Re: [PATCH v5 07/10] Drivers: hv: Introduce per-cpu event ring tail

---
 drivers/hv/hv_common.c | 34 ++++++++++++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index 252fd66ad4db..2763cb6d3678 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c

@@ -68,6 +68,16 @@ static void hv_kmsg_dump_unregister(void);

 static struct ctl_table_header *hv_ctl_table_hdr;

+/*
+ * Per-cpu array holding the tail pointer for the SynIC event ring buffer
+ * for each SINT.
+ *
+ * We cannot maintain this in mshv driver because the tail pointer should
+ * persist even if the mshv driver is unloaded.
+ */
+u8 __percpu **hv_synic_eventring_tail;
+EXPORT_SYMBOL_GPL(hv_synic_eventring_tail);
+
 /*
  * Hyper-V specific initialization and shutdown code that is
  * common across all architectures.  Called from architecture

@@ -90,6 +100,9 @@ void __init hv_common_free(void)

        free_percpu(hyperv_pcpu_input_arg);
        hyperv_pcpu_input_arg = NULL;
+
+       free_percpu(hv_synic_eventring_tail);
+       hv_synic_eventring_tail = NULL;
 }

 /*

@@ -372,6 +385,11 @@ int __init hv_common_init(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);
+       }
+
        hv_vp_index = kmalloc_array(nr_cpu_ids, sizeof(*hv_vp_index),
                                    GFP_KERNEL);
        if (!hv_vp_index) {

@@ -460,6 +478,7 @@ void __init ms_hyperv_late_init(void)
 int hv_common_cpu_init(unsigned int cpu)
 {
        void **inputarg, **outputarg;
+       u8 **synic_eventring_tail;
        u64 msr_vp_index;
        gfp_t flags;
        const int pgcount = hv_output_page_exists() ? 2 : 1;

@@ -472,8 +491,8 @@ int hv_common_cpu_init(unsigned int cpu)
        inputarg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);

        /*
-        * hyperv_pcpu_input_arg and hyperv_pcpu_output_arg memory is already
-        * allocated if this CPU was previously online and then taken offline
+        * The per-cpu memory is already allocated if this CPU was previously
+        * online and then taken offline
         */
        if (!*inputarg) {
                mem = kmalloc(pgcount * HV_HYP_PAGE_SIZE, flags);

@@ -485,6 +504,17 @@ int hv_common_cpu_init(unsigned int cpu)
                        *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);
+
+                       if (unlikely(!*synic_eventring_tail)) {
+                               kfree(mem);
+                               return -ENOMEM;
+                       }
+               }
+
                if (!ms_hyperv.paravisor_present &&
                    (hv_isolation_type_snp() || hv_isolation_type_tdx())) {
                        ret = set_memory_decrypted((unsigned long)mem, pgcount);
--

2.34.1