diff mbox series

[v6,07/10] Drivers: hv: Introduce per-cpu event ring tail

Message ID 1741980536-3865-8-git-send-email-nunodasneves@linux.microsoft.com (mailing list archive)
State Handled Elsewhere, archived
Headers show
Series Introduce /dev/mshv root partition driver | expand

Commit Message

Nuno Das Neves March 14, 2025, 7:28 p.m. UTC 
Add a pointer hv_synic_eventring_tail to track the tail pointer for the
SynIC event ring buffer for each SINT.

This will be used by the mshv driver, but must be tracked independently
since the driver module could be removed and re-inserted.

Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
Reviewed-by: Wei Liu <wei.liu@kernel.org>
Reviewed-by: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
---
 drivers/hv/hv_common.c | 41 +++++++++++++++++++++++++++++++++++++----
 1 file changed, 37 insertions(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index 885bbc3d86d8..3cd9b96ffc67 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);
+	}
+
 	hv_vp_index = kmalloc_array(nr_cpu_ids, sizeof(*hv_vp_index),
 				    GFP_KERNEL);
 	if (!hv_vp_index) {
@@ -460,11 +478,12 @@  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;
 	void *mem;
-	int ret;
+	int ret = 0;
 
 	/* hv_cpu_init() can be called with IRQs disabled from hv_resume() */
 	flags = irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL;
@@ -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);
@@ -520,11 +539,21 @@  int hv_common_cpu_init(unsigned int cpu)
 	if (msr_vp_index > hv_max_vp_index)
 		hv_max_vp_index = msr_vp_index;
 
-	return 0;
+	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);
+		/* No need to unwind any of the above on failure here */
+		if (unlikely(!*synic_eventring_tail))
+			ret = -ENOMEM;
+	}
+
+	return ret;
 }
 
 int hv_common_cpu_die(unsigned int cpu)
 {
+	u8 **synic_eventring_tail;
 	/*
 	 * The hyperv_pcpu_input_arg and hyperv_pcpu_output_arg memory
 	 * is not freed when the CPU goes offline as the hyperv_pcpu_input_arg
@@ -537,6 +566,10 @@  int hv_common_cpu_die(unsigned int cpu)
 	 * originally allocated memory is reused in hv_common_cpu_init().
 	 */
 
+	synic_eventring_tail = this_cpu_ptr(hv_synic_eventring_tail);
+	kfree(*synic_eventring_tail);
+	*synic_eventring_tail = NULL;
+
 	return 0;
 }