x86/mce: Provide a lockless memory pool to save error records

printk() is not safe to use in MCE context. Add a lockless
memory allocator pool to save error records in MCE context.
Those records will be issued later, in a printk-safe context.
The idea is inspired by the APEI/GHES driver.

We're very conservative and allocate only two pages for it but
since we're going to use those pages throughout the system's
lifetime, we allocate them statically to avoid early boot time
allocation woes.

Signed-off-by: Chen, Gong <gong.chen@linux.intel.com>
[ Rewrite. ]
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Link: http://lkml.kernel.org/r/1439396985-12812-3-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index b3a1a5d77d92c2fd1d1d1a3b0b0b898944e8cd5b..06dbb5da90c69fbc3df0f5e5e2b097c6f6185cc6 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -955,6 +955,7 @@ config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
 
 config X86_MCE
        bool "Machine Check / overheating reporting"
+       select GENERIC_ALLOCATOR
        default y
        ---help---
          Machine Check support allows the processor to notify the

diff --git a/arch/x86/kernel/cpu/mcheck/Makefile b/arch/x86/kernel/cpu/mcheck/Makefile
index bb34b03af25252ddb2298e80121f9955a6ae6192..a3311c88619463b005bcde39bd043d61dbf20954 100644 (file)
--- a/arch/x86/kernel/cpu/mcheck/Makefile
+++ b/arch/x86/kernel/cpu/mcheck/Makefile
@@ -1,4 +1,4 @@
-obj-y                          =  mce.o mce-severity.o
+obj-y                          =  mce.o mce-severity.o mce-genpool.o
 
 obj-$(CONFIG_X86_ANCIENT_MCE)  += winchip.o p5.o
 obj-$(CONFIG_X86_MCE_INTEL)    += mce_intel.o

diff --git a/arch/x86/kernel/cpu/mcheck/mce-genpool.c b/arch/x86/kernel/cpu/mcheck/mce-genpool.c
new file mode 100644 (file)
index 0000000..0a85010
--- /dev/null
+++ b/arch/x86/kernel/cpu/mcheck/mce-genpool.c
@@ -0,0 +1,99 @@
+/*
+ * MCE event pool management in MCE context
+ *
+ * Copyright (C) 2015 Intel Corp.
+ * Author: Chen, Gong <gong.chen@linux.intel.com>
+ *
+ * This file is licensed under GPLv2.
+ */
+#include <linux/smp.h>
+#include <linux/mm.h>
+#include <linux/genalloc.h>
+#include <linux/llist.h>
+#include "mce-internal.h"
+
+/*
+ * printk() is not safe in MCE context. This is a lock-less memory allocator
+ * used to save error information organized in a lock-less list.
+ *
+ * This memory pool is only to be used to save MCE records in MCE context.
+ * MCE events are rare, so a fixed size memory pool should be enough. Use
+ * 2 pages to save MCE events for now (~80 MCE records at most).
+ */
+#define MCE_POOLSZ     (2 * PAGE_SIZE)
+
+static struct gen_pool *mce_evt_pool;
+static LLIST_HEAD(mce_event_llist);
+static char gen_pool_buf[MCE_POOLSZ];
+
+void mce_gen_pool_process(void)
+{
+       struct llist_node *head;
+       struct mce_evt_llist *node;
+       struct mce *mce;
+
+       head = llist_del_all(&mce_event_llist);
+       if (!head)
+               return;
+
+       head = llist_reverse_order(head);
+       llist_for_each_entry(node, head, llnode) {
+               mce = &node->mce;
+               atomic_notifier_call_chain(&x86_mce_decoder_chain, 0, mce);
+               gen_pool_free(mce_evt_pool, (unsigned long)node, sizeof(*node));
+       }
+}
+
+bool mce_gen_pool_empty(void)
+{
+       return llist_empty(&mce_event_llist);
+}
+
+int mce_gen_pool_add(struct mce *mce)
+{
+       struct mce_evt_llist *node;
+
+       if (!mce_evt_pool)
+               return -EINVAL;
+
+       node = (void *)gen_pool_alloc(mce_evt_pool, sizeof(*node));
+       if (!node) {
+               pr_warn_ratelimited("MCE records pool full!\n");
+               return -ENOMEM;
+       }
+
+       memcpy(&node->mce, mce, sizeof(*mce));
+       llist_add(&node->llnode, &mce_event_llist);
+
+       return 0;
+}
+
+static int mce_gen_pool_create(void)
+{
+       struct gen_pool *tmpp;
+       int ret = -ENOMEM;
+
+       tmpp = gen_pool_create(ilog2(sizeof(struct mce_evt_llist)), -1);
+       if (!tmpp)
+               goto out;
+
+       ret = gen_pool_add(tmpp, (unsigned long)gen_pool_buf, MCE_POOLSZ, -1);
+       if (ret) {
+               gen_pool_destroy(tmpp);
+               goto out;
+       }
+
+       mce_evt_pool = tmpp;
+
+out:
+       return ret;
+}
+
+int mce_gen_pool_init(void)
+{
+       /* Just init mce_gen_pool once. */
+       if (mce_evt_pool)
+               return 0;
+
+       return mce_gen_pool_create();
+}

diff --git a/arch/x86/kernel/cpu/mcheck/mce-internal.h b/arch/x86/kernel/cpu/mcheck/mce-internal.h
index fe32074b865b1686ba9e0e2cdc3ccb5ebe99ddfe..ea8b62264c14708cdcf123a6b8af3dbfa75ffe22 100644 (file)
--- a/arch/x86/kernel/cpu/mcheck/mce-internal.h
+++ b/arch/x86/kernel/cpu/mcheck/mce-internal.h
@@ -13,6 +13,8 @@ enum severity_level {
        MCE_PANIC_SEVERITY,
 };
 
+extern struct atomic_notifier_head x86_mce_decoder_chain;
+
 #define ATTR_LEN               16
 #define INITIAL_CHECK_INTERVAL 5 * 60 /* 5 minutes */
 
@@ -24,6 +26,16 @@ struct mce_bank {
        char                    attrname[ATTR_LEN];     /* attribute name */
 };
 
+struct mce_evt_llist {
+       struct llist_node llnode;
+       struct mce mce;
+};
+
+void mce_gen_pool_process(void);
+bool mce_gen_pool_empty(void);
+int mce_gen_pool_add(struct mce *mce);
+int mce_gen_pool_init(void);
+
 extern int (*mce_severity)(struct mce *a, int tolerant, char **msg, bool is_excp);
 struct dentry *mce_get_debugfs_dir(void);
 

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index df919ff103c3ae845e727388765ebc1842df0cbc..a41c014e5cde9bcc133014e61a2c4f341618b5a7 100644 (file)
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -118,7 +118,7 @@ static void (*quirk_no_way_out)(int bank, struct mce *m, struct pt_regs *regs);
  * CPU/chipset specific EDAC code can register a notifier call here to print
  * MCE errors in a human-readable form.
  */
-static ATOMIC_NOTIFIER_HEAD(x86_mce_decoder_chain);
+ATOMIC_NOTIFIER_HEAD(x86_mce_decoder_chain);
 
 /* Do initial initialization of a struct mce */
 void mce_setup(struct mce *m)
@@ -1731,6 +1731,12 @@ void mcheck_cpu_init(struct cpuinfo_x86 *c)
                return;
        }
 
+       if (mce_gen_pool_init()) {
+               mca_cfg.disabled = true;
+               pr_emerg("Couldn't allocate MCE records pool!\n");
+               return;
+       }
+
        machine_check_vector = do_machine_check;
 
        __mcheck_cpu_init_generic();