4.9-stable review patch. If anyone has any objections, please let me know.
------------------ From: Siarhei Liakh <siarhei.li...@concurrent-rt.com> commit 3ae6295ccb7cf6d344908209701badbbbb503e40 upstream. fpu__drop() has an explicit fwait which under some conditions can trigger a fixable FPU exception while in kernel. Thus, we should attempt to fixup the exception first, and only call notify_die() if the fixup failed just like in do_general_protection(). The original call sequence incorrectly triggers KDB entry on debug kernels under particular FPU-intensive workloads. Andy noted, that this makes the whole conditional irq enable thing even more inconsistent, but fixing that it outside the scope of this. Signed-off-by: Siarhei Liakh <siarhei.li...@concurrent-rt.com> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Reviewed-by: Andy Lutomirski <l...@kernel.org> Cc: "H. Peter Anvin" <h...@zytor.com> Cc: "Borislav Petkov" <bpet...@suse.de> Cc: sta...@vger.kernel.org Link: https://lkml.kernel.org/r/dm5pr11mb201156f1cab2592b07c79a03b1...@dm5pr11mb2011.namprd11.prod.outlook.com Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- arch/x86/kernel/traps.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -799,16 +799,18 @@ static void math_error(struct pt_regs *r char *str = (trapnr == X86_TRAP_MF) ? "fpu exception" : "simd exception"; - if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, SIGFPE) == NOTIFY_STOP) - return; cond_local_irq_enable(regs); if (!user_mode(regs)) { - if (!fixup_exception(regs, trapnr)) { - task->thread.error_code = error_code; - task->thread.trap_nr = trapnr; + if (fixup_exception(regs, trapnr)) + return; + + task->thread.error_code = error_code; + task->thread.trap_nr = trapnr; + + if (notify_die(DIE_TRAP, str, regs, error_code, + trapnr, SIGFPE) != NOTIFY_STOP) die(str, regs, error_code); - } return; }
