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linux/arch/mips/kvm/msa.S
James Hogan 539cb89fbd MIPS: KVM: Add base guest MSA support 
Add base code for supporting the MIPS SIMD Architecture (MSA) in MIPS
KVM guests. MSA cannot yet be enabled in the guest, we're just laying
the groundwork.

As with the FPU, whether the guest's MSA context is loaded is stored in
another bit in the fpu_inuse vcpu member. This allows MSA to be disabled
when the guest disables it, but keeping the MSA context loaded so it
doesn't have to be reloaded if the guest re-enables it.

New assembly code is added for saving and restoring the MSA context,
restoring only the upper half of the MSA context (for if the FPU context
is already loaded) and for saving/clearing and restoring MSACSR (which
can itself cause an MSA FP exception depending on the value). The MSACSR
is restored before returning to the guest if MSA is already enabled, and
the existing FP exception die notifier is extended to catch the possible
MSA FP exception and step over the ctcmsa instruction.

The helper function kvm_own_msa() is added to enable MSA and restore
the MSA context if it isn't already loaded, which will be used in a
later patch when the guest attempts to use MSA for the first time and
triggers an MSA disabled exception.

The existing FPU helpers are extended to handle MSA. kvm_lose_fpu()
saves the full MSA context if it is loaded (which includes the FPU
context) and both kvm_lose_fpu() and kvm_drop_fpu() disable MSA.

kvm_own_fpu() also needs to lose any MSA context if FR=0, since there
would be a risk of getting reserved instruction exceptions if CU1 is
enabled and we later try and save the MSA context. We shouldn't usually
hit this case since it will be handled when emulating CU1 changes,
however there's nothing to stop the guest modifying the Status register
directly via the comm page, which will cause this case to get hit.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
2015-03-27 21:25:19 +00:00

