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authorScott Wood <scottwood@freescale.com>2014-03-10 17:29:38 -0500
committerScott Wood <scottwood@freescale.com>2014-03-19 19:57:14 -0500
commit9d378dfac885f72b8b369d08fc61bef36e2f2dd1 (patch)
tree8790aa68cd0944e031b35eb63f5be14ec678be2d /arch/powerpc/kernel/vdso64
parent82d86de25b9c99db546e17c6f7ebf9a691da557e (diff)
powerpc/booke64: Use SPRG7 for VDSO
Previously SPRG3 was marked for use by both VDSO and critical interrupts (though critical interrupts were not fully implemented). In commit 8b64a9dfb091f1eca8b7e58da82f1e7d1d5fe0ad ("powerpc/booke64: Use SPRG0/3 scratch for bolted TLB miss & crit int"), Mihai Caraman made an attempt to resolve this conflict by restoring the VDSO value early in the critical interrupt, but this has some issues: - It's incompatible with EXCEPTION_COMMON which restores r13 from the by-then-overwritten scratch (this cost me some debugging time). - It forces critical exceptions to be a special case handled differently from even machine check and debug level exceptions. - It didn't occur to me that it was possible to make this work at all (by doing a final "ld r13, PACA_EXCRIT+EX_R13(r13)") until after I made (most of) this patch. :-) It might be worth investigating using a load rather than SPRG on return from all exceptions (except TLB misses where the scratch never leaves the SPRG) -- it could save a few cycles. Until then, let's stick with SPRG for all exceptions. Since we cannot use SPRG4-7 for scratch without corrupting the state of a KVM guest, move VDSO to SPRG7 on book3e. Since neither SPRG4-7 nor critical interrupts exist on book3s, SPRG3 is still used for VDSO there. Signed-off-by: Scott Wood <scottwood@freescale.com> Cc: Mihai Caraman <mihai.caraman@freescale.com> Cc: Anton Blanchard <anton@samba.org> Cc: Paul Mackerras <paulus@samba.org> Cc: kvm-ppc@vger.kernel.org
Diffstat (limited to 'arch/powerpc/kernel/vdso64')
-rw-r--r--arch/powerpc/kernel/vdso64/getcpu.S2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/powerpc/kernel/vdso64/getcpu.S b/arch/powerpc/kernel/vdso64/getcpu.S
index 47afd08c90f7..23eb9a9441bd 100644
--- a/arch/powerpc/kernel/vdso64/getcpu.S
+++ b/arch/powerpc/kernel/vdso64/getcpu.S
@@ -29,7 +29,7 @@
*/
V_FUNCTION_BEGIN(__kernel_getcpu)
.cfi_startproc
- mfspr r5,SPRN_USPRG3
+ mfspr r5,SPRN_SPRG_VDSO_READ
cmpdi cr0,r3,0
cmpdi cr1,r4,0
clrlwi r6,r5,16