diff options
| author | Michael Neuling <mikey@neuling.org> | 2013-08-09 09:29:29 +0200 |
|---|---|---|
| committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2013-08-09 10:07:05 +0200 |
| commit | 2517617e0de65f8f7cfe75cae745d06b1fa98586 (patch) | |
| tree | e0350aa1f8260dc0b25ab7adf3b83d7ab0b46060 /arch/powerpc/kernel/entry_64.S | |
| parent | powerpc: Rework setting up H/FSCR bit definitions (diff) | |
| download | linux-2517617e0de65f8f7cfe75cae745d06b1fa98586.tar.xz linux-2517617e0de65f8f7cfe75cae745d06b1fa98586.zip | |
powerpc: Fix context switch DSCR on POWER8
POWER8 allows the DSCR to be accessed directly from userspace via a new SPR
number 0x3 (Rather than 0x11. DSCR SPR number 0x11 is still used on POWER8 but
like POWER7, is only accessible in HV and OS modes). Currently, we allow this
by setting H/FSCR DSCR bit on boot.
Unfortunately this doesn't work, as the kernel needs to see the DSCR change so
that it knows to no longer restore the system wide version of DSCR on context
switch (ie. to set thread.dscr_inherit).
This clears the H/FSCR DSCR bit initially. If a process then accesses the DSCR
(via SPR 0x3), it'll trap into the kernel where we set thread.dscr_inherit in
facility_unavailable_exception().
We also change _switch() so that we set or clear the H/FSCR DSCR bit based on
the thread.dscr_inherit.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Cc: <stable@vger.kernel.org> [v3.10]
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/kernel/entry_64.S')
| -rw-r--r-- | arch/powerpc/kernel/entry_64.S | 27 |
1 files changed, 26 insertions, 1 deletions
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index ab15b8d057ad..4674fe647ad7 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -584,9 +584,34 @@ BEGIN_FTR_SECTION ld r7,DSCR_DEFAULT@toc(2) ld r0,THREAD_DSCR(r4) cmpwi r6,0 + li r8, FSCR_DSCR bne 1f ld r0,0(r7) -1: cmpd r0,r25 + b 3f +1: + BEGIN_FTR_SECTION_NESTED(70) + mfspr r6, SPRN_FSCR + or r6, r6, r8 + mtspr SPRN_FSCR, r6 + BEGIN_FTR_SECTION_NESTED(69) + mfspr r6, SPRN_HFSCR + or r6, r6, r8 + mtspr SPRN_HFSCR, r6 + END_FTR_SECTION_NESTED(CPU_FTR_HVMODE, CPU_FTR_HVMODE, 69) + b 4f + END_FTR_SECTION_NESTED(CPU_FTR_ARCH_207S, CPU_FTR_ARCH_207S, 70) +3: + BEGIN_FTR_SECTION_NESTED(70) + mfspr r6, SPRN_FSCR + andc r6, r6, r8 + mtspr SPRN_FSCR, r6 + BEGIN_FTR_SECTION_NESTED(69) + mfspr r6, SPRN_HFSCR + andc r6, r6, r8 + mtspr SPRN_HFSCR, r6 + END_FTR_SECTION_NESTED(CPU_FTR_HVMODE, CPU_FTR_HVMODE, 69) + END_FTR_SECTION_NESTED(CPU_FTR_ARCH_207S, CPU_FTR_ARCH_207S, 70) +4: cmpd r0,r25 beq 2f mtspr SPRN_DSCR,r0 2: |