[RFC PATCH v1 1/3] arm64/ras: support sea error recovery

From: Xie XiuQi
Date: Fri Sep 01 2017 - 06:32:03 EST

With ARM v8.2 RAS Extension, SEA are usually triggered when memory errors
are consumed. In some cases, if the error address is in a clean page or a
read-only page, there is a chance to recover. Such as error occurs in a
instruction page, we can reread this page from disk instead of killing process.

Because memory_failure() may sleep, we can not call it directly in SEA exception
context. So we saved faulting physical address associated with a process in the
ghes handler and set __TIF_SEA_NOTIFY. When we return from SEA exception context
and get into do_notify_resume() before the process running, we could check it
and call memory_failure() to do recovery. It's safe, because we are in process
context.

Signed-off-by: Xie XiuQi <xiexiuqi@xxxxxxxxxx>
Signed-off-by: Wang Xiongfeng <wangxiongfeng2@xxxxxxxxxx>
---
arch/arm64/Kconfig | 11 +++
arch/arm64/include/asm/ras.h | 27 +++++++
arch/arm64/include/asm/thread_info.h | 4 +-
arch/arm64/kernel/Makefile | 1 +
arch/arm64/kernel/ras.c | 138 +++++++++++++++++++++++++++++++++++
arch/arm64/kernel/signal.c | 8 ++
arch/arm64/mm/fault.c | 27 +++++--
drivers/acpi/apei/ghes.c | 2 +
8 files changed, 209 insertions(+), 9 deletions(-)
create mode 100644 arch/arm64/include/asm/ras.h
create mode 100644 arch/arm64/kernel/ras.c

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index dfd9086..7d44589 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -640,6 +640,17 @@ config HOTPLUG_CPU
Say Y here to experiment with turning CPUs off and on. CPUs
can be controlled through /sys/devices/system/cpu.

+config ARM64_ERR_RECOV
+ bool "Support arm64 RAS error recovery"
+ depends on ACPI_APEI_SEA && MEMORY_FAILURE
+ help
+ With ARM v8.2 RAS Extension, SEA are usually triggered when memory errors
+ are consumed. In some cases, if the error address is in a clean page or a
+ read-only page, there is a chance to recover. Such as error occurs in a
+ instruction page, we can reread this page from disk instead of killing process.
+
+ Say Y if unsure.
+
# Common NUMA Features
config NUMA
bool "Numa Memory Allocation and Scheduler Support"
diff --git a/arch/arm64/include/asm/ras.h b/arch/arm64/include/asm/ras.h
new file mode 100644
index 0000000..8c4f6a8
--- /dev/null
+++ b/arch/arm64/include/asm/ras.h
@@ -0,0 +1,27 @@
+/*
+ * ARM64 SEA error recoery support
+ *
+ * Copyright 2017 Huawei Technologies Co., Ltd.
+ * Author: Xie XiuQi <xiexiuqi@xxxxxxxxxx>
+ * Author: Wang Xiongfeng <wangxiongfeng2@xxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version
+ * 2 as published by the Free Software Foundation;
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef _ASM_RAS_H
+#define _ASM_RAS_H
+
+#include <linux/cper.h>
+#include <acpi/ghes.h>
+
+extern void sea_notify_process(void);
+extern void arm_proc_error_check(struct ghes *ghes, struct cper_sec_proc_arm *err);
+
+#endif /*_ASM_RAS_H*/
diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index 46c3b93..4b10131 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -86,6 +86,7 @@ struct thread_info {
#define TIF_NOTIFY_RESUME 2 /* callback before returning to user */
#define TIF_FOREIGN_FPSTATE 3 /* CPU's FP state is not current's */
#define TIF_UPROBE 4 /* uprobe breakpoint or singlestep */
+#define TIF_SEA_NOTIFY 5 /* notify to do an error recovery */
#define TIF_NOHZ 7
#define TIF_SYSCALL_TRACE 8
#define TIF_SYSCALL_AUDIT 9
@@ -102,6 +103,7 @@ struct thread_info {
#define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
#define _TIF_FOREIGN_FPSTATE (1 << TIF_FOREIGN_FPSTATE)
#define _TIF_NOHZ (1 << TIF_NOHZ)
+#define _TIF_SEA_NOTIFY (1 << TIF_SEA_NOTIFY)
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
#define _TIF_SYSCALL_TRACEPOINT (1 << TIF_SYSCALL_TRACEPOINT)
@@ -111,7 +113,7 @@ struct thread_info {

