Re: [PATCH RFC] RAS: hwerr_tracking: move recoverable hardware error tracking out of vmcoreinfo

[Bjorn Helgaas <helgaas@kernel.org>]

On Tue, Jul 07, 2026 at 07:02:34AM -0700, Breno Leitao wrote:
> The recoverable hardware error tracking (hwerr_log_error_type() and the
> hwerr_data[] counters) was added under vmcoreinfo, but it uses none of the
> vmcoreinfo note machinery: hwerr_data[] is a plain global array that crash
> tools read from the vmcore by symbol, like any other global.  Functionally
> it is RAS code, fed only by the hardware error paths (x86 MCE, APEI GHES
> and PCIe AER).
> 
> I wanted to expand it, and Baoquan suggested moving it away from vmcore
> info, which makes sense. [1]
> 
> Move the implementation to drivers/ras/hwerr_tracking.c and the
> declaration (with its no-op stub) to <linux/ras.h>.  Give it a dedicated
> CONFIG_RAS_HWERR (bool, under RAS, default y) rather than riding
> CONFIG_VMCORE_INFO, so it is a first-class RAS feature that can be turned
> off on its own.  The producers now reach hwerr_log_error_type() through
> <linux/ras.h>: x86 MCE and APEI GHES already include it, so drop their
> <linux/vmcore_info.h> include; PCIe AER switches its include from
> <linux/vmcore_info.h> to <linux/ras.h>.
> 
> enum hwerr_error_type stays in <uapi/linux/vmcore.h> as it has been part
> of the UAPI since the feature shipped; <linux/ras.h> includes it from
> there.
> 
> hwerr_data[] keeps its name and layout, so existing crash/drgn recipes
> keep working.  The config gate moves from CONFIG_VMCORE_INFO to
> CONFIG_RAS_HWERR (default y).
> 
> Link: https://lore.kernel.org/all/aYvi4Y_HNqk_u1-v@fedora/ [1]
> Signed-off-by: Breno Leitao <leitao@debian.org>
> ---
> Once we move it outside of vmcore info, I am planning to add new
> features that are in the limbo now, given they don't belong to vmcore
> info, such as:
> 
> Track fatal hardware errors
> 	https://lore.kernel.org/all/20260617-hwerr-v1-0-ff131cd6203c@debian.org/
> 
> Expose hardware error recovery statistics via sysfs
> 	https://lore.kernel.org/all/20260202-vmcoreinfo_sysfs-v2-0-8f3b5308b894@debian.org/
> ---
>  MAINTAINERS                    |  7 +++++++
>  arch/x86/kernel/cpu/mce/core.c |  1 -
>  drivers/acpi/apei/ghes.c       |  1 -
>  drivers/pci/pcie/aer.c         |  2 +-

Acked-by: Bjorn Helgaas <bhelgaas@google.com> # drivers/pci

>  drivers/ras/Kconfig            | 12 ++++++++++++
>  drivers/ras/Makefile           |  1 +
>  drivers/ras/hwerr_tracking.c   | 35 +++++++++++++++++++++++++++++++++++
>  include/linux/ras.h            |  7 +++++++
>  include/linux/vmcore_info.h    |  7 -------
>  kernel/vmcore_info.c           | 21 ---------------------
>  10 files changed, 63 insertions(+), 31 deletions(-)
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 1705eb823dd00..356a51032e4b0 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -22539,6 +22539,13 @@ L:	linux-edac@vger.kernel.org
>  S:	Maintained
>  F:	drivers/ras/amd/fmpm.c
>  
> +RAS RECOVERABLE HARDWARE ERROR TRACKING
> +M:	Breno Leitao <leitao@kernel.org>
> +L:	linux-edac@vger.kernel.org
> +S:	Maintained
> +F:	Documentation/driver-api/hw-recoverable-errors.rst
> +F:	drivers/ras/hwerr_tracking.c
> +
>  RASPBERRY PI PISP BACK END
>  M:	Jacopo Mondi <jacopo.mondi@ideasonboard.com>
