[Xen-devel] [PATCH 2/2 v2] xen/acpi: upload PM state from init-domain to Xen

[Ankur Arora <ankur.a.arora@xxxxxxxxxx>]

This was broken in commit cd979883b9ede90643e019f33cb317933eb867b4.
do_suspend (from xen/manage.c) and thus xen_resume_notifier never get
called on the initial-domain at resume (it is if running as guest.)

The rationale for the breaking change was that upload_pm_data()
potentially does blocking work in syscore_resume(). This patch
addresses the original issue by scheduling upload_pm_data() to
execute in workqueue context.

Changes in v2:
 - rebased to 4.11.0-rc2
 - addressed comments from Boris Ostrovsky

Cc: Stanislaw Gruszka <sgruszka@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Based-on-patch-by: Konrad Wilk <konrad.wilk@xxxxxxxxxx>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Signed-off-by: Ankur Arora <ankur.a.arora@xxxxxxxxxx>
---
 drivers/xen/xen-acpi-processor.c | 34 ++++++++++++++++++++++++++--------
 1 file changed, 26 insertions(+), 8 deletions(-)

diff --git a/drivers/xen/xen-acpi-processor.c b/drivers/xen/xen-acpi-processor.c
index fac0d7b..23e391d 100644
--- a/drivers/xen/xen-acpi-processor.c
+++ b/drivers/xen/xen-acpi-processor.c
@@ -27,10 +27,10 @@
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/types.h>
+#include <linux/syscore_ops.h>
 #include <linux/acpi.h>
 #include <acpi/processor.h>
 #include <xen/xen.h>
-#include <xen/xen-ops.h>
 #include <xen/interface/platform.h>
 #include <asm/xen/hypercall.h>
 
@@ -466,15 +466,33 @@ static int xen_upload_processor_pm_data(void)
        return rc;
 }
 
-static int xen_acpi_processor_resume(struct notifier_block *nb,
-                                    unsigned long action, void *data)
+static void xen_acpi_processor_resume_worker(struct work_struct *dummy)
 {
+       int rc;
+
        bitmap_zero(acpi_ids_done, nr_acpi_bits);
-       return xen_upload_processor_pm_data();
+
+       rc = xen_upload_processor_pm_data();
+       if (rc != 0)
+               pr_info("ACPI data upload failed, error = %d\n", rc);
+}
+
+static void xen_acpi_processor_resume(void)
+{
+       static DECLARE_WORK(wq, xen_acpi_processor_resume_worker);
+
+       /*
+        * xen_upload_processor_pm_data() calls non-atomic code.
+        * However, the context for xen_acpi_processor_resume is syscore
+        * with only the boot CPU online and in an atomic context.
+        *
+        * So defer the upload for some point safer.
+        */
+       schedule_work(&wq);
 }
 
-struct notifier_block xen_acpi_processor_resume_nb = {
-       .notifier_call = xen_acpi_processor_resume,
+static struct syscore_ops xap_syscore_ops = {
+       .resume = xen_acpi_processor_resume,
 };
 
 static int __init xen_acpi_processor_init(void)
@@ -527,7 +545,7 @@ static int __init xen_acpi_processor_init(void)
        if (rc)
                goto err_unregister;
 
-       xen_resume_notifier_register(&xen_acpi_processor_resume_nb);
+       register_syscore_ops(&xap_syscore_ops);
 
        return 0;
 err_unregister:
@@ -544,7 +562,7 @@ static void __exit xen_acpi_processor_exit(void)
 {
        int i;
 
-       xen_resume_notifier_unregister(&xen_acpi_processor_resume_nb);
+       unregister_syscore_ops(&xap_syscore_ops);
        kfree(acpi_ids_done);
        kfree(acpi_id_present);
        kfree(acpi_id_cst_present);
-- 
2.7.4


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