[PATCH v4] Drivers: hv: move panic report code from vmbus to hv early init code

From: longli
Date: Thu Apr 20 2023 - 18:50:09 EST

From: Long Li <longli@xxxxxxxxxxxxx>

The panic reporting code was added in commit 81b18bce48af
("Drivers: HV: Send one page worth of kmsg dump over Hyper-V during panic")

It was added to the vmbus driver. The panic reporting has no dependence
on vmbus, and can be enabled at an earlier boot time when Hyper-V is
initialized.

This patch moves the panic reporting code out of vmbus. There is no
functionality changes. During moving, also refactored some cleanup
functions into hv_kmsg_dump_unregister().

Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>

---
Change log v4:
1. Rebase to hyperv-next

Change log v3:
1. Rebase to linux-next

Change log v2:
1. Check on hv_is_isolation_supported() before reporting crash dump
2. Remove hyperv_report_reg(), inline the check condition instead
3. Remove the test NULL on hv_panic_page when freeing it

drivers/hv/hv.c | 36 -------
drivers/hv/hv_common.c | 231 +++++++++++++++++++++++++++++++++++++++++
drivers/hv/vmbus_drv.c | 199 -----------------------------------
3 files changed, 231 insertions(+), 235 deletions(-)

diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 4e1407d59ba0..de6708dbe0df 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -38,42 +38,6 @@ int hv_init(void)
return 0;
}

-/*
- * Functions for allocating and freeing memory with size and
- * alignment HV_HYP_PAGE_SIZE. These functions are needed because
- * the guest page size may not be the same as the Hyper-V page
- * size. We depend upon kmalloc() aligning power-of-two size
- * allocations to the allocation size boundary, so that the
- * allocated memory appears to Hyper-V as a page of the size
- * it expects.
- */
-
-void *hv_alloc_hyperv_page(void)
-{
- BUILD_BUG_ON(PAGE_SIZE < HV_HYP_PAGE_SIZE);
-
- if (PAGE_SIZE == HV_HYP_PAGE_SIZE)
- return (void *)__get_free_page(GFP_KERNEL);
- else
- return kmalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL);
-}
-
-void *hv_alloc_hyperv_zeroed_page(void)
-{
- if (PAGE_SIZE == HV_HYP_PAGE_SIZE)
- return (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
- else
- return kzalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL);
-}
-
-void hv_free_hyperv_page(unsigned long addr)
-{
- if (PAGE_SIZE == HV_HYP_PAGE_SIZE)
- free_page(addr);
- else
- kfree((void *)addr);
-}
-
/*
* hv_post_message - Post a message using the hypervisor message IPC.
*
diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index 6d40b6c7b23b..64f9ceca887b 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c
@@ -17,8 +17,11 @@
#include <linux/export.h>
#include <linux/bitfield.h>
#include <linux/cpumask.h>
+#include <linux/sched/task_stack.h>
#include <linux/panic_notifier.h>
#include <linux/ptrace.h>
+#include <linux/kdebug.h>
+#include <linux/kmsg_dump.h>
#include <linux/slab.h>
#include <linux/dma-map-ops.h>
#include <asm/hyperv-tlfs.h>
@@ -54,6 +57,10 @@ EXPORT_SYMBOL_GPL(hyperv_pcpu_input_arg);
void * __percpu *hyperv_pcpu_output_arg;
EXPORT_SYMBOL_GPL(hyperv_pcpu_output_arg);

+static void hv_kmsg_dump_unregister(void);
+
+static struct ctl_table_header *hv_ctl_table_hdr;
+
/*
* Hyper-V specific initialization and shutdown code that is
* common across all architectures. Called from architecture
@@ -62,6 +69,12 @@ EXPORT_SYMBOL_GPL(hyperv_pcpu_output_arg);

void __init hv_common_free(void)
{
+ unregister_sysctl_table(hv_ctl_table_hdr);
+ hv_ctl_table_hdr = NULL;
+
+ if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE)
+ hv_kmsg_dump_unregister();
+
kfree(hv_vp_index);
hv_vp_index = NULL;

@@ -72,10 +85,203 @@ void __init hv_common_free(void)
hyperv_pcpu_input_arg = NULL;
}

