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Message-Id: <546d169211835aded@agluck-desk.sc.intel.com>
Date: Wed, 19 Nov 2014 14:15:46 -0800
From: "Luck, Tony" <tony.luck@...el.com>
To: Borislav Petkov <bp@...en8.de>, x86@...nel.org,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andy Lutomirski <luto@...capital.net>
Cc: linux-kernel@...r.kernel.org,
Peter Zijlstra <peterz@...radead.org>,
Oleg Nesterov <oleg@...hat.com>,
Tony Luck <tony.luck@...el.com>,
Andi Kleen <andi@...stfloor.org>
Subject: [PATCH] x86, mce: Get rid of TIF_MCE_NOTIFY and associated mce tricks
We now switch to the kernel stack when a machine check interrupts
during user mode. This means that we can perform recovery actions
in the tail of do_machine_check(). So say goodbye to TIF_MCE_NOTIFY,
mce_save_info(), mce_find_info() and mce_notify_process()
Signed-off-by: Tony Luck <tony.luck@...el.com>
---
Obviously this is dependent on Andy's patch series in
git://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git x86/paranoid
arch/x86/include/asm/mce.h | 1 -
arch/x86/include/asm/thread_info.h | 4 +-
arch/x86/kernel/cpu/mcheck/mce.c | 106 ++++++++-----------------------------
arch/x86/kernel/signal.c | 6 ---
4 files changed, 23 insertions(+), 94 deletions(-)
diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
index 958b90f761e5..be5a51a4a219 100644
--- a/arch/x86/include/asm/mce.h
+++ b/arch/x86/include/asm/mce.h
@@ -187,7 +187,6 @@ enum mcp_flags {
void machine_check_poll(enum mcp_flags flags, mce_banks_t *b);
int mce_notify_irq(void);
-void mce_notify_process(void);
DECLARE_PER_CPU(struct mce, injectm);
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 05701f132473..55a63f114a74 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -75,7 +75,6 @@ struct thread_info {
#define TIF_SYSCALL_EMU 6 /* syscall emulation active */
#define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */
#define TIF_SECCOMP 8 /* secure computing */
-#define TIF_MCE_NOTIFY 10 /* notify userspace of an MCE */
#define TIF_USER_RETURN_NOTIFY 11 /* notify kernel of userspace return */
#define TIF_UPROBE 12 /* breakpointed or singlestepping */
#define TIF_NOTSC 16 /* TSC is not accessible in userland */
@@ -100,7 +99,6 @@ struct thread_info {
#define _TIF_SYSCALL_EMU (1 << TIF_SYSCALL_EMU)
#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
#define _TIF_SECCOMP (1 << TIF_SECCOMP)
-#define _TIF_MCE_NOTIFY (1 << TIF_MCE_NOTIFY)
#define _TIF_USER_RETURN_NOTIFY (1 << TIF_USER_RETURN_NOTIFY)
#define _TIF_UPROBE (1 << TIF_UPROBE)
#define _TIF_NOTSC (1 << TIF_NOTSC)
@@ -140,7 +138,7 @@ struct thread_info {
/* Only used for 64 bit */
#define _TIF_DO_NOTIFY_MASK \
- (_TIF_SIGPENDING | _TIF_MCE_NOTIFY | _TIF_NOTIFY_RESUME | \
+ (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | \
_TIF_USER_RETURN_NOTIFY | _TIF_UPROBE)
/* flags to check in __switch_to() */
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 61a9668cebfd..66efc536f81d 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -956,51 +956,6 @@ static void mce_clear_state(unsigned long *toclear)
}
/*
- * Need to save faulting physical address associated with a process
- * in the machine check handler some place where we can grab it back
- * later in mce_notify_process()
- */
-#define MCE_INFO_MAX 16
-
-struct mce_info {
- atomic_t inuse;
- struct task_struct *t;
- __u64 paddr;
- int restartable;
-} mce_info[MCE_INFO_MAX];
-
-static void mce_save_info(__u64 addr, int c)
-{
- struct mce_info *mi;
-
- for (mi = mce_info; mi < &mce_info[MCE_INFO_MAX]; mi++) {
- if (atomic_cmpxchg(&mi->inuse, 0, 1) == 0) {
- mi->t = current;
- mi->paddr = addr;
- mi->restartable = c;
- return;
- }
- }
-
- mce_panic("Too many concurrent recoverable errors", NULL, NULL);
-}
-
-static struct mce_info *mce_find_info(void)
-{
- struct mce_info *mi;
-
- for (mi = mce_info; mi < &mce_info[MCE_INFO_MAX]; mi++)
- if (atomic_read(&mi->inuse) && mi->t == current)
- return mi;
- return NULL;
-}
-
-static void mce_clear_info(struct mce_info *mi)
-{
- atomic_set(&mi->inuse, 0);
-}
-
-/*
* The actual machine check handler. This only handles real
* exceptions when something got corrupted coming in through int 18.
