linux-kernel - Re: [PATCH 1/6] mshv: Only map vp->vp_stats

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Message-ID: <e18af534-cf48-4e0b-8a14-37268dfc2c80@gmail.com>
Date: Fri, 5 Sep 2025 10:20:39 -0500
From: Praveen K Paladugu <praveenkpaladugu@...il.com>
To: Nuno Das Neves <nunodasneves@...ux.microsoft.com>,
 linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
 mhklinux@...look.com, decui@...rosoft.com, paekkaladevi@...ux.microsoft.com
Subject: Re: [PATCH 1/6] mshv: Only map vp->vp_stats_pages if on root
 scheduler



On 8/28/2025 7:43 PM, Nuno Das Neves wrote:
> This mapping is only used for checking if the dispatch thread is
> blocked. This is only relevant for the root scheduler, so check the
> scheduler type to determine whether to map/unmap these pages, instead of
> the current check, which is incorrect.
> 
> Signed-off-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
> ---
>   drivers/hv/mshv_root_main.c | 12 ++++++++----
>   1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
> index e4ee9beddaf5..bbdefe8a2e9c 100644
> --- a/drivers/hv/mshv_root_main.c
> +++ b/drivers/hv/mshv_root_main.c
> @@ -987,7 +987,11 @@ mshv_partition_ioctl_create_vp(struct mshv_partition *partition,
>   			goto unmap_register_page;
>   	}
>   
> -	if (hv_parent_partition()) {
> +	/*
> +	 * This mapping of the stats page is for detecting if dispatch thread
> +	 * is blocked - only relevant for root scheduler
> +	 */
> +	if (hv_scheduler_type == HV_SCHEDULER_TYPE_ROOT) {
>   		ret = mshv_vp_stats_map(partition->pt_id, args.vp_index,
>   					stats_pages);
>   		if (ret)
> @@ -1016,7 +1020,7 @@ mshv_partition_ioctl_create_vp(struct mshv_partition *partition,
>   	if (mshv_partition_encrypted(partition) && is_ghcb_mapping_available())
>   		vp->vp_ghcb_page = page_to_virt(ghcb_page);
>   
> -	if (hv_parent_partition())
> +	if (hv_scheduler_type == HV_SCHEDULER_TYPE_ROOT)
>   		memcpy(vp->vp_stats_pages, stats_pages, sizeof(stats_pages));
>   
>   	/*
> @@ -1039,7 +1043,7 @@ mshv_partition_ioctl_create_vp(struct mshv_partition *partition,
>   free_vp:
>   	kfree(vp);
>   unmap_stats_pages:
> -	if (hv_parent_partition())
> +	if (hv_scheduler_type == HV_SCHEDULER_TYPE_ROOT)
>   		mshv_vp_stats_unmap(partition->pt_id, args.vp_index);
>   unmap_ghcb_page:
>   	if (mshv_partition_encrypted(partition) && is_ghcb_mapping_available()) {
> @@ -1793,7 +1797,7 @@ static void destroy_partition(struct mshv_partition *partition)
>   			if (!vp)
>   				continue;
>   
> -			if (hv_parent_partition())
> +			if (hv_scheduler_type == HV_SCHEDULER_TYPE_ROOT)
>   				mshv_vp_stats_unmap(partition->pt_id, vp->vp_index);
>   
>   			if (vp->vp_register_page) {

Reviewed-by: Praveen K Paladugu <prapal@...ux.microsoft.com>