>  R:	Raspberry Pi Kernel Maintenance <kernel-list@raspberrypi.com>
> diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
> index 9bba1e2f03af7..58f1d7a601883 100644
> --- a/arch/x86/kernel/cpu/mce/core.c
> +++ b/arch/x86/kernel/cpu/mce/core.c
> @@ -45,7 +45,6 @@
>  #include <linux/task_work.h>
>  #include <linux/hardirq.h>
>  #include <linux/kexec.h>
> -#include <linux/vmcore_info.h>
>  
>  #include <asm/fred.h>
>  #include <asm/cpu_device_id.h>
> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
> index 3236a3ce79d6b..4b6666bc19c77 100644
> --- a/drivers/acpi/apei/ghes.c
> +++ b/drivers/acpi/apei/ghes.c
> @@ -45,7 +45,6 @@
>  #include <linux/uuid.h>
>  #include <linux/ras.h>
>  #include <linux/task_work.h>
> -#include <linux/vmcore_info.h>
>  
>  #include <acpi/actbl1.h>
>  #include <acpi/ghes.h>
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index c4fd9c0b2a548..00cdca26a5114 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -30,7 +30,7 @@
>  #include <linux/kfifo.h>
>  #include <linux/ratelimit.h>
>  #include <linux/slab.h>
> -#include <linux/vmcore_info.h>
> +#include <linux/ras.h>
>  #include <acpi/apei.h>
>  #include <acpi/ghes.h>
>  #include <ras/ras_event.h>
> diff --git a/drivers/ras/Kconfig b/drivers/ras/Kconfig
> index fc4f4bb94a4c6..241642679c1f1 100644
> --- a/drivers/ras/Kconfig
> +++ b/drivers/ras/Kconfig
> @@ -34,6 +34,18 @@ if RAS
>  source "arch/x86/ras/Kconfig"
>  source "drivers/ras/amd/atl/Kconfig"
>  
> +config RAS_HWERR
> +	bool "Track hardware errors for crash analysis"
> +	default y
> +	help
> +	  Record the count and timestamp of the most recent recoverable
> +	  hardware error for each source (CPU, memory, PCI, CXL, ...).  The
> +	  data is written at runtime and read post-mortem from a vmcore by
> +	  tools such as crash or drgn, to correlate recoverable errors with a
> +	  later panic.
> +
> +	  If unsure, say Y.
> +
>  config RAS_FMPM
>  	tristate "FRU Memory Poison Manager"
>  	default m
> diff --git a/drivers/ras/Makefile b/drivers/ras/Makefile
> index 11f95d59d3972..4217bee75d910 100644
> --- a/drivers/ras/Makefile
> +++ b/drivers/ras/Makefile
> @@ -1,5 +1,6 @@
>  # SPDX-License-Identifier: GPL-2.0-only
>  obj-$(CONFIG_RAS)	+= ras.o
> +obj-$(CONFIG_RAS_HWERR)	+= hwerr_tracking.o
>  obj-$(CONFIG_DEBUG_FS)	+= debugfs.o
>  obj-$(CONFIG_RAS_CEC)	+= cec.o
>  
> diff --git a/drivers/ras/hwerr_tracking.c b/drivers/ras/hwerr_tracking.c
> new file mode 100644
> index 0000000000000..847c01fb24d55
> --- /dev/null
> +++ b/drivers/ras/hwerr_tracking.c
> @@ -0,0 +1,35 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Track recoverable hardware errors (visible to the OS but not fatal) so that
> + * crash tools like crash/drgn can read the count and timestamp of the last
> + * occurrence from a vmcore and correlate them with a subsequent panic.
> + *
> + * Copyright (c) 2026 Meta Platforms, Inc. and affiliates
> + * Copyright (c) 2026 Breno Leitao <leitao@kernel.org>
> + */
> +
> +#include <linux/atomic.h>
> +#include <linux/export.h>
> +#include <linux/ras.h>
> +#include <linux/timekeeping.h>
> +
> +struct hwerr_info {
> +	atomic_t count;
> +	time64_t timestamp;
> +};
> +
> +/*
> + * Keep hwerr_data[] at global scope so it stays accessible from the vmcore
> + * (via crash/drgn) even when Link Time Optimization (LTO) is enabled.