#define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
_TIF_NOTIFY_RESUME | _TIF_FOREIGN_FPSTATE | \
- _TIF_UPROBE)
+ _TIF_UPROBE|_TIF_SEA_NOTIFY)

#define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
_TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index f2b4e81..ba3abf8 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -43,6 +43,7 @@ arm64-obj-$(CONFIG_EFI) += efi.o efi-entry.stub.o
arm64-obj-$(CONFIG_PCI) += pci.o
arm64-obj-$(CONFIG_ARMV8_DEPRECATED) += armv8_deprecated.o
arm64-obj-$(CONFIG_ACPI) += acpi.o
+arm64-obj-$(CONFIG_ARM64_ERR_RECOV) += ras.o
arm64-obj-$(CONFIG_ACPI_NUMA) += acpi_numa.o
arm64-obj-$(CONFIG_ARM64_ACPI_PARKING_PROTOCOL) += acpi_parking_protocol.o
arm64-obj-$(CONFIG_PARAVIRT) += paravirt.o
diff --git a/arch/arm64/kernel/ras.c b/arch/arm64/kernel/ras.c
new file mode 100644
index 0000000..8562ec7
--- /dev/null
+++ b/arch/arm64/kernel/ras.c
@@ -0,0 +1,138 @@
+/*
+ * ARM64 SEA error recoery support
+ *
+ * Copyright 2017 Huawei Technologies Co., Ltd.
+ * Author: Xie XiuQi <xiexiuqi@xxxxxxxxxx>
+ * Author: Wang Xiongfeng <wangxiongfeng2@xxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version
+ * 2 as published by the Free Software Foundation;
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/cper.h>
+#include <linux/mm.h>
+#include <linux/preempt.h>
+#include <linux/acpi.h>
+#include <linux/sched/signal.h>
+
+#include <acpi/actbl1.h>
+#include <acpi/ghes.h>
+#include <acpi/apei.h>
+
+#include <asm/thread_info.h>
+#include <asm/atomic.h>
+#include <asm/ras.h>
+
+/*
+ * Need to save faulting physical address associated with a process
+ * in the sea ghes handler some place where we can grab it back
+ * later in sea_notify_process()
+ */
+#define SEA_INFO_MAX 16
+
+struct sea_info {
+ atomic_t inuse;
+ struct task_struct *t;
+ __u64 paddr;
+} sea_info[SEA_INFO_MAX];
+
+static int sea_save_info(__u64 addr)
+{
+ struct sea_info *si;
+
+ for (si = sea_info; si < &sea_info[SEA_INFO_MAX]; si++) {
+ if (atomic_cmpxchg(&si->inuse, 0, 1) == 0) {
+ si->t = current;
+ si->paddr = addr;
+ return 0;
+ }
+ }
+
+ pr_err("Too many concurrent recoverable errors\n");
+ return -ENOMEM;
+}
+
+static struct sea_info *sea_find_info(void)
+{
+ struct sea_info *si;
+
+ for (si = sea_info; si < &sea_info[SEA_INFO_MAX]; si++)
+ if (atomic_read(&si->inuse) && si->t == current)
+ return si;
+ return NULL;
+}
+
+static void sea_clear_info(struct sea_info *si)
+{
+ atomic_set(&si->inuse, 0);
+}
+
+/*
+ * Called in process context that interrupted by SEA and marked with
+ * TIF_SEA_NOTIFY, just before returning to erroneous userland.
+ * This code is allowed to sleep.
+ * Attempt possible recovery such as calling the high level VM handler to
+ * process any corrupted pages, and kill/signal current process if required.
+ * Action required errors are handled here.
+ */
+void sea_notify_process(void)
+{
+ unsigned long pfn;
+ int fail = 0, flags = MF_ACTION_REQUIRED;
+ struct sea_info *si = sea_find_info();
+
+ if (!si)
+ panic("Lost physical address for consumed uncorrectable error");
+
+ clear_thread_flag(TIF_SEA_NOTIFY);
+ do {
+ pfn = si->paddr >> PAGE_SHIFT;
+
+
+ pr_err("Uncorrected hardware memory error in user-access at %llx\n",
+ si->paddr);
+ /*
+ * We must call memory_failure() here even if the current process is
+ * doomed. We still need to mark the page as poisoned and alert any
+ * other users of the page.
+ */
+ if (memory_failure(pfn, 0, flags) < 0) {
+ fail++;
+ }
+ sea_clear_info(si);
+
+ si = sea_find_info();
+ } while (si);
+
+ if (fail) {
+ pr_err("Memory error not recovered\n");
+ force_sig(SIGBUS, current);
+ }
+}
+
+void arm_proc_error_check(struct ghes *ghes, struct cper_sec_proc_arm *err)
+{
+ int i, ret = -1;
+ struct cper_arm_err_info *err_info;
+
+ if ((ghes->generic->notify.type != ACPI_HEST_NOTIFY_SEA) ||
+ (ghes->estatus->error_severity != CPER_SEV_RECOVERABLE))
+ return;
+
+ err_info = (struct cper_arm_err_info *)(err + 1);
+ for (i = 0; i < err->err_info_num; i++, err_info++) {
+ if (err_info->validation_bits & CPER_ARM_INFO_VALID_PHYSICAL_ADDR) {
+ ret |= sea_save_info(err_info->physical_fault_addr);
+ }
+ }
+
+ if (!ret)
+ set_thread_flag(TIF_SEA_NOTIFY);
+}
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index 089c3747..71e314e 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -38,6 +38,7 @@
#include <asm/fpsimd.h>
#include <asm/signal32.h>
#include <asm/vdso.h>
+#include <asm/ras.h>

