On Fri, Aug 29, 2025 at 8:44 AM Nuno Das Neves
<nunodasne...@linux.microsoft.com> wrote:
>
> From: Purna Pavan Chandra Aekkaladevi <paekkalad...@linux.microsoft.com>
>
> Some versions of the hypervisor do not support HV_STATUS_AREA_PARENT and
> return HV_STATUS_INVALID_PARAMETER for the second stats page mapping
> request.
>
> This results a failure in module init. Instead of failing, gracefully
> fall back to populating stats_pages[HV_STATS_AREA_PARENT] with the
> already-mapped stats_pages[HV_STATS_AREA_SELF].
>
> Signed-off-by: Purna Pavan Chandra Aekkaladevi
> <paekkalad...@linux.microsoft.com>
> Signed-off-by: Nuno Das Neves <nunodasne...@linux.microsoft.com>
> ---
> drivers/hv/mshv_root_hv_call.c | 43 ++++++++++++++++++++++++++++++----
> drivers/hv/mshv_root_main.c | 3 +++
> 2 files changed, 42 insertions(+), 4 deletions(-)
>
Reviewed-by: Tianyu Lan <ti...@microsoft.com>
> diff --git a/drivers/hv/mshv_root_hv_call.c b/drivers/hv/mshv_root_hv_call.c
> index c9c274f29c3c..1c38576a673c 100644
> --- a/drivers/hv/mshv_root_hv_call.c
> +++ b/drivers/hv/mshv_root_hv_call.c
> @@ -724,6 +724,24 @@ hv_call_notify_port_ring_empty(u32 sint_index)
> return hv_result_to_errno(status);
> }
>
> +static int
> +hv_stats_get_area_type(enum hv_stats_object_type type,
> + const union hv_stats_object_identity *identity)
> +{
> + switch (type) {
> + case HV_STATS_OBJECT_HYPERVISOR:
> + return identity->hv.stats_area_type;
> + case HV_STATS_OBJECT_LOGICAL_PROCESSOR:
> + return identity->lp.stats_area_type;
> + case HV_STATS_OBJECT_PARTITION:
> + return identity->partition.stats_area_type;
> + case HV_STATS_OBJECT_VP:
> + return identity->vp.stats_area_type;
> + }
> +
> + return -EINVAL;
> +}
> +
> int hv_call_map_stat_page(enum hv_stats_object_type type,
> const union hv_stats_object_identity *identity,
> void **addr)
> @@ -732,7 +750,7 @@ int hv_call_map_stat_page(enum hv_stats_object_type type,
> struct hv_input_map_stats_page *input;
> struct hv_output_map_stats_page *output;
> u64 status, pfn;
> - int ret = 0;
> + int hv_status, ret = 0;
>
> do {
> local_irq_save(flags);
> @@ -747,11 +765,28 @@ int hv_call_map_stat_page(enum hv_stats_object_type
> type,
> pfn = output->map_location;
>
> local_irq_restore(flags);
> - if (hv_result(status) != HV_STATUS_INSUFFICIENT_MEMORY) {
> - ret = hv_result_to_errno(status);
> +
> + hv_status = hv_result(status);
> + if (hv_status != HV_STATUS_INSUFFICIENT_MEMORY) {
> if (hv_result_success(status))
> break;
> - return ret;
> +
> + /*
> + * Some versions of the hypervisor do not support the
> + * PARENT stats area. In this case return "success"
> but
> + * set the page to NULL. The caller checks for this
> + * case instead just uses the SELF area.
> + */
> + if (hv_stats_get_area_type(type, identity) ==
> HV_STATS_AREA_PARENT &&
> + hv_status == HV_STATUS_INVALID_PARAMETER) {
> + pr_debug_once("%s: PARENT area type is
> unsupported\n",
> + __func__);
> + *addr = NULL;
> + return 0;
> + }
> +
> + hv_status_debug(status, "\n");
> + return hv_result_to_errno(status);
> }
>
> ret = hv_call_deposit_pages(NUMA_NO_NODE,
> diff --git a/drivers/hv/mshv_root_main.c b/drivers/hv/mshv_root_main.c
> index bbdefe8a2e9c..56ababab57ce 100644
> --- a/drivers/hv/mshv_root_main.c
> +++ b/drivers/hv/mshv_root_main.c
> @@ -929,6 +929,9 @@ static int mshv_vp_stats_map(u64 partition_id, u32
> vp_index,
> if (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:
> --
> 2.34.1
>
>
--
Thanks
Tianyu Lan