+/*
+ * Functions for allocating and freeing memory with size and
+ * alignment HV_HYP_PAGE_SIZE. These functions are needed because
+ * the guest page size may not be the same as the Hyper-V page
+ * size. We depend upon kmalloc() aligning power-of-two size
+ * allocations to the allocation size boundary, so that the
+ * allocated memory appears to Hyper-V as a page of the size
+ * it expects.
+ */
+
+void *hv_alloc_hyperv_page(void)
+{
+ BUILD_BUG_ON(PAGE_SIZE < HV_HYP_PAGE_SIZE);
+
+ if (PAGE_SIZE == HV_HYP_PAGE_SIZE)
+ return (void *)__get_free_page(GFP_KERNEL);
+ else
+ return kmalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL);
+}
+EXPORT_SYMBOL_GPL(hv_alloc_hyperv_page);
+
+void *hv_alloc_hyperv_zeroed_page(void)
+{
+ if (PAGE_SIZE == HV_HYP_PAGE_SIZE)
+ return (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
+ else
+ return kzalloc(HV_HYP_PAGE_SIZE, GFP_KERNEL);
+}
+EXPORT_SYMBOL_GPL(hv_alloc_hyperv_zeroed_page);
+
+void hv_free_hyperv_page(unsigned long addr)
+{
+ if (PAGE_SIZE == HV_HYP_PAGE_SIZE)
+ free_page(addr);
+ else
+ kfree((void *)addr);
+}
+EXPORT_SYMBOL_GPL(hv_free_hyperv_page);
+
+static void *hv_panic_page;
+
+/*
+ * Boolean to control whether to report panic messages over Hyper-V.
+ *
+ * It can be set via /proc/sys/kernel/hyperv_record_panic_msg
+ */
+static int sysctl_record_panic_msg = 1;
+
+/*
+ * sysctl option to allow the user to control whether kmsg data should be
+ * reported to Hyper-V on panic.
+ */
+static struct ctl_table hv_ctl_table[] = {
+ {
+ .procname = "hyperv_record_panic_msg",
+ .data = &sysctl_record_panic_msg,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = SYSCTL_ZERO,
+ .extra2 = SYSCTL_ONE
+ },
+ {}
+};
+
+static int hv_die_panic_notify_crash(struct notifier_block *self,
+ unsigned long val, void *args);
+
+static struct notifier_block hyperv_die_report_block = {
+ .notifier_call = hv_die_panic_notify_crash,
+};
+
+static struct notifier_block hyperv_panic_report_block = {
+ .notifier_call = hv_die_panic_notify_crash,
+};
+
+/*
+ * The following callback works both as die and panic notifier; its
+ * goal is to provide panic information to the hypervisor unless the
+ * kmsg dumper is used [see hv_kmsg_dump()], which provides more
+ * information but isn't always available.
+ *
+ * Notice that both the panic/die report notifiers are registered only
+ * if we have the capability HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE set.
+ */
+static int hv_die_panic_notify_crash(struct notifier_block *self,
+ unsigned long val, void *args)
+{
+ struct pt_regs *regs;
+ bool is_die;
+
+ /* Don't notify Hyper-V unless we have a die oops event or panic. */
+ if (self == &hyperv_panic_report_block) {
+ is_die = false;
+ regs = current_pt_regs();
+ } else { /* die event */
+ if (val != DIE_OOPS)
+ return NOTIFY_DONE;
+
+ is_die = true;
+ regs = ((struct die_args *)args)->regs;
+ }
+
+ /*
+ * Hyper-V should be notified only once about a panic/die. If we will
+ * be calling hv_kmsg_dump() later with kmsg data, don't do the
+ * notification here.
+ */
+ if (!sysctl_record_panic_msg || !hv_panic_page)
+ hyperv_report_panic(regs, val, is_die);
+
+ return NOTIFY_DONE;
+}
+
+/*
+ * Callback from kmsg_dump. Grab as much as possible from the end of the kmsg
+ * buffer and call into Hyper-V to transfer the data.
+ */
+static void hv_kmsg_dump(struct kmsg_dumper *dumper,
+ enum kmsg_dump_reason reason)
+{
+ struct kmsg_dump_iter iter;
+ size_t bytes_written;
+
+ /* We are only interested in panics. */
+ if (reason != KMSG_DUMP_PANIC || !sysctl_record_panic_msg)
+ return;
+
+ /*
+ * Write dump contents to the page. No need to synchronize; panic should
+ * be single-threaded.
+ */
+ kmsg_dump_rewind(&iter);
+ kmsg_dump_get_buffer(&iter, false, hv_panic_page, HV_HYP_PAGE_SIZE,
+ &bytes_written);
+ if (!bytes_written)
+ return;
+ /*
+ * P3 to contain the physical address of the panic page & P4 to
+ * contain the size of the panic data in that page. Rest of the
+ * registers are no-op when the NOTIFY_MSG flag is set.
+ */
+ hv_set_register(HV_REGISTER_CRASH_P0, 0);
+ hv_set_register(HV_REGISTER_CRASH_P1, 0);
+ hv_set_register(HV_REGISTER_CRASH_P2, 0);
+ hv_set_register(HV_REGISTER_CRASH_P3, virt_to_phys(hv_panic_page));
+ hv_set_register(HV_REGISTER_CRASH_P4, bytes_written);
+
+ /*
+ * Let Hyper-V know there is crash data available along with
+ * the panic message.
+ */
+ hv_set_register(HV_REGISTER_CRASH_CTL,
+ (HV_CRASH_CTL_CRASH_NOTIFY |
+ HV_CRASH_CTL_CRASH_NOTIFY_MSG));
+}
+
+static struct kmsg_dumper hv_kmsg_dumper = {
+ .dump = hv_kmsg_dump,
+};
+
+static void hv_kmsg_dump_unregister(void)
+{
+ kmsg_dump_unregister(&hv_kmsg_dumper);
+ unregister_die_notifier(&hyperv_die_report_block);
+ atomic_notifier_chain_unregister(&panic_notifier_list,
+ &hyperv_panic_report_block);
+
+ hv_free_hyperv_page((unsigned long)hv_panic_page);
+ hv_panic_page = NULL;
+}
+
+static void hv_kmsg_dump_register(void)
+{
+ int ret;
+
+ hv_panic_page = hv_alloc_hyperv_zeroed_page();
+ if (!hv_panic_page) {
+ pr_err("Hyper-V: panic message page memory allocation failed\n");
+ return;
+ }
+
+ ret = kmsg_dump_register(&hv_kmsg_dumper);
+ if (ret) {
+ pr_err("Hyper-V: kmsg dump register error 0x%x\n", ret);
+ hv_free_hyperv_page((unsigned long)hv_panic_page);
+ hv_panic_page = NULL;
+ }
+}
+
int __init hv_common_init(void)
{
int i;

