linux.git/arch/powerpc/kernel/process.c, branch v4.6-rc2

powerpc/process: Fix altivec SPR not being saved

2016-03-29T01:08:08+00:00

In save_sprs() in process.c contains the following test:

	if (cpu_has_feature(cpu_has_feature(CPU_FTR_ALTIVEC)))
		t->vrsave = mfspr(SPRN_VRSAVE);

CPU feature with the mask 0x1 is CPU_FTR_COHERENT_ICACHE so the test
is equivilent to:

	if (cpu_has_feature(CPU_FTR_ALTIVEC) &&
		cpu_has_feature(CPU_FTR_COHERENT_ICACHE))

On CPUs without support for both (i.e G5) this results in vrsave not
being saved between context switches. The vector register save/restore
code doesn't use VRSAVE to determine which registers to save/restore,
but the value of VRSAVE is used to determine if altivec is being used
in several code paths.

Fixes: 152d523e6307 ("powerpc: Create context switch helpers save_sprs() and restore_sprs()")
Cc: stable@vger.kernel.org
Signed-off-by: Oliver O'Halloran 
Signed-off-by: Anton Blanchard 
Signed-off-by: Michael Ellerman

Merge tag 'powerpc-4.6-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

2016-03-19T22:38:41+00:00

Pull powerpc updates from Michael Ellerman:
 "This was delayed a day or two by some build-breakage on old toolchains
  which we've now fixed.

  There's two PCI commits both acked by Bjorn.

  There's one commit to mm/hugepage.c which is (co)authored by Kirill.

  Highlights:
   - Restructure Linux PTE on Book3S/64 to Radix format from Paul
     Mackerras
   - Book3s 64 MMU cleanup in preparation for Radix MMU from Aneesh
     Kumar K.V
   - Add POWER9 cputable entry from Michael Neuling
   - FPU/Altivec/VSX save/restore optimisations from Cyril Bur
   - Add support for new ftrace ABI on ppc64le from Torsten Duwe

  Various cleanups & minor fixes from:
   - Adam Buchbinder, Andrew Donnellan, Balbir Singh, Christophe Leroy,
     Cyril Bur, Luis Henriques, Madhavan Srinivasan, Pan Xinhui, Russell
     Currey, Sukadev Bhattiprolu, Suraj Jitindar Singh.

  General:
   - atomics: Allow architectures to define their own __atomic_op_*
     helpers from Boqun Feng
   - Implement atomic{, 64}_*_return_* variants and acquire/release/
     relaxed variants for (cmp)xchg from Boqun Feng
   - Add powernv_defconfig from Jeremy Kerr
   - Fix BUG_ON() reporting in real mode from Balbir Singh
   - Add xmon command to dump OPAL msglog from Andrew Donnellan
   - Add xmon command to dump process/task similar to ps(1) from Douglas
     Miller
   - Clean up memory hotplug failure paths from David Gibson

  pci/eeh:
   - Redesign SR-IOV on PowerNV to give absolute isolation between VFs
     from Wei Yang.
   - EEH Support for SRIOV VFs from Wei Yang and Gavin Shan.
   - PCI/IOV: Rename and export virtfn_{add, remove} from Wei Yang
   - PCI: Add pcibios_bus_add_device() weak function from Wei Yang
   - MAINTAINERS: Update EEH details and maintainership from Russell
     Currey

  cxl:
   - Support added to the CXL driver for running on both bare-metal and
     hypervisor systems, from Christophe Lombard and Frederic Barrat.
   - Ignore probes for virtual afu pci devices from Vaibhav Jain

  perf:
   - Export Power8 generic and cache events to sysfs from Sukadev
     Bhattiprolu
   - hv-24x7: Fix usage with chip events, display change in counter
     values, display domain indices in sysfs, eliminate domain suffix in
     event names, from Sukadev Bhattiprolu

  Freescale:
   - Updates from Scott: "Highlights include 8xx optimizations, 32-bit
     checksum optimizations, 86xx consolidation, e5500/e6500 cpu
     hotplug, more fman and other dt bits, and minor fixes/cleanup"

* tag 'powerpc-4.6-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: (179 commits)
  powerpc: Fix unrecoverable SLB miss during restore_math()
  powerpc/8xx: Fix do_mtspr_cpu6() build on older compilers
  powerpc/rcpm: Fix build break when SMP=n
  powerpc/book3e-64: Use hardcoded mttmr opcode
  powerpc/fsl/dts: Add "jedec,spi-nor" flash compatible
  powerpc/T104xRDB: add tdm riser card node to device tree
  powerpc32: PAGE_EXEC required for inittext
  powerpc/mpc85xx: Add pcsphy nodes to FManV3 device tree
  powerpc/mpc85xx: Add MDIO bus muxing support to the board device tree(s)
  powerpc/86xx: Introduce and use common dtsi
  powerpc/86xx: Update device tree
  powerpc/86xx: Move dts files to fsl directory
  powerpc/86xx: Switch to kconfig fragments approach
  powerpc/86xx: Update defconfigs
  powerpc/86xx: Consolidate common platform code
  powerpc32: Remove one insn in mulhdu
  powerpc32: small optimisation in flush_icache_range()
  powerpc: Simplify test in __dma_sync()
  powerpc32: move xxxxx_dcache_range() functions inline
  powerpc32: Remove clear_pages() and define clear_page() inline
  ...

powerpc: Add the ability to save VSX without giving it up

2016-03-02T12:34:50+00:00

This patch adds the ability to be able to save the VSX registers to the
thread struct without giving up (disabling the facility) next time the
process returns to userspace.

