linux-kernel - Re: [PATCH v6 5/5] hyperv: Do not overlap the hvcall IO areas in hv_vtl_apicid_to_vp

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Message-ID: <63865d43-1d26-48aa-a033-3f9b464fbc66@linux.microsoft.com>
Date: Wed, 8 Jan 2025 15:34:50 -0800
From: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
To: Roman Kisel <romank@...ux.microsoft.com>, hpa@...or.com,
 kys@...rosoft.com, bp@...en8.de, dave.hansen@...ux.intel.com,
 decui@...rosoft.com, eahariha@...ux.microsoft.com, haiyangz@...rosoft.com,
 mingo@...hat.com, mhklinux@...look.com, tglx@...utronix.de,
 tiala@...rosoft.com, wei.liu@...nel.org, linux-hyperv@...r.kernel.org,
 linux-kernel@...r.kernel.org, x86@...nel.org
Cc: apais@...rosoft.com, benhill@...rosoft.com, ssengar@...rosoft.com,
 sunilmut@...rosoft.com, vdso@...bites.dev
Subject: Re: [PATCH v6 5/5] hyperv: Do not overlap the hvcall IO areas in
 hv_vtl_apicid_to_vp_id()

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@...look.com>
> Closes: https://lore.kernel.org/lkml/SN6PR02MB4157B98CD34781CC87A9D921D40D2@SN6PR02MB4157.namprd02.prod.outlook.com/
> Signed-off-by: Roman Kisel <romank@...ux.microsoft.com>
> Reviewed-by: Easwar Hariharan <eahariha@...ux.microsoft.com>
> ---
>  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@...ux.microsoft.com>