> + */
> +struct hwerr_info hwerr_data[HWERR_RECOV_MAX];
> +
> +void hwerr_log_error_type(enum hwerr_error_type src)
> +{
> +	if (src < 0 || src >= HWERR_RECOV_MAX)
> +		return;
> +
> +	atomic_inc(&hwerr_data[src].count);
> +	WRITE_ONCE(hwerr_data[src].timestamp, ktime_get_real_seconds());
> +}
> +EXPORT_SYMBOL_GPL(hwerr_log_error_type);
> diff --git a/include/linux/ras.h b/include/linux/ras.h
> index 468941bfe855f..1019183c00342 100644
> --- a/include/linux/ras.h
> +++ b/include/linux/ras.h
> @@ -5,6 +5,7 @@
>  #include <asm/errno.h>
>  #include <linux/uuid.h>
>  #include <linux/cper.h>
> +#include <uapi/linux/vmcore.h>
>  
>  #ifdef CONFIG_DEBUG_FS
>  int ras_userspace_consumers(void);
> @@ -35,6 +36,12 @@ static inline void
>  log_arm_hw_error(struct cper_sec_proc_arm *err, const u8 sev) { return; }
>  #endif
>  
> +#ifdef CONFIG_RAS_HWERR
> +void hwerr_log_error_type(enum hwerr_error_type src);
> +#else
> +static inline void hwerr_log_error_type(enum hwerr_error_type src) { }
> +#endif
> +
>  struct atl_err {
>  	u64 addr;
>  	u64 ipid;
> diff --git a/include/linux/vmcore_info.h b/include/linux/vmcore_info.h
> index e71518caacdfc..fb6f29b7202e3 100644
> --- a/include/linux/vmcore_info.h
> +++ b/include/linux/vmcore_info.h
> @@ -5,7 +5,6 @@
>  #include <linux/linkage.h>
>  #include <linux/elfcore.h>
>  #include <linux/elf.h>
> -#include <uapi/linux/vmcore.h>
>  
>  #define CRASH_CORE_NOTE_HEAD_BYTES ALIGN(sizeof(struct elf_note), 4)
>  #define CRASH_CORE_NOTE_NAME_BYTES ALIGN(sizeof(NN_PRSTATUS), 4)
> @@ -79,10 +78,4 @@ Elf_Word *append_elf_note(Elf_Word *buf, char *name, unsigned int type,
>  			  void *data, size_t data_len);
>  void final_note(Elf_Word *buf);
>  
> -#ifdef CONFIG_VMCORE_INFO
> -void hwerr_log_error_type(enum hwerr_error_type src);
> -#else
> -static inline void hwerr_log_error_type(enum hwerr_error_type src) {};
> -#endif
> -
>  #endif /* LINUX_VMCORE_INFO_H */
> diff --git a/kernel/vmcore_info.c b/kernel/vmcore_info.c
> index 8614430ca212a..5c288796bdbf5 100644
> --- a/kernel/vmcore_info.c
> +++ b/kernel/vmcore_info.c
> @@ -29,17 +29,6 @@ u32 *vmcoreinfo_note;
>  /* trusted vmcoreinfo, e.g. we can make a copy in the crash memory */
>  static unsigned char *vmcoreinfo_data_safecopy;
>  
> -struct hwerr_info {
> -	atomic_t count;
> -	time64_t timestamp;
> -};
> -
> -/*
> - * The hwerr_data[] array is declared with global scope so that it remains
> - * accessible to vmcoreinfo even when Link Time Optimization (LTO) is enabled.
> - */
> -struct hwerr_info hwerr_data[HWERR_RECOV_MAX];
> -
>  Elf_Word *append_elf_note(Elf_Word *buf, char *name, unsigned int type,
>  			  void *data, size_t data_len)
>  {
> @@ -127,16 +116,6 @@ phys_addr_t __weak paddr_vmcoreinfo_note(void)
>  }
>  EXPORT_SYMBOL(paddr_vmcoreinfo_note);
>  
> -void hwerr_log_error_type(enum hwerr_error_type src)
> -{
> -	if (src < 0 || src >= HWERR_RECOV_MAX)
> -		return;
> -
> -	atomic_inc(&hwerr_data[src].count);
> -	WRITE_ONCE(hwerr_data[src].timestamp, ktime_get_real_seconds());
> -}
> -EXPORT_SYMBOL_GPL(hwerr_log_error_type);
> -
>  static int __init crash_save_vmcoreinfo_init(void)
>  {
>  	int order;
> 
> ---
> base-commit: 3d5670d672ae08b8c534b7beed6f57c8b44e7b43
> change-id: 20260629-hwerr-ras-e26664926c58
> 
> Best regards,
> --  
> Breno Leitao <leitao@debian.org>
>