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powerpc: Provide for giveup_fpu/altivec to save state in alternate location

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This provides a facility which is intended for use by KVM, where the
contents of the FP/VSX and VMX (Altivec) registers can be saved away
to somewhere other than the thread_struct when kernel code wants to
use floating point or VMX instructions.  This is done by providing a
pointer in the thread_struct to indicate where the state should be
saved to.  The giveup_fpu() and giveup_altivec() functions test these
pointers and save state to the indicated location if they are non-NULL.
Note that the MSR_FP/VEC bits in task->thread.regs->msr are still used
to indicate whether the CPU register state is live, even when an
alternate save location is being used.

This also provides load_fp_state() and load_vr_state() functions, which
load up FP/VSX and VMX state from memory into the CPU registers, and
corresponding store_fp_state() and store_vr_state() functions, which
store FP/VSX and VMX state into memory from the CPU registers.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Paul Mackerras
2013-09-10 20:21:10 +10:00
committed by Benjamin Herrenschmidt
parent de79f7b9f6
commit 18461960cb
6 changed files with 71 additions and 3 deletions
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29
arch/powerpc/kernel/vector.S
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@@ -36,6 +36,28 @@ _GLOBAL(do_load_up_transact_altivec)
blr
#endif
/*
* Load state from memory into VMX registers including VSCR.
* Assumes the caller has enabled VMX in the MSR.
*/
_GLOBAL(load_vr_state)
li r4,VRSTATE_VSCR
lvx vr0,r4,r3
mtvscr vr0
REST_32VRS(0,r4,r3)
blr
/*
* Store VMX state into memory, including VSCR.
* Assumes the caller has enabled VMX in the MSR.
*/
_GLOBAL(store_vr_state)
SAVE_32VRS(0, r4, r3)
mfvscr vr0
li r4, VRSTATE_VSCR
stvx vr0, r4, r3
blr
/*
* Disable VMX for the task which had it previously,
* and save its vector registers in its thread_struct.
@@ -144,9 +166,12 @@ _GLOBAL(giveup_altivec)
PPC_LCMPI 0,r3,0
beqlr /* if no previous owner, done */
addi r3,r3,THREAD /* want THREAD of task */
addi r7,r3,THREAD_VRSTATE
PPC_LL r7,THREAD_VRSAVEAREA(r3)
PPC_LL r5,PT_REGS(r3)
PPC_LCMPI 0,r5,0
PPC_LCMPI 0,r7,0
bne 2f
addi r7,r3,THREAD_VRSTATE
2: PPC_LCMPI 0,r5,0
SAVE_32VRS(0,r4,r7)
mfvscr vr0
li r4,VRSTATE_VSCR