Commit-ID: 3ae6295ccb7cf6d344908209701badbbbb503e40 Gitweb: https://git.kernel.org/tip/3ae6295ccb7cf6d344908209701badbbbb503e40 Author: Siarhei Liakh <[email protected]> AuthorDate: Thu, 14 Jun 2018 19:36:07 +0000 Committer: Thomas Gleixner <[email protected]> CommitDate: Wed, 20 Jun 2018 11:44:56 +0200
x86: Call fixup_exception() before notify_die() in math_error() 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 <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Reviewed-by: Andy Lutomirski <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: "Borislav Petkov" <[email protected]> Cc: [email protected] Link: https://lkml.kernel.org/r/dm5pr11mb201156f1cab2592b07c79a03b1...@dm5pr11mb2011.namprd11.prod.outlook.com --- arch/x86/kernel/traps.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 03f3d7695dac..162a31d80ad5 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -834,16 +834,18 @@ static void math_error(struct pt_regs *regs, int error_code, int trapnr) 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; }
