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9d378dfac8
Previously SPRG3 was marked for use by both VDSO and critical
interrupts (though critical interrupts were not fully implemented).
In commit 8b64a9dfb0 ("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
46 lines
1.3 KiB
ArmAsm
46 lines
1.3 KiB
ArmAsm
/*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* Copyright (C) IBM Corporation, 2012
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*
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* Author: Anton Blanchard <anton@au.ibm.com>
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*/
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#include <asm/ppc_asm.h>
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#include <asm/vdso.h>
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.text
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/*
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* Exact prototype of getcpu
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*
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* int __kernel_getcpu(unsigned *cpu, unsigned *node);
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*
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*/
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V_FUNCTION_BEGIN(__kernel_getcpu)
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.cfi_startproc
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mfspr r5,SPRN_SPRG_VDSO_READ
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cmpdi cr0,r3,0
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cmpdi cr1,r4,0
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clrlwi r6,r5,16
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rlwinm r7,r5,16,31-15,31-0
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beq cr0,1f
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stw r6,0(r3)
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1: beq cr1,2f
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stw r7,0(r4)
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2: crclr cr0*4+so
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li r3,0 /* always success */
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blr
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.cfi_endproc
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V_FUNCTION_END(__kernel_getcpu)
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