+ if (hv_is_isolation_supported())
+ sysctl_record_panic_msg = 0;
+
/*
* Hyper-V expects to get crash register data or kmsg when
* crash enlightment is available and system crashes. Set
@@ -84,8 +290,33 @@ int __init hv_common_init(void)
* kernel.
*/
if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
+ u64 hyperv_crash_ctl;
+
crash_kexec_post_notifiers = true;
pr_info("Hyper-V: enabling crash_kexec_post_notifiers\n");
+
+ /*
+ * Panic message recording (sysctl_record_panic_msg)
+ * is enabled by default in non-isolated guests and
+ * disabled by default in isolated guests; the panic
+ * message recording won't be available in isolated
+ * guests should the following registration fail.
+ */
+ hv_ctl_table_hdr = register_sysctl("kernel", hv_ctl_table);
+ if (!hv_ctl_table_hdr)
+ pr_err("Hyper-V: sysctl table register error");
+
+ /*
+ * Register for panic kmsg callback only if the right
+ * capability is supported by the hypervisor.
+ */
+ hyperv_crash_ctl = hv_get_register(HV_REGISTER_CRASH_CTL);
+ if (hyperv_crash_ctl & HV_CRASH_CTL_CRASH_NOTIFY_MSG)
+ hv_kmsg_dump_register();
+
+ register_die_notifier(&hyperv_die_report_block);
+ atomic_notifier_chain_register(&panic_notifier_list,
+ &hyperv_panic_report_block);
}

/*
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 19a0069dc4a9..309c78ce1d30 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -30,7 +30,6 @@
#include <linux/panic_notifier.h>
#include <linux/ptrace.h>
#include <linux/screen_info.h>
-#include <linux/kdebug.h>
#include <linux/efi.h>
#include <linux/random.h>
#include <linux/kernel.h>
@@ -50,26 +49,12 @@ static struct device *hv_dev;

static int hyperv_cpuhp_online;

