linux-kernel - Re: [PATCH v3 3/5] hyperv: Enable the hypercall output page for the VTL mode

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Message-ID: <ded7fedc-b420-46c6-ba33-5c2f1cb4831e@linux.microsoft.com>
Date: Thu, 26 Dec 2024 13:42:35 -0800
From: Easwar Hariharan <eahariha@...ux.microsoft.com>
To: Roman Kisel <romank@...ux.microsoft.com>
Cc: hpa@...or.com, kys@...rosoft.com, bp@...en8.de,
 dave.hansen@...ux.intel.com, decui@...rosoft.com, haiyangz@...rosoft.com,
 mingo@...hat.com, mhklinux@...look.com, nunodasneves@...ux.microsoft.com,
 tglx@...utronix.de, tiala@...rosoft.com, wei.liu@...nel.org,
 linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org, x86@...nel.org,
 eahariha@...ux.microsoft.com, apais@...rosoft.com, benhill@...rosoft.com,
 ssengar@...rosoft.com, sunilmut@...rosoft.com, vdso@...bites.dev
Subject: Re: [PATCH v3 3/5] hyperv: Enable the hypercall output page for the
 VTL mode

On 12/26/2024 1:31 PM, Roman Kisel wrote:
> Due to the hypercall page not being allocated in the VTL mode,
> the code resorts to using a part of the input page.
> 
> Allocate the hypercall output page in the VTL mode thus enabling
> it to use it for output and share code with dom0.
> 
> Signed-off-by: Roman Kisel <romank@...ux.microsoft.com>
> ---
>  drivers/hv/hv_common.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> index c4fd07d9bf1a..5178beed6ca8 100644
> --- a/drivers/hv/hv_common.c
> +++ b/drivers/hv/hv_common.c
> @@ -340,7 +340,7 @@ int __init hv_common_init(void)
>  	BUG_ON(!hyperv_pcpu_input_arg);
>  
>  	/* Allocate the per-CPU state for output arg for root */
> -	if (hv_root_partition) {
> +	if (hv_root_partition || IS_ENABLED(CONFIG_HYPERV_VTL_MODE)) {
>  		hyperv_pcpu_output_arg = alloc_percpu(void *);
>  		BUG_ON(!hyperv_pcpu_output_arg);
>  	}
> @@ -435,7 +435,7 @@ int hv_common_cpu_init(unsigned int cpu)
>  	void **inputarg, **outputarg;
>  	u64 msr_vp_index;
>  	gfp_t flags;
> -	int pgcount = hv_root_partition ? 2 : 1;
> +	const int pgcount = (hv_root_partition || IS_ENABLED(CONFIG_HYPERV_VTL_MODE)) ? 2 : 1;
>  	void *mem;
>  	int ret;

Thanks for the const!

Reviewed-by: Easwar Hariharan <eahariha@...ux.microsoft.com>