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Message-ID:
<SN6PR02MB4157C65BAC4AB4315606F521D490A@SN6PR02MB4157.namprd02.prod.outlook.com>
Date: Tue, 27 Jan 2026 16:57:05 +0000
From: Michael Kelley <mhklinux@...look.com>
To: Nuno Das Neves <nunodasneves@...ux.microsoft.com>,
"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"skinsburskii@...ux.microsoft.com" <skinsburskii@...ux.microsoft.com>
CC: "kys@...rosoft.com" <kys@...rosoft.com>, "haiyangz@...rosoft.com"
<haiyangz@...rosoft.com>, "wei.liu@...nel.org" <wei.liu@...nel.org>,
"decui@...rosoft.com" <decui@...rosoft.com>, "longli@...rosoft.com"
<longli@...rosoft.com>, "prapal@...ux.microsoft.com"
<prapal@...ux.microsoft.com>, "mrathor@...ux.microsoft.com"
<mrathor@...ux.microsoft.com>, "paekkaladevi@...ux.microsoft.com"
<paekkaladevi@...ux.microsoft.com>
Subject: RE: [PATCH v5 3/7] mshv: Improve mshv_vp_stats_map/unmap(), add them
to mshv_root.h
From: Nuno Das Neves <nunodasneves@...ux.microsoft.com> Sent: Monday, January 26, 2026 12:56 PM
>
> From: Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>
>
> These functions are currently only used to map child partition VP stats,
> on root partition. However, they will soon be used on L1VH, and and also
Duplicate word "and".
Remember to run checkpatch.pl over your patches -- this duplicate
word was flagged by checkpatch.
Michael
> used for mapping the host's own VP stats.
>
> Introduce a helper is_l1vh_parent() to determine whether we are mapping
> our own VP stats. In this case, do not attempt to map the PARENT area.
> Note this is a different case than mapping PARENT on an older hypervisor
> where it is not available at all, so must be handled separately.
>
> On unmap, pass the stats pages since on L1VH the kernel allocates them
> and they must be freed in hv_unmap_stats_page().
>
> Signed-off-by: Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>
> Signed-off-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
> ---
> drivers/hv/mshv_root.h | 10 ++++++
> drivers/hv/mshv_root_main.c | 61 ++++++++++++++++++++++++++-----------
> 2 files changed, 54 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/hv/mshv_root.h b/drivers/hv/mshv_root.h
> index 05ba1f716f9e..e4912b0618fa 100644
> --- a/drivers/hv/mshv_root.h
> +++ b/drivers/hv/mshv_root.h
> @@ -254,6 +254,16 @@ struct mshv_partition *mshv_partition_get(struct
> mshv_partition *partition);
> void mshv_partition_put(struct mshv_partition *partition);
> struct mshv_partition *mshv_partition_find(u64 partition_id) __must_hold(RCU);
>
> +static inline bool is_l1vh_parent(u64 partition_id)
> +{
> + return hv_l1vh_partition() && (partition_id == HV_PARTITION_ID_SELF);
> +}
> +
> +int mshv_vp_stats_map(u64 partition_id, u32 vp_index,
> + struct hv_stats_page **stats_pages);
> +void mshv_vp_stats_unmap(u64 partition_id, u32 vp_index,
> + struct hv_stats_page **stats_pages);
> +
> /* hypercalls */
>
> int hv_call_withdraw_memory(u64 count, int node, u64 partition_id);
> diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
> index be5ad0fbfbee..faca3cc63e79 100644
> --- a/drivers/hv/mshv_root_main.c
> +++ b/drivers/hv/mshv_root_main.c