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/*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* MIPS SIMD Architecture (MSA) context handling code for KVM.
*
* Copyright (C) 2015 Imagination Technologies Ltd.
*/
#include <asm/asm.h>
#include <asm/asm-offsets.h>
#include <asm/asmmacro.h>
#include <asm/regdef.h>
.set noreorder
.set noat
LEAF(__kvm_save_msa)
st_d 0, VCPU_FPR0, a0
st_d 1, VCPU_FPR1, a0
st_d 2, VCPU_FPR2, a0
st_d 3, VCPU_FPR3, a0
st_d 4, VCPU_FPR4, a0
st_d 5, VCPU_FPR5, a0
st_d 6, VCPU_FPR6, a0
st_d 7, VCPU_FPR7, a0
st_d 8, VCPU_FPR8, a0
st_d 9, VCPU_FPR9, a0
st_d 10, VCPU_FPR10, a0
st_d 11, VCPU_FPR11, a0
st_d 12, VCPU_FPR12, a0
st_d 13, VCPU_FPR13, a0
st_d 14, VCPU_FPR14, a0
st_d 15, VCPU_FPR15, a0
st_d 16, VCPU_FPR16, a0
st_d 17, VCPU_FPR17, a0
st_d 18, VCPU_FPR18, a0
st_d 19, VCPU_FPR19, a0
st_d 20, VCPU_FPR20, a0
st_d 21, VCPU_FPR21, a0
st_d 22, VCPU_FPR22, a0
st_d 23, VCPU_FPR23, a0
st_d 24, VCPU_FPR24, a0
st_d 25, VCPU_FPR25, a0
st_d 26, VCPU_FPR26, a0
st_d 27, VCPU_FPR27, a0
st_d 28, VCPU_FPR28, a0
st_d 29, VCPU_FPR29, a0
st_d 30, VCPU_FPR30, a0
st_d 31, VCPU_FPR31, a0
jr ra
nop
END(__kvm_save_msa)
LEAF(__kvm_restore_msa)
ld_d 0, VCPU_FPR0, a0
ld_d 1, VCPU_FPR1, a0
ld_d 2, VCPU_FPR2, a0
ld_d 3, VCPU_FPR3, a0
ld_d 4, VCPU_FPR4, a0
ld_d 5, VCPU_FPR5, a0
ld_d 6, VCPU_FPR6, a0
ld_d 7, VCPU_FPR7, a0
ld_d 8, VCPU_FPR8, a0
ld_d 9, VCPU_FPR9, a0
ld_d 10, VCPU_FPR10, a0
ld_d 11, VCPU_FPR11, a0
ld_d 12, VCPU_FPR12, a0
ld_d 13, VCPU_FPR13, a0
ld_d 14, VCPU_FPR14, a0
ld_d 15, VCPU_FPR15, a0
ld_d 16, VCPU_FPR16, a0
ld_d 17, VCPU_FPR17, a0
ld_d 18, VCPU_FPR18, a0
ld_d 19, VCPU_FPR19, a0
ld_d 20, VCPU_FPR20, a0
ld_d 21, VCPU_FPR21, a0
ld_d 22, VCPU_FPR22, a0
ld_d 23, VCPU_FPR23, a0
ld_d 24, VCPU_FPR24, a0
ld_d 25, VCPU_FPR25, a0
ld_d 26, VCPU_FPR26, a0
ld_d 27, VCPU_FPR27, a0
ld_d 28, VCPU_FPR28, a0
ld_d 29, VCPU_FPR29, a0
ld_d 30, VCPU_FPR30, a0
ld_d 31, VCPU_FPR31, a0
jr ra
nop
END(__kvm_restore_msa)
.macro kvm_restore_msa_upper wr, off, base
.set push
.set noat
#ifdef CONFIG_64BIT
ld $1, \off(\base)
insert_d \wr, 1
#elif defined(CONFIG_CPU_LITTLE_ENDIAN)
lw $1, \off(\base)
insert_w \wr, 2
lw $1, (\off+4)(\base)
insert_w \wr, 3
#else /* CONFIG_CPU_BIG_ENDIAN */
lw $1, (\off+4)(\base)
insert_w \wr, 2
lw $1, \off(\base)
insert_w \wr, 3
#endif
.set pop
.endm
LEAF(__kvm_restore_msa_upper)
kvm_restore_msa_upper 0, VCPU_FPR0 +8, a0
kvm_restore_msa_upper 1, VCPU_FPR1 +8, a0
kvm_restore_msa_upper 2, VCPU_FPR2 +8, a0
kvm_restore_msa_upper 3, VCPU_FPR3 +8, a0
kvm_restore_msa_upper 4, VCPU_FPR4 +8, a0
kvm_restore_msa_upper 5, VCPU_FPR5 +8, a0
kvm_restore_msa_upper 6, VCPU_FPR6 +8, a0
kvm_restore_msa_upper 7, VCPU_FPR7 +8, a0
kvm_restore_msa_upper 8, VCPU_FPR8 +8, a0
kvm_restore_msa_upper 9, VCPU_FPR9 +8, a0
kvm_restore_msa_upper 10, VCPU_FPR10+8, a0
kvm_restore_msa_upper 11, VCPU_FPR11+8, a0
kvm_restore_msa_upper 12, VCPU_FPR12+8, a0
kvm_restore_msa_upper 13, VCPU_FPR13+8, a0
kvm_restore_msa_upper 14, VCPU_FPR14+8, a0
kvm_restore_msa_upper 15, VCPU_FPR15+8, a0
kvm_restore_msa_upper 16, VCPU_FPR16+8, a0
kvm_restore_msa_upper 17, VCPU_FPR17+8, a0
kvm_restore_msa_upper 18, VCPU_FPR18+8, a0
kvm_restore_msa_upper 19, VCPU_FPR19+8, a0
kvm_restore_msa_upper 20, VCPU_FPR20+8, a0
kvm_restore_msa_upper 21, VCPU_FPR21+8, a0
kvm_restore_msa_upper 22, VCPU_FPR22+8, a0
kvm_restore_msa_upper 23, VCPU_FPR23+8, a0
kvm_restore_msa_upper 24, VCPU_FPR24+8, a0
kvm_restore_msa_upper 25, VCPU_FPR25+8, a0
kvm_restore_msa_upper 26, VCPU_FPR26+8, a0
kvm_restore_msa_upper 27, VCPU_FPR27+8, a0
kvm_restore_msa_upper 28, VCPU_FPR28+8, a0
kvm_restore_msa_upper 29, VCPU_FPR29+8, a0
kvm_restore_msa_upper 30, VCPU_FPR30+8, a0
kvm_restore_msa_upper 31, VCPU_FPR31+8, a0
jr ra
nop
END(__kvm_restore_msa_upper)
LEAF(__kvm_restore_msacsr)
lw t0, VCPU_MSA_CSR(a0)
/*
* The ctcmsa must stay at this offset in __kvm_restore_msacsr.
* See kvm_mips_csr_die_notify() which handles t0 containing a value
* which triggers an MSA FP Exception, which must be stepped over and
* ignored since the set cause bits must remain there for the guest.
*/
_ctcmsa MSA_CSR, t0
jr ra
nop
END(__kvm_restore_msacsr)
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