This is a more flexible approach for determining whether to allocate the
output page.

Signed-off-by: Nuno Das Neves <redacted>
Acked-by: Wei Liu <wei.liu@kernel.org>
---
 drivers/hv/hv_common.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index 39077841d518..3f6f23e4c579 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c

@@ -58,6 +58,14 @@ EXPORT_SYMBOL_GPL(hyperv_pcpu_input_arg);
 void * __percpu *hyperv_pcpu_output_arg;
 EXPORT_SYMBOL_GPL(hyperv_pcpu_output_arg);

+/*
+ * Determine whether output arg is needed
+ */
+static inline bool hv_output_arg_exists(void)
+{
+       return hv_root_partition ? true : false;
+}
+
 static void hv_kmsg_dump_unregister(void);

 static struct ctl_table_header *hv_ctl_table_hdr;

@@ -342,10 +350,12 @@ int __init hv_common_init(void)
        hyperv_pcpu_input_arg = alloc_percpu(void  *);
        BUG_ON(!hyperv_pcpu_input_arg);

-       /* Allocate the per-CPU state for output arg for root */
-       if (hv_root_partition) {
+       if (hv_output_arg_exists()) {
                hyperv_pcpu_output_arg = alloc_percpu(void *);
                BUG_ON(!hyperv_pcpu_output_arg);
+       }
+
+       if (hv_root_partition) {
                hv_synic_eventring_tail = alloc_percpu(u8 *);
                BUG_ON(hv_synic_eventring_tail == NULL);
        }

@@ -375,7 +385,7 @@ int hv_common_cpu_init(unsigned int cpu)
        u8 **synic_eventring_tail;
        u64 msr_vp_index;
        gfp_t flags;
-       int pgcount = hv_root_partition ? 2 : 1;
+       int pgcount = hv_output_arg_exists() ? 2 : 1;
        void *mem;
        int ret;

@@ -393,9 +403,12 @@ int hv_common_cpu_init(unsigned int cpu)
                if (!mem)
                        return -ENOMEM;

-               if (hv_root_partition) {
+               if (hv_output_arg_exists()) {
                        outputarg = (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
                        *outputarg = (char *)mem + HV_HYP_PAGE_SIZE;
+               }
+
+               if (hv_root_partition) {
                        synic_eventring_tail = (u8 **)this_cpu_ptr(hv_synic_eventring_tail);
                        *synic_eventring_tail = kcalloc(HV_SYNIC_SINT_COUNT, sizeof(u8),
                                                        flags);
--

2.25.1