linux-kernel - Re: [PATCH 2/3] mshv: handle gpa intercepts for arm64

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Message-ID: <aUGElRga1r2g8cb-@skinsburskii.localdomain>
Date: Tue, 16 Dec 2025 08:11:01 -0800
From: Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>
To: Anirudh Rayabharam <anirudh@...rudhrb.com>
Cc: kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
	decui@...rosoft.com, longli@...rosoft.com,
	linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] mshv: handle gpa intercepts for arm64

On Tue, Dec 16, 2025 at 02:20:29PM +0000, Anirudh Rayabharam wrote:
> From: Anirudh Rayabharam (Microsoft) <anirudh@...rudhrb.com>
> 
> The mshv driver now uses movable pages for guests. For arm64 guests
> to be functional, handle gpa intercepts for arm64 too (the current
> code implements handling only for x86). Without this, arm64 guests are
> broken.
> 
> Move some arch-agnostic functions out of #ifdefs so that they can be
> re-used.
> 
> Signed-off-by: Anirudh Rayabharam (Microsoft) <anirudh@...rudhrb.com>
> ---
>  drivers/hv/mshv_root_main.c | 38 ++++++++++++++++++++++++++++---------
>  1 file changed, 29 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
> index 9cf28a3f12fe..882605349664 100644
> --- a/drivers/hv/mshv_root_main.c
> +++ b/drivers/hv/mshv_root_main.c
> @@ -608,7 +608,6 @@ mshv_partition_region_by_gfn(struct mshv_partition *partition, u64 gfn)
>  	return NULL;
>  }
>  
> -#ifdef CONFIG_X86_64
>  static struct mshv_mem_region *
>  mshv_partition_region_by_gfn_get(struct mshv_partition *p, u64 gfn)
>  {
> @@ -625,6 +624,34 @@ mshv_partition_region_by_gfn_get(struct mshv_partition *p, u64 gfn)
>  	return region;
>  }
>  
> +#ifdef CONFIG_X86_64
> +static u64 mshv_get_gpa_intercept_gfn(struct mshv_vp *vp)
> +{
> +	struct hv_x64_memory_intercept_message *msg;
> +	u64 gfn;
> +
> +	msg = (struct hv_x64_memory_intercept_message *)
> +		vp->vp_intercept_msg_page->u.payload;
> +
> +	gfn = HVPFN_DOWN(msg->guest_physical_address);
> +
> +	return gfn;
> +}
> +#else  /* CONFIG_X86_64 */

It's better to explicitly branch for ARM64 here for clarity as
hv_arm64_memory_intercept_message is defined only for ARM64.

> +static u64 mshv_get_gpa_intercept_gfn(struct mshv_vp *vp)
> +{
> +	struct hv_arm64_memory_intercept_message *msg;
> +	u64 gfn;
> +
> +	msg = (struct hv_arm64_memory_intercept_message *)
> +		vp->vp_intercept_msg_page->u.payload;
> +
> +	gfn = HVPFN_DOWN(msg->guest_physical_address);
> +
> +	return gfn;
> +}
> +#endif /* CONFIG_X86_64 */
> +

Are these functions really needed?
It would be clearer (and shorter) to branch directly in
mshv_handle_gpa_intercept.

Thanks,
Stanislav

>  /**
>   * mshv_handle_gpa_intercept - Handle GPA (Guest Physical Address) intercepts.
>   * @vp: Pointer to the virtual processor structure.
> @@ -640,14 +667,10 @@ static bool mshv_handle_gpa_intercept(struct mshv_vp *vp)
>  {
>  	struct mshv_partition *p = vp->vp_partition;
>  	struct mshv_mem_region *region;
> -	struct hv_x64_memory_intercept_message *msg;
>  	bool ret;
>  	u64 gfn;
>  
> -	msg = (struct hv_x64_memory_intercept_message *)
> -		vp->vp_intercept_msg_page->u.payload;
> -
> -	gfn = HVPFN_DOWN(msg->guest_physical_address);
> +	gfn = mshv_get_gpa_intercept_gfn(vp);
>  
>  	region = mshv_partition_region_by_gfn_get(p, gfn);
>  	if (!region)
> @@ -663,9 +686,6 @@ static bool mshv_handle_gpa_intercept(struct mshv_vp *vp)
>  
>  	return ret;
>  }
> -#else  /* CONFIG_X86_64 */
> -static bool mshv_handle_gpa_intercept(struct mshv_vp *vp) { return false; }
> -#endif /* CONFIG_X86_64 */
>  
>  static bool mshv_vp_handle_intercept(struct mshv_vp *vp)
>  {
> -- 
> 2.34.1
>