-static void *hv_panic_page;
-
static long __percpu *vmbus_evt;

/* Values parsed from ACPI DSDT */
int vmbus_irq;
int vmbus_interrupt;

-/*
- * Boolean to control whether to report panic messages over Hyper-V.
- *
- * It can be set via /proc/sys/kernel/hyperv_record_panic_msg
- */
-static int sysctl_record_panic_msg = 1;
-
-static int hyperv_report_reg(void)
-{
- return !sysctl_record_panic_msg || !hv_panic_page;
-}
-
/*
* The panic notifier below is responsible solely for unloading the
* vmbus connection, which is necessary in a panic event.
@@ -90,54 +75,6 @@ static struct notifier_block hyperv_panic_vmbus_unload_block = {
.priority = INT_MIN + 1, /* almost the latest one to execute */
};

-static int hv_die_panic_notify_crash(struct notifier_block *self,
- unsigned long val, void *args);
-
-static struct notifier_block hyperv_die_report_block = {
- .notifier_call = hv_die_panic_notify_crash,
-};
-static struct notifier_block hyperv_panic_report_block = {
- .notifier_call = hv_die_panic_notify_crash,
-};
-
-/*
- * The following callback works both as die and panic notifier; its
- * goal is to provide panic information to the hypervisor unless the
- * kmsg dumper is used [see hv_kmsg_dump()], which provides more
- * information but isn't always available.
- *
- * Notice that both the panic/die report notifiers are registered only
- * if we have the capability HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE set.
- */
-static int hv_die_panic_notify_crash(struct notifier_block *self,
- unsigned long val, void *args)
-{
- struct pt_regs *regs;
- bool is_die;
-
- /* Don't notify Hyper-V unless we have a die oops event or panic. */
- if (self == &hyperv_panic_report_block) {
- is_die = false;
- regs = current_pt_regs();
- } else { /* die event */
- if (val != DIE_OOPS)
- return NOTIFY_DONE;
-
- is_die = true;
- regs = ((struct die_args *)args)->regs;
- }
-
- /*
- * Hyper-V should be notified only once about a panic/die. If we will
- * be calling hv_kmsg_dump() later with kmsg data, don't do the
- * notification here.
- */
- if (hyperv_report_reg())
- hyperv_report_panic(regs, val, is_die);
-
- return NOTIFY_DONE;
-}
-
static const char *fb_mmio_name = "fb_range";
static struct resource *fb_mmio;
static struct resource *hyperv_mmio;
@@ -1379,98 +1316,6 @@ static irqreturn_t vmbus_percpu_isr(int irq, void *dev_id)
return IRQ_HANDLED;
}