*
@@ -1037,6 +992,8 @@ void do_machine_check(struct pt_regs *regs, long error_code)
DECLARE_BITMAP(toclear, MAX_NR_BANKS);
DECLARE_BITMAP(valid_banks, MAX_NR_BANKS);
char *msg = "Unknown";
+ u64 recover_paddr = ~0ull;
+ int flags = MF_ACTION_REQUIRED;
this_cpu_inc(mce_exception_count);
@@ -1155,9 +1112,9 @@ void do_machine_check(struct pt_regs *regs, long error_code)
if (no_way_out)
mce_panic("Fatal machine check on current CPU", &m, msg);
if (worst == MCE_AR_SEVERITY) {
- /* schedule action before return to userland */
- mce_save_info(m.addr, m.mcgstatus & MCG_STATUS_RIPV);
- set_thread_flag(TIF_MCE_NOTIFY);
+ recover_paddr = m.addr;
+ if (!(m.mcgstatus & MCG_STATUS_RIPV))
+ flags |= MF_MUST_KILL;
} else if (kill_it) {
force_sig(SIGBUS, current);
}
@@ -1168,6 +1125,23 @@ void do_machine_check(struct pt_regs *regs, long error_code)
mce_wrmsrl(MSR_IA32_MCG_STATUS, 0);
out:
sync_core();
+
+ if (recover_paddr == ~0ull)
+ return;
+
+ pr_err("Uncorrected hardware memory error in user-access at %llx",
+ recover_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.
+ */
+ local_irq_enable();
+ if (memory_failure(recover_paddr >> PAGE_SHIFT, MCE_VECTOR, flags) < 0) {
+ pr_err("Memory error not recovered");
+ force_sig(SIGBUS, current);
+ }
+ local_irq_disable();
}
EXPORT_SYMBOL_GPL(do_machine_check);
@@ -1185,42 +1159,6 @@ int memory_failure(unsigned long pfn, int vector, int flags)
#endif
/*
- * Called in process context that interrupted by MCE and marked with
- * TIF_MCE_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 mce_notify_process(void)
-{
- unsigned long pfn;
- struct mce_info *mi = mce_find_info();
- int flags = MF_ACTION_REQUIRED;
-
- if (!mi)
- mce_panic("Lost physical address for unconsumed uncorrectable error", NULL, NULL);
- pfn = mi->paddr >> PAGE_SHIFT;
-
- clear_thread_flag(TIF_MCE_NOTIFY);
-
- pr_err("Uncorrected hardware memory error in user-access at %llx",
- mi->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 (!mi->restartable)
- flags |= MF_MUST_KILL;
- if (memory_failure(pfn, MCE_VECTOR, flags) < 0) {
- pr_err("Memory error not recovered");
- force_sig(SIGBUS, current);
- }
- mce_clear_info(mi);
-}
-
-/*
* Action optional processing happens here (picking up
* from the list of faulting pages that do_machine_check()
* placed into the "ring").
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index ed37a768d0fc..2a33c8f68319 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -740,12 +740,6 @@ do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
{
user_exit();
-#ifdef CONFIG_X86_MCE
- /* notify userspace of pending MCEs */
- if (thread_info_flags & _TIF_MCE_NOTIFY)
- mce_notify_process();
-#endif /* CONFIG_X86_64 && CONFIG_X86_MCE */
-
if (thread_info_flags & _TIF_UPROBE)
uprobe_notify_resume(regs);
--
2.1.0
--
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