From 915fea04f9320d0f4ab6ecbb6bf759eebcd2c41d Mon Sep 17 00:00:00 2001 From: Alexander Gordeev Date: Tue, 24 Aug 2021 15:30:21 +0200 Subject: s390/smp: enable DAT before CPU restart callback is called The restart interrupt is triggered whenever a secondary CPU is brought online, a remote function call dispatched from another CPU or a manual PSW restart is initiated and causes the system to kdump. The handling routine is always called with DAT turned off. It then initializes the stack frame and invokes a callback. The existing callbacks handle DAT as follows: * __do_restart() and __machine_kexec() turn in on upon entry; * __ipl_run(), __reipl_run() and __dump_run() do not turn it right away, but all of them call diag308() - which turns DAT on, but only if kasan is enabled; In addition to the described complexity all callbacks (and the functions they call) should avoid kasan instrumentation while DAT is off. This update enables DAT in the assembler restart handler and relieves any callbacks (which are mostly C functions) from dealing with DAT altogether. There are four types of CPU restart that initialize control registers in different ways: 1. Start of secondary CPU on boot - control registers are inherited from the IPL CPU; 2. Restart of online CPU - control registers of the CPU being restarted are kept; 3. Hotplug of offline CPU - control registers are inherited from the starting CPU; 4. Start of offline CPU triggered by manual PSW restart - the control registers are read from the absolute lowcore and contain the boot time IPL CPU values updated with all follow-up calls of smp_ctl_set_bit() and smp_ctl_clear_bit() routines; In first three cases contents of the control registers is the most recent. In the latter case control registers are good enough to facilitate successful completion of kdump operation. Suggested-by: Heiko Carstens Signed-off-by: Alexander Gordeev Signed-off-by: Heiko Carstens --- arch/s390/include/asm/processor.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'arch/s390/include/asm/processor.h') diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h index ddc7858bbce4..879b8e3f609c 100644 --- a/arch/s390/include/asm/processor.h +++ b/arch/s390/include/asm/processor.h @@ -26,6 +26,8 @@ #define _CIF_MCCK_GUEST BIT(CIF_MCCK_GUEST) #define _CIF_DEDICATED_CPU BIT(CIF_DEDICATED_CPU) +#define RESTART_FLAG_CTLREGS _AC(1 << 0, U) + #ifndef __ASSEMBLY__ #include -- cgit v1.2.3