> @@ -956,23 +956,36 @@ mshv_vp_release(struct inode *inode, struct file *filp)
> return 0;
> }
>
> -static void mshv_vp_stats_unmap(u64 partition_id, u32 vp_index,
> - struct hv_stats_page *stats_pages[])
> +void mshv_vp_stats_unmap(u64 partition_id, u32 vp_index,
> + struct hv_stats_page *stats_pages[])
> {
> union hv_stats_object_identity identity = {
> .vp.partition_id = partition_id,
> .vp.vp_index = vp_index,
> };
> + int err;
>
> identity.vp.stats_area_type = HV_STATS_AREA_SELF;
> - hv_unmap_stats_page(HV_STATS_OBJECT_VP, NULL, &identity);
> -
> - identity.vp.stats_area_type = HV_STATS_AREA_PARENT;
> - hv_unmap_stats_page(HV_STATS_OBJECT_VP, NULL, &identity);
> + err = hv_unmap_stats_page(HV_STATS_OBJECT_VP,
> + stats_pages[HV_STATS_AREA_SELF],
> + &identity);
> + if (err)
> + pr_err("%s: failed to unmap partition %llu vp %u self stats, err: %d\n",
> + __func__, partition_id, vp_index, err);
> +
> + if (stats_pages[HV_STATS_AREA_PARENT] !=
> stats_pages[HV_STATS_AREA_SELF]) {
> + identity.vp.stats_area_type = HV_STATS_AREA_PARENT;
> + err = hv_unmap_stats_page(HV_STATS_OBJECT_VP,
> + stats_pages[HV_STATS_AREA_PARENT],
> + &identity);
> + if (err)
> + pr_err("%s: failed to unmap partition %llu vp %u parent stats,
> err: %d\n",
> + __func__, partition_id, vp_index, err);
> + }
> }
>
> -static int mshv_vp_stats_map(u64 partition_id, u32 vp_index,
> - struct hv_stats_page *stats_pages[])
> +int mshv_vp_stats_map(u64 partition_id, u32 vp_index,
> + struct hv_stats_page *stats_pages[])
> {
> union hv_stats_object_identity identity = {
> .vp.partition_id = partition_id,
> @@ -983,23 +996,37 @@ static int mshv_vp_stats_map(u64 partition_id, u32
> vp_index,
> identity.vp.stats_area_type = HV_STATS_AREA_SELF;
> err = hv_map_stats_page(HV_STATS_OBJECT_VP, &identity,
> &stats_pages[HV_STATS_AREA_SELF]);
> - if (err)
> + if (err) {
> + pr_err("%s: failed to map partition %llu vp %u self stats, err: %d\n",
> + __func__, partition_id, vp_index, err);
> return err;
> + }
>
> - identity.vp.stats_area_type = HV_STATS_AREA_PARENT;
> - err = hv_map_stats_page(HV_STATS_OBJECT_VP, &identity,
> - &stats_pages[HV_STATS_AREA_PARENT]);
> - if (err)
> - goto unmap_self;
> -
> - if (!stats_pages[HV_STATS_AREA_PARENT])
> + /*
> + * L1VH partition cannot access its vp stats in parent area.
> + */
> + if (is_l1vh_parent(partition_id)) {
> stats_pages[HV_STATS_AREA_PARENT] =
> stats_pages[HV_STATS_AREA_SELF];
> + } else {
> + identity.vp.stats_area_type = HV_STATS_AREA_PARENT;
> + err = hv_map_stats_page(HV_STATS_OBJECT_VP, &identity,
> + &stats_pages[HV_STATS_AREA_PARENT]);
> + if (err) {
> + pr_err("%s: failed to map partition %llu vp %u parent stats, err:
> %d\n",
> + __func__, partition_id, vp_index, err);
> + goto unmap_self;
> + }
> + if (!stats_pages[HV_STATS_AREA_PARENT])
> + stats_pages[HV_STATS_AREA_PARENT] =
> stats_pages[HV_STATS_AREA_SELF];
> + }
>
> return 0;
>
> unmap_self:
> identity.vp.stats_area_type = HV_STATS_AREA_SELF;
> - hv_unmap_stats_page(HV_STATS_OBJECT_VP, NULL, &identity);
> + hv_unmap_stats_page(HV_STATS_OBJECT_VP,
> + stats_pages[HV_STATS_AREA_SELF],
> + &identity);
> return err;
> }
>
> --
> 2.34.1
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