/*
* Do a signal return; undo the signal stack. These are aligned to 128-bit.
@@ -749,6 +750,13 @@ asmlinkage void do_notify_resume(struct pt_regs *regs,
* Update the trace code with the current status.
*/
trace_hardirqs_off();
+
+#ifdef CONFIG_ARM64_ERR_RECOV
+ /* notify userspace of pending SEAs */
+ if (thread_flags & _TIF_SEA_NOTIFY)
+ sea_notify_process();
+#endif /* CONFIG_ARM64_ERR_RECOV */
+
do {
if (thread_flags & _TIF_NEED_RESCHED) {
schedule();
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 1f22a41..b38476d 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -594,14 +594,25 @@ static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs)
nmi_exit();
}

- info.si_signo = SIGBUS;
- info.si_errno = 0;
- info.si_code = 0;
- if (esr & ESR_ELx_FnV)
- info.si_addr = NULL;
- else
- info.si_addr = (void __user *)addr;
- arm64_notify_die("", regs, &info, esr);
+ if (user_mode(regs)) {
+ if (test_thread_flag(TIF_SEA_NOTIFY))
+ return ret;
+
+ info.si_signo = SIGBUS;
+ info.si_errno = 0;
+ info.si_code = 0;
+ if (esr & ESR_ELx_FnV)
+ info.si_addr = NULL;
+ else
+ info.si_addr = (void __user *)addr;
+
+ current->thread.fault_address = 0;
+ current->thread.fault_code = esr;
+ force_sig_info(info.si_signo, &info, current);
+ } else {
+ die("Uncorrected hardware memory error in kernel-access\n",
+ regs, esr);
+ }

return ret;
}
diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index d661d45..fa9400d 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -52,6 +52,7 @@
#include <acpi/ghes.h>
#include <acpi/apei.h>
#include <asm/tlbflush.h>
+#include <asm/ras.h>
#include <ras/ras_event.h>

#include "apei-internal.h"
@@ -520,6 +521,7 @@ static void ghes_do_proc(struct ghes *ghes,
else if (guid_equal(sec_type, &CPER_SEC_PROC_ARM)) {
struct cper_sec_proc_arm *err = acpi_hest_get_payload(gdata);

+ arm_proc_error_check(ghes, err);
log_arm_hw_error(err);
} else {
void *err = acpi_hest_get_payload(gdata);
--
1.8.3.1