From: longli@xxxxxxxxxxxxxxxxx <longli@xxxxxxxxxxxxxxxxx> Sent: Monday, April 10, 2023 7:10 PM
>
> 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(), and removed unused function
> hv_alloc_hyperv_page().
>
> Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
> ---
> drivers/hv/hv.c | 36 ------
> drivers/hv/hv_common.c | 227 +++++++++++++++++++++++++++++++++
> drivers/hv/vmbus_drv.c | 186 ---------------------------
> include/asm-generic/mshyperv.h | 1 -
> 4 files changed, 227 insertions(+), 223 deletions(-)
>
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index 8b0dd8e5244d..88eca08c7030 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 52a6f89ccdbd..d696c2110349 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;
>
> @@ -72,6 +85,195 @@ 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_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;
> +static int sysctl_record_panic_msg = 1;
> +
> +static int hyperv_report_reg(void)
> +{
> + return !sysctl_record_panic_msg || !hv_panic_page;
> +}
Nit: The above function is used in only one place. The code could
easily just go inline. Putting the code inline would probably be
clearer anyway.
> +
> +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;
> +}
> +
> +/*
> + * 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);
> +
> + if (hv_panic_page) {
No need to explicitly test for NULL. hv_free_hyperv_page() handles that
case already.
> + 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;
> + }
> +}
> +
> +/*
> + * 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
> + },
> + {}
> +};
> +
> int __init hv_common_init(void)
> {
> int i;
> @@ -84,8 +286,33 @@ 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_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);
> }
>
> /*
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index d24dd65b33d4..96fb596ab68f 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -28,7 +28,6 @@
> #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>
> @@ -63,11 +62,6 @@ int vmbus_interrupt;
> */
> 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.
> @@ -88,54 +82,6 @@ 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;
> @@ -1377,98 +1323,6 @@ 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.
> *
> @@ -1535,35 +1389,6 @@ static int vmbus_bus_init(void)
> if (hv_is_isolation_supported())
> sysctl_record_panic_msg = 0;
The above two lines of code should move as well. Otherwise we have a
window during early boot where the panic message might be dumped
to the Hyper-V host in a CVM.
>
> - /*
> - * 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.
> @@ -1588,8 +1413,6 @@ 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;
> }
>
> @@ -2818,13 +2641,6 @@ 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.
> @@ -2833,8 +2649,6 @@ static void __exit vmbus_exit(void)
> &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);
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> index 8845a2eca339..df0dbccd719a 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -186,7 +186,6 @@ void __init hv_common_free(void);
> int hv_common_cpu_init(unsigned int cpu);
> int hv_common_cpu_die(unsigned int cpu);
>
> -void *hv_alloc_hyperv_page(void);
> void *hv_alloc_hyperv_zeroed_page(void);
> void hv_free_hyperv_page(unsigned long addr);
>
> --
> 2.32.0