This patch builds on a previous optimisation for the FPU and VEC registers
in the thread copy path to avoid a possibly pointless reload of VSX state.

Signed-off-by: Cyril Bur 
Signed-off-by: Michael Ellerman

powerpc: Add the ability to save Altivec without giving it up

2016-03-02T12:34:49+00:00

This patch adds the ability to be able to save the VEC registers to the
thread struct without giving up (disabling the facility) next time the
process returns to userspace.

This patch builds on a previous optimisation for the FPU registers in the
thread copy path to avoid a possibly pointless reload of VEC state.

Signed-off-by: Cyril Bur 
Signed-off-by: Michael Ellerman

powerpc: Add the ability to save FPU without giving it up

2016-03-02T12:34:49+00:00

This patch adds the ability to be able to save the FPU registers to the
thread struct without giving up (disabling the facility) next time the
process returns to userspace.

This patch optimises the thread copy path (as a result of a fork() or
clone()) so that the parent thread can return to userspace with hot
registers avoiding a possibly pointless reload of FPU register state.

Signed-off-by: Cyril Bur 
Signed-off-by: Michael Ellerman

powerpc: Prepare for splitting giveup_{fpu, altivec, vsx} in two

2016-03-02T12:34:48+00:00

This prepares for the decoupling of saving {fpu,altivec,vsx} registers and
marking {fpu,altivec,vsx} as being unused by a thread.

Currently giveup_{fpu,altivec,vsx}() does both however optimisations to
task switching can be made if these two operations are decoupled.
save_all() will permit the saving of registers to thread structs and leave
threads MSR with bits enabled.

This patch introduces no functional change.

Signed-off-by: Cyril Bur 
Signed-off-by: Michael Ellerman

powerpc: Restore FPU/VEC/VSX if previously used

2016-03-02T12:34:48+00:00

Currently the FPU, VEC and VSX facilities are lazily loaded. This is not
a problem unless a process is using these facilities.

Modern versions of GCC are very good at automatically vectorising code,
new and modernised workloads make use of floating point and vector
facilities, even the kernel makes use of vectorised memcpy.

All this combined greatly increases the cost of a syscall since the
kernel uses the facilities sometimes even in syscall fast-path making it
increasingly common for a thread to take an *_unavailable exception soon
after a syscall, not to mention potentially taking all three.

The obvious overcompensation to this problem is to simply always load
all the facilities on every exit to userspace. Loading up all FPU, VEC
and VSX registers every time can be expensive and if a workload does
avoid using them, it should not be forced to incur this penalty.

An 8bit counter is used to detect if the registers have been used in the
past and the registers are always loaded until the value wraps to back
to zero.

Several versions of the assembly in entry_64.S were tested:

  1. Always calling C.
  2. Performing a common case check and then calling C.
  3. A complex check in asm.

After some benchmarking it was determined that avoiding C in the common
case is a performance benefit (option 2). The full check in asm (option
3) greatly complicated that codepath for a negligible performance gain
and the trade-off was deemed not worth it.

Signed-off-by: Cyril Bur 
[mpe: Move load_vec in the struct to fill an existing hole, reword change log]
Signed-off-by: Michael Ellerman 

fixup

powerpc: Explicitly disable math features when copying thread

2016-03-02T12:34:47+00:00

Currently when threads get scheduled off they always giveup the FPU,
Altivec (VMX) and Vector (VSX) units if they were using them. When they are
scheduled back on a fault is then taken to enable each facility and load
registers. As a result explicitly disabling FPU/VMX/VSX has not been
necessary.

Future changes and optimisations remove this mandatory giveup and fault
which could cause calls such as clone() and fork() to copy threads and run
them later with FPU/VMX/VSX enabled but no registers loaded.

This patch starts the process of having MSR_{FP,VEC,VSX} mean that a
threads registers are hot while not having MSR_{FP,VEC,VSX} means that the
registers must be loaded. This allows for a smarter return to userspace.

Signed-off-by: Cyril Bur 
Signed-off-by: Michael Ellerman

mm: ASLR: use get_random_long()

2016-02-27T18:28:52+00:00

Replace calls to get_random_int() followed by a cast to (unsigned long)
with calls to get_random_long().  Also address shifting bug which, in
case of x86 removed entropy mask for mmap_rnd_bits values > 31 bits.

Signed-off-by: Daniel Cashman 
Acked-by: Kees Cook 
Cc: "Theodore Ts'o" 
Cc: Arnd Bergmann 
Cc: Greg Kroah-Hartman 
Cc: Catalin Marinas 
Cc: Will Deacon 
Cc: Ralf Baechle 
Cc: Benjamin Herrenschmidt 
Cc: Paul Mackerras 
Cc: Michael Ellerman 
Cc: David S. Miller 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: H. Peter Anvin 
Cc: Al Viro 
Cc: Nick Kralevich 
Cc: Jeff Vander Stoep 
Cc: Mark Salyzyn 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge tag 'powerpc-4.4-3' into next

2015-12-14T09:40:32+00:00

Merge the two TM fixes we merged in 4.4. We are about to merge selftests
for these, and without the fixes the selftests will oops.

powerpc fixes for 4.4 #2

 - tm: Block signal return from setting invalid MSR state from Michael Neuling
 - tm: Check for already reclaimed tasks from Michael Neuling