liu@kernel.org>
> Message-ID: <20250108222138.1623703-6-romank@linux.microsoft.com>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>   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 04775346369c5..4e1b1e3b56584 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);

-- 
Thank you,
Roman