-/*
- * Callback from kmsg_dump. Grab as much as possible from the end of the kmsg
- * buffer and call into Hyper-V to transfer the data.
- */
-static void hv_kmsg_dump(struct kmsg_dumper *dumper,
- enum kmsg_dump_reason reason)
-{
- struct kmsg_dump_iter iter;
- size_t bytes_written;
-
- /* We are only interested in panics. */
- if ((reason != KMSG_DUMP_PANIC) || (!sysctl_record_panic_msg))
- return;
-
- /*
- * Write dump contents to the page. No need to synchronize; panic should
- * be single-threaded.
- */
- kmsg_dump_rewind(&iter);
- kmsg_dump_get_buffer(&iter, false, hv_panic_page, HV_HYP_PAGE_SIZE,
- &bytes_written);
- if (!bytes_written)
- return;
- /*
- * P3 to contain the physical address of the panic page & P4 to
- * contain the size of the panic data in that page. Rest of the
- * registers are no-op when the NOTIFY_MSG flag is set.
- */
- hv_set_register(HV_REGISTER_CRASH_P0, 0);
- hv_set_register(HV_REGISTER_CRASH_P1, 0);
- hv_set_register(HV_REGISTER_CRASH_P2, 0);
- hv_set_register(HV_REGISTER_CRASH_P3, virt_to_phys(hv_panic_page));
- hv_set_register(HV_REGISTER_CRASH_P4, bytes_written);
-
- /*
- * Let Hyper-V know there is crash data available along with
- * the panic message.
- */
- hv_set_register(HV_REGISTER_CRASH_CTL,
- (HV_CRASH_CTL_CRASH_NOTIFY | HV_CRASH_CTL_CRASH_NOTIFY_MSG));
-}
-
-static struct kmsg_dumper hv_kmsg_dumper = {
- .dump = hv_kmsg_dump,
-};
-
-static void hv_kmsg_dump_register(void)
-{
- int ret;
-
- hv_panic_page = hv_alloc_hyperv_zeroed_page();
- if (!hv_panic_page) {
- pr_err("Hyper-V: panic message page memory allocation failed\n");
- return;
- }
-
- ret = kmsg_dump_register(&hv_kmsg_dumper);
- if (ret) {
- pr_err("Hyper-V: kmsg dump register error 0x%x\n", ret);
- hv_free_hyperv_page((unsigned long)hv_panic_page);
- hv_panic_page = NULL;
- }
-}
-
-static struct ctl_table_header *hv_ctl_table_hdr;
-
-/*
- * sysctl option to allow the user to control whether kmsg data should be
- * reported to Hyper-V on panic.
- */
-static struct ctl_table hv_ctl_table[] = {
- {
- .procname = "hyperv_record_panic_msg",
- .data = &sysctl_record_panic_msg,
- .maxlen = sizeof(int),
- .mode = 0644,
- .proc_handler = proc_dointvec_minmax,
- .extra1 = SYSCTL_ZERO,
- .extra2 = SYSCTL_ONE
- },
- {}
-};
-
-static struct ctl_table hv_root_table[] = {
- {
- .procname = "kernel",
- .mode = 0555,
- .child = hv_ctl_table
- },
- {}
-};
-
/*
* vmbus_bus_init -Main vmbus driver initialization routine.
*
@@ -1534,38 +1379,6 @@ static int vmbus_bus_init(void)
if (ret)
goto err_connect;

- if (hv_is_isolation_supported())
- sysctl_record_panic_msg = 0;
-
- /*
- * Only register if the crash MSRs are available
- */
- if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
- u64 hyperv_crash_ctl;
- /*
- * Panic message recording (sysctl_record_panic_msg)
- * is enabled by default in non-isolated guests and
- * disabled by default in isolated guests; the panic
- * message recording won't be available in isolated
- * guests should the following registration fail.
- */
- hv_ctl_table_hdr = register_sysctl_table(hv_root_table);
- if (!hv_ctl_table_hdr)
- pr_err("Hyper-V: sysctl table register error");
-
- /*
- * Register for panic kmsg callback only if the right
- * capability is supported by the hypervisor.
- */
- hyperv_crash_ctl = hv_get_register(HV_REGISTER_CRASH_CTL);
- if (hyperv_crash_ctl & HV_CRASH_CTL_CRASH_NOTIFY_MSG)
- hv_kmsg_dump_register();
-
- register_die_notifier(&hyperv_die_report_block);
- atomic_notifier_chain_register(&panic_notifier_list,
- &hyperv_panic_report_block);
- }
-
/*
* Always register the vmbus unload panic notifier because we
* need to shut the VMbus channel connection on panic.
@@ -1590,8 +1403,6 @@ static int vmbus_bus_init(void)
}
err_setup:
bus_unregister(&hv_bus);
- unregister_sysctl_table(hv_ctl_table_hdr);
- hv_ctl_table_hdr = NULL;
return ret;
}

@@ -2887,13 +2698,6 @@ static void __exit vmbus_exit(void)
vmbus_free_channels();
kfree(vmbus_connection.channels);

- if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
- kmsg_dump_unregister(&hv_kmsg_dumper);
- unregister_die_notifier(&hyperv_die_report_block);
- atomic_notifier_chain_unregister(&panic_notifier_list,
- &hyperv_panic_report_block);
- }
-
/*
* The vmbus panic notifier is always registered, hence we should
* also unconditionally unregister it here as well.
@@ -2901,9 +2705,6 @@ static void __exit vmbus_exit(void)
atomic_notifier_chain_unregister(&panic_notifier_list,
&hyperv_panic_vmbus_unload_block);

- free_page((unsigned long)hv_panic_page);
- unregister_sysctl_table(hv_ctl_table_hdr);
- hv_ctl_table_hdr = NULL;
bus_unregister(&hv_bus);

cpuhp_remove_state(hyperv_cpuhp_online);
--
2.32.0