From 7f6dc8d4c880f64b9d450d780d88985b264d8793 Mon Sep 17 00:00:00 2001 From: Alexander Gordeev Date: Fri, 18 Jun 2021 08:17:15 +0200 Subject: s390/mcck: always enter C handler with DAT enabled The machine check handler must be entered with DAT disabled in case control registers are corrupted or a storage error happened and we can not tell if such error corresponds to a page table. Both of described conditions end up in stopping all CPUs and entering the disabled wait in C half of the handler. However, the storage errors are still checked after the DAT is enabled and C code is entered. In case a page table is damaged such flow is not expected to work. This update paves the way for moving the storage error checks from C to assembler half. All fatal errors that can only be handled with DAT disabled are handled in assembler half also. As result, the C half is only entered if the DAT is secured. Signed-off-by: Alexander Gordeev Reviewed-by: Heiko Carstens Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik --- arch/s390/kernel/entry.S | 35 ++++++++++++++++++++++++++++++++--- arch/s390/kernel/nmi.c | 29 ----------------------------- 2 files changed, 32 insertions(+), 32 deletions(-) diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S index ff715cc2b77b..6bc8ed800458 100644 --- a/arch/s390/kernel/entry.S +++ b/arch/s390/kernel/entry.S @@ -570,7 +570,6 @@ ENTRY(mcck_int_handler) BPENTER __TI_flags(%r12),_TIF_ISOLATE_BP .Lmcck_stack: lg %r15,__LC_MCCK_STACK -.Lmcck_skip: la %r11,STACK_FRAME_OVERHEAD(%r15) stctg %c1,%c1,__PT_CR1(%r11) lctlg %c1,%c1,__LC_KERNEL_ASCE @@ -612,8 +611,33 @@ ENTRY(mcck_int_handler) b __LC_RETURN_MCCK_LPSWE .Lmcck_panic: - lg %r15,__LC_NODAT_STACK - j .Lmcck_skip + /* + * Iterate over all possible CPU addresses in the range 0..0xffff + * and stop each CPU using signal processor. Use compare and swap + * to allow just one CPU-stopper and prevent concurrent CPUs from + * stopping each other while leaving the others running. + */ + lhi %r5,0 + lhi %r6,1 + larl %r7,.Lstop_lock + cs %r5,%r6,0(%r7) # single CPU-stopper only + jnz 4f + larl %r7,.Lthis_cpu + stap 0(%r7) # this CPU address + lh %r4,0(%r7) + nilh %r4,0 + lhi %r0,1 + sll %r0,16 # CPU counter + lhi %r3,0 # next CPU address +0: cr %r3,%r4 + je 2f +1: sigp %r1,%r3,SIGP_STOP # stop next CPU + brc SIGP_CC_BUSY,1b +2: ahi %r3,1 + brct %r0,0b +3: sigp %r1,%r4,SIGP_STOP # stop this CPU + brc SIGP_CC_BUSY,3b +4: j 4b ENDPROC(mcck_int_handler) # @@ -664,6 +688,11 @@ ENTRY(stack_overflow) ENDPROC(stack_overflow) #endif + .section .data, "aw" + .align 4 +.Lstop_lock: .long 0 +.Lthis_cpu: .short 0 + .section .rodata, "a" #define SYSCALL(esame,emu) .quad __s390x_ ## esame .globl sys_call_table diff --git a/arch/s390/kernel/nmi.c b/arch/s390/kernel/nmi.c index 11f8c296f60d..a424f6e69b95 100644 --- a/arch/s390/kernel/nmi.c +++ b/arch/s390/kernel/nmi.c @@ -205,14 +205,6 @@ static int notrace s390_check_registers(union mci mci, int umode) s390_handle_damage(); kill_task = 1; } - /* Check control registers */ - if (!mci.cr) { - /* - * Control registers have unknown contents. - * Can't recover and therefore stopping machine. - */ - s390_handle_damage(); - } if (!mci.fp) { /* * Floating point registers can't be restored. If the @@ -273,22 +265,6 @@ static int notrace s390_check_registers(union mci mci, int umode) kill_task = 1; } } - /* Check if old PSW is valid */ - if (!mci.wp) { - /* - * Can't tell if we come from user or kernel mode - * -> stopping machine. - */ - s390_handle_damage(); - } - /* Check for invalid kernel instruction address */ - if (!mci.ia && !umode) { - /* - * The instruction address got lost while running - * in the kernel -> stopping machine. - */ - s390_handle_damage(); - } if (!mci.ms || !mci.pm || !mci.ia) kill_task = 1; @@ -353,11 +329,6 @@ int notrace s390_do_machine_check(struct pt_regs *regs) mci.val = S390_lowcore.mcck_interruption_code; mcck = this_cpu_ptr(&cpu_mcck); - if (mci.sd) { - /* System damage -> stopping machine */ - s390_handle_damage(); - } - /* * Reinject the instruction processing damages' machine checks * including Delayed Access Exception into the guest -- cgit v1.2.3