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Diffstat (limited to 'arch/powerpc/kernel/signal_64.c')
-rw-r--r--arch/powerpc/kernel/signal_64.c27
1 files changed, 26 insertions, 1 deletions
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 6794466f6420..06c299ef6132 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -565,7 +565,7 @@ static long restore_tm_sigcontexts(struct task_struct *tsk,
preempt_disable();
/* pull in MSR TS bits from user context */
- regs->msr = (regs->msr & ~MSR_TS_MASK) | (msr & MSR_TS_MASK);
+ regs->msr |= msr & MSR_TS_MASK;
/*
* Ensure that TM is enabled in regs->msr before we leave the signal
@@ -745,6 +745,31 @@ SYSCALL_DEFINE0(rt_sigreturn)
if (MSR_TM_SUSPENDED(mfmsr()))
tm_reclaim_current(0);
+ /*
+ * Disable MSR[TS] bit also, so, if there is an exception in the
+ * code below (as a page fault in copy_ckvsx_to_user()), it does
+ * not recheckpoint this task if there was a context switch inside
+ * the exception.
+ *
+ * A major page fault can indirectly call schedule(). A reschedule
+ * process in the middle of an exception can have a side effect
+ * (Changing the CPU MSR[TS] state), since schedule() is called
+ * with the CPU MSR[TS] disable and returns with MSR[TS]=Suspended
+ * (switch_to() calls tm_recheckpoint() for the 'new' process). In
+ * this case, the process continues to be the same in the CPU, but
+ * the CPU state just changed.
+ *
+ * This can cause a TM Bad Thing, since the MSR in the stack will
+ * have the MSR[TS]=0, and this is what will be used to RFID.
+ *
+ * Clearing MSR[TS] state here will avoid a recheckpoint if there
+ * is any process reschedule in kernel space. The MSR[TS] state
+ * does not need to be saved also, since it will be replaced with
+ * the MSR[TS] that came from user context later, at
+ * restore_tm_sigcontexts.
+ */
+ regs->msr &= ~MSR_TS_MASK;
+
if (__get_user(msr, &uc->uc_mcontext.gp_regs[PT_MSR]))
goto badframe;
if (MSR_TM_ACTIVE(msr)) {