From: Martin Schwidefsky Date: Fri, 27 Apr 2018 05:36:36 +0000 (+0200) Subject: s390: do not bypass BPENTER for interrupt system calls X-Git-Tag: v4.14.38~28 X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=74a93ae5c328da09951990e1fece3382b544616c;p=users%2Fdwmw2%2Flinux.git s390: do not bypass BPENTER for interrupt system calls [ Upstream commit d5feec04fe578c8dbd9e2e1439afc2f0af761ed4 ] The system call path can be interrupted before the switch back to the standard branch prediction with BPENTER has been done. The critical section cleanup code skips forward to .Lsysc_do_svc and bypasses the BPENTER. In this case the kernel and all subsequent code will run with the limited branch prediction. Fixes: eacf67eb9b32 ("s390: run user space and KVM guests with modified branch prediction") Signed-off-by: Martin Schwidefsky Signed-off-by: Greg Kroah-Hartman --- diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S index 1888b1010e20a..6473cd81c8f6f 100644 --- a/arch/s390/kernel/entry.S +++ b/arch/s390/kernel/entry.S @@ -1375,6 +1375,7 @@ cleanup_critical: stg %r15,__LC_SYSTEM_TIMER 0: # update accounting time stamp mvc __LC_LAST_UPDATE_TIMER(8),__LC_SYNC_ENTER_TIMER + BPENTER __TI_flags(%r12),_TIF_ISOLATE_BP # set up saved register r11 lg %r15,__LC_KERNEL_STACK la %r9,STACK_FRAME_OVERHEAD(%r15)