linux-stable.git/arch/s390/include/asm/processor.h, branch linux-4.4.y

s390: run user space and KVM guests with modified branch prediction

2018-04-29T05:50:03+00:00

[ Upstream commit 6b73044b2b0081ee3dd1cd6eaab7dee552601efb ]

Define TIF_ISOLATE_BP and TIF_ISOLATE_BP_GUEST and add the necessary
plumbing in entry.S to be able to run user space and KVM guests with
limited branch prediction.

To switch a user space process to limited branch prediction the
s390_isolate_bp() function has to be call, and to run a vCPU of a KVM
guest associated with the current task with limited branch prediction
call s390_isolate_bp_guest().

Signed-off-by: Martin Schwidefsky 
Signed-off-by: Greg Kroah-Hartman

s390: add options to change branch prediction behaviour for the kernel

2018-04-29T05:50:03+00:00

[ Upstream commit d768bd892fc8f066cd3aa000eb1867bcf32db0ee ]

Add the PPA instruction to the system entry and exit path to switch
the kernel to a different branch prediction behaviour. The instructions
are added via CPU alternatives and can be disabled with the "nospec"
or the "nobp=0" kernel parameter. If the default behaviour selected
with CONFIG_KERNEL_NOBP is set to "n" then the "nobp=1" parameter can be
used to enable the changed kernel branch prediction.

Acked-by: Cornelia Huck 
Signed-off-by: Martin Schwidefsky 
Signed-off-by: Greg Kroah-Hartman

s390: TASK_SIZE for kernel threads

2017-03-15T01:57:12+00:00

commit fb94a687d96c570d46332a4a890f1dcb7310e643 upstream.

Return a sensible value if TASK_SIZE if called from a kernel thread.

This gets us around an issue with copy_mount_options that does a magic
size calculation "TASK_SIZE - (unsigned long)data" while in a kernel
thread and data pointing to kernel space.

Signed-off-by: Martin Schwidefsky 
Signed-off-by: Greg Kroah-Hartman

s390/mm: fix asce_bits handling with dynamic pagetable levels

2016-05-19T00:06:44+00:00

commit 723cacbd9dc79582e562c123a0bacf8bfc69e72a upstream.

There is a race with multi-threaded applications between context switch and
pagetable upgrade. In switch_mm() a new user_asce is built from mm->pgd and
mm->context.asce_bits, w/o holding any locks. A concurrent mmap with a
pagetable upgrade on another thread in crst_table_upgrade() could already
have set new asce_bits, but not yet the new mm->pgd. This would result in a
corrupt user_asce in switch_mm(), and eventually in a kernel panic from a
translation exception.

Fix this by storing the complete asce instead of just the asce_bits, which
can then be read atomically from switch_mm(), so that it either sees the
old value or the new value, but no mixture. Both cases are OK. Having the
old value would result in a page fault on access to the higher level memory,
but the fault handler would see the new mm->pgd, if it was a valid access
after the mmap on the other thread has completed. So as worst-case scenario
we would have a page fault loop for the racing thread until the next time
slice.

Also remove dead code and simplify the upgrade/downgrade path, there are no
upgrades from 2 levels, and only downgrades from 3 levels for compat tasks.
There are also no concurrent upgrades, because the mmap_sem is held with
down_write() in do_mmap, so the flush and table checks during upgrade can
be removed.

Reported-by: Michael Munday 
Reviewed-by: Martin Schwidefsky 
Signed-off-by: Gerald Schaefer 
Signed-off-by: Martin Schwidefsky 
Signed-off-by: Greg Kroah-Hartman

s390: remove runtime instrumentation interrupts

2015-11-03T13:40:51+00:00

The external interrupts for runtime instrumentation buffer-full
and runtime instrumentation halted are unused and have no current
user. Remove the support and ignore the second parameter of the
s390_runtime_instr system call from now on.

Signed-off-by: Martin Schwidefsky

s390: don't store registers on disabled wait anymore

2015-10-27T08:33:48+00:00

The current disabled wait code stores register contents into their
save areas, however it is (at least) missing the new vector registers.

Given the fact that the whole exercise seems to be rather pointless
simply don't save any registers anymore.

In a "live" system it is always possible to inspect register contents,
and in case of a dump the register contents will be stored by the
dump mechanism.

Signed-off-by: Heiko Carstens 
Signed-off-by: Martin Schwidefsky

s390: get rid of __set_psw_mask()

2015-10-27T08:33:44+00:00

With the removal of 31 bit code we can always assume that the epsw
instruction is available. Therefore use the __extract_psw() function
to disable and enable machine checks.

Signed-off-by: Heiko Carstens 
Signed-off-by: Martin Schwidefsky

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

2015-10-16T07:41:12+00:00

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/flags: use _BITUL macro

2015-10-14T12:32:14+00:00

The defines that are used in entry.S have been partially converted to
use the _BITUL macro (setup.h). This patch converts the rest.

Signed-off-by: Heiko Carstens 
Reviewed-by: Hendrik Brueckner 
Signed-off-by: Martin Schwidefsky

s390/flags: fix flag handling

2015-10-14T12:32:14+00:00

The cpu flags and pt_regs flags fields are each 64 bits in size. A flag can
be set with helper functions like set_cpu_flags().

These functions create a mask using "1U << flag". This doesn't work if flag
is larger than 31, since 1U << 32 == 0.

So fix this in case we ever will have such flag numbers.

Signed-off-by: Heiko Carstens 
Reviewed-by: Hendrik Brueckner 
Signed-off-by: Martin Schwidefsky