linux-kernel - Re: [PATCH v2 5/5] mshv: Introduce new hypercall to map stats page for L1VH partitions

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Message-ID: <949318ba-7623-42d2-90fd-0664915d994c@linux.microsoft.com>
Date: Thu, 11 Sep 2025 09:32:20 -0700
From: Easwar Hariharan <easwar.hariharan@...ux.microsoft.com>
To: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
Cc: linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
 prapal@...ux.microsoft.com, tiala@...rosoft.com, anirudh@...rudhrb.com,
 paekkaladevi@...ux.microsoft.com, easwar.hariharan@...ux.microsoft.com,
 kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
 decui@...rosoft.com, Jinank Jain <jinankjain@...ux.microsoft.com>
Subject: Re: [PATCH v2 5/5] mshv: Introduce new hypercall to map stats page
 for L1VH partitions

On 9/10/2025 4:14 PM, Nuno Das Neves wrote:
> From: Jinank Jain <jinankjain@...ux.microsoft.com>
> 
> Introduce HVCALL_MAP_STATS_PAGE2 which provides a map location (GPFN)
> to map the stats to. This hypercall is required for L1VH partitions,
> depending on the hypervisor version. This uses the same check as the
> state page map location; mshv_use_overlay_gpfn().
> 
> Add mshv_map_vp_state_page() helpers to use this new hypercall or the
> old one depending on availability.
> 
> For unmapping, the original HVCALL_UNMAP_STATS_PAGE works for both
> cases.
> 
> Signed-off-by: Jinank Jain <jinankjain@...ux.microsoft.com>
> Signed-off-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
> ---
>  drivers/hv/mshv_root.h         | 10 ++--
>  drivers/hv/mshv_root_hv_call.c | 89 ++++++++++++++++++++++++++++++++--
>  drivers/hv/mshv_root_main.c    | 25 ++++++----
>  include/hyperv/hvgdk_mini.h    |  1 +
>  include/hyperv/hvhdk_mini.h    |  7 +++
>  5 files changed, 112 insertions(+), 20 deletions(-)
> 
<snip>

> @@ -849,10 +850,13 @@ static void mshv_vp_stats_unmap(u64 partition_id, u32 vp_index)
>  	};
>  
>  	identity.vp.stats_area_type = HV_STATS_AREA_SELF;
> -	hv_call_unmap_stat_page(HV_STATS_OBJECT_VP, &identity);
> +	hv_unmap_stats_page(HV_STATS_OBJECT_VP, NULL, &identity);
> +
> +	if (stats_pages[HV_STATS_AREA_PARENT] == stats_pages[HV_STATS_AREA_SELF])
> +		return;

Nit, without patch 2, this hunk is a no-op. Despite that, looks good to me.

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

>  
>  	identity.vp.stats_area_type = HV_STATS_AREA_PARENT;
> -	hv_call_unmap_stat_page(HV_STATS_OBJECT_VP, &identity);
> +	hv_unmap_stats_page(HV_STATS_OBJECT_VP, NULL, &identity);
>  }

<snip>