kernel.git/arch/s390/kernel/nmi.c, branch linux-4.6.y

s390/nmi: reduce size of percpu variable

2015-10-27T08:33:57Z

Change the flag fields within struct mcck_struct to simple bit fields to reduce the size of the structure which is used as percpu variable. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/nmi: fix terminology

2015-10-27T08:33:56Z

According to the architecture registers are validated and not revalidated. So change comments and functions names to match. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/nmi: remove casts

2015-10-27T08:33:55Z

Remove all the casts to and from the machine check interruption code. This patch changes struct mci to a union, which contains an anonymous structure with the already known bits and in addition an unsigned long field, which contains the raw machine check interruption code. This allows to simply assign and decoce the interruption code value without the need for all those casts we had all the time. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/nmi: remove pointless error strings

2015-10-27T08:33:54Z

s390_handle_damage() has character string parameter which was used as a pointer to verbose error message. The hope was (a lot of years ago) when analyzing dumps that register R2 would still contain the pointer and therefore it would be rather easy to tell what went wrong. However gcc optimizes the strings away since a long time. And even if it wouldn't it is necessary to have a close look at the machine check interruption code to tell what's wrong. So remove the pointless error strings. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/fpu: split fpu-internal.h into fpu internals, api, and type headers

2015-10-16T07:41:12Z

Split the API and FPU type definitions into separate header files similar to "x86/fpu: Rename fpu-internal.h to fpu/internal.h" (78f7f1e54b). The new header files and their meaning are: asm/fpu/types.h: FPU related data types, needed for 'struct thread_struct' and 'struct task_struct'. asm/fpu/api.h: FPU related 'public' functions for other subsystems and device drivers. asm/fpu/internal.h: FPU internal functions mainly used to convert FPU register contents in signal handling. Signed-off-by: Hendrik Brueckner Signed-off-by: Martin Schwidefsky

s390/etr,stp: fix possible deadlock on machine check

2015-10-14T12:32:18Z

The first level machine check handler for etr and stp machine checks may call queue_work() while in nmi context. This may deadlock e.g. if the machine check happened when the interrupted context did hold a lock, that also will be acquired by queue_work(). Therefore split etr and stp machine check handling into first and second level handling. The second level handling will then issue the queue_work() call in process context which avoids the potential deadlock. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/nmi: initialize control register 0 earlier

2015-08-19T08:40:38Z

Change machine_check_init() to an early_initcall(). This makes sure it will be called before all other cpus are online and therfore saves us a lot of pointless smp_call_function() calls. The control register settings will be forwarded to the other cpus when they will be brought online. Signed-off-by: Heiko Carstens Reviewed-by: Hendrik Brueckner Signed-off-by: Martin Schwidefsky

s390/kernel: lazy restore fpu registers

2015-07-22T07:58:01Z

Improve the save and restore behavior of FPU register contents to use the vector extension within the kernel. The kernel does not use floating-point or vector registers and, therefore, saving and restoring the FPU register contents are performed for handling signals or switching processes only. To prepare for using vector instructions and vector registers within the kernel, enhance the save behavior and implement a lazy restore at return to user space from a system call or interrupt. To implement the lazy restore, the save_fpu_regs() sets a CPU information flag, CIF_FPU, to indicate that the FPU registers must be restored. Saving and setting CIF_FPU is performed in an atomic fashion to be interrupt-safe. When the kernel wants to use the vector extension or wants to change the FPU register state for a task during signal handling, the save_fpu_regs() must be called first. The CIF_FPU flag is also set at process switch. At return to user space, the FPU state is restored. In particular, the FPU state includes the floating-point or vector register contents, as well as, vector-enablement and floating-point control. The FPU state restore and clearing CIF_FPU is also performed in an atomic fashion. For KVM, the restore of the FPU register state is performed when restoring the general-purpose guest registers before the SIE instructions is started. Because the path towards the SIE instruction is interruptible, the CIF_FPU flag must be checked again right before going into SIE. If set, the guest registers must be reloaded again by re-entering the outer SIE loop. This is the same behavior as if the SIE critical section is interrupted. Signed-off-by: Hendrik Brueckner Signed-off-by: Martin Schwidefsky

s390/kernel: introduce fpu-internal.h with fpu helper functions

2015-07-22T07:58:00Z

Introduce a new structure to manage FP and VX registers. Refactor the save and restore of floating point and vector registers with a set of helper functions in fpu-internal.h. Signed-off-by: Hendrik Brueckner Signed-off-by: Martin Schwidefsky

s390/nmi: fix vector register corruption

2015-07-13T09:02:21Z

If a machine check happens, the machine has the vector facility installed and the extended save area exists, the cpu will save vector register contents into the extended save area. This is regardless of control register 0 contents, which enables and disables the vector facility during runtime. On each machine check we should validate the vector registers. The current code however tries to validate the registers only if the running task is using vector registers in user space. However even the current code is broken and causes vector register corruption on machine checks, if user space uses them: the prefix area contains a pointer (absolute address) to the machine check extended save area. In order to save some space the save area was put into an unused area of the second prefix page. When validating vector register contents the code uses the absolute address of the extended save area, which is wrong. Due to prefixing the vector instructions will then access contents using absolute addresses instead of real addresses, where the machine stored the contents. If the above would work there is still the problem that register validition would only happen if user space uses vector registers. If kernel space uses them also, this may also lead to vector register content corruption: if the kernel makes use of vector instructions, but the current running user space context does not, the machine check handler will validate floating point registers instead of vector registers. Given the fact that writing to a floating point register may change the upper halve of the corresponding vector register, we also experience vector register corruption in this case. Fix all of these issues, and always validate vector registers on each machine check, if the machine has the vector facility installed and the extended save area is defined. Cc: # 4.1+ Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky