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

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Message-ID: <e1f9590f-4b81-4026-91c3-c4a48373fddc@linux.microsoft.com>
Date: Thu, 11 Sep 2025 11:00:16 -0700
From: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
To: Easwar Hariharan <easwar.hariharan@...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, 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 9/11/2025 9:32 AM, Easwar Hariharan wrote:
> 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.
> 
Ah, thanks - in fact it probably should have been in that patch instead of
this one in the first place.

> 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>