From: Purna Pavan Chandra Aekkaladevi <[email protected]>

Older versions of the hypervisor do not support HV_STATS_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 
<[email protected]>
Signed-off-by: Nuno Das Neves <[email protected]>
Reviewed-by: Stanislav Kinsburskii <[email protected]>
---
 drivers/hv/mshv_root_hv_call.c | 41 ++++++++++++++++++++++++++++++----
 drivers/hv/mshv_root_main.c    |  3 +++
 2 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/drivers/hv/mshv_root_hv_call.c b/drivers/hv/mshv_root_hv_call.c
index 598eaff4ff29..b1770c7b500c 100644
--- a/drivers/hv/mshv_root_hv_call.c
+++ b/drivers/hv/mshv_root_hv_call.c
@@ -855,6 +855,24 @@ static int hv_call_map_stats_page2(enum 
hv_stats_object_type type,
        return ret;
 }
 
+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;
+}
+
 static int hv_call_map_stats_page(enum hv_stats_object_type type,
                                  const union hv_stats_object_identity 
*identity,
                                  void **addr)
@@ -863,7 +881,7 @@ static int hv_call_map_stats_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);
@@ -878,11 +896,26 @@ static int hv_call_map_stats_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;
+
+                       /*
+                        * Older versions of the hypervisor do not support the
+                        * PARENT stats area. In this case return "success" but
+                        * set the page to NULL. The caller should check for
+                        * this case and instead just use the SELF area.
+                        */
+                       if (hv_stats_get_area_type(type, identity) == 
HV_STATS_AREA_PARENT &&
+                           hv_status == HV_STATUS_INVALID_PARAMETER) {
+                               *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 bc15d6f6922f..f59a4ab47685 100644
--- a/drivers/hv/mshv_root_main.c
+++ b/drivers/hv/mshv_root_main.c
@@ -905,6 +905,9 @@ 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


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