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linux/arch/mips/kvm/fpu.S

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MIPS: KVM: Add base guest FPU support Add base code for supporting FPU in MIPS KVM guests. The FPU cannot yet be enabled in the guest, we're just laying the groundwork. Whether the guest's FPU context is loaded is stored in a bit in the fpu_inuse vcpu member. This allows the FPU to be disabled when the guest disables it, but keeping the FPU context loaded so it doesn't have to be reloaded if the guest re-enables it. An fpu_enabled vcpu member stores whether userland has enabled the FPU capability (which will be wired up in a later patch). New assembly code is added for saving and restoring the FPU context, and for saving/clearing and restoring FCSR (which can itself cause an FP exception depending on the value). The FCSR is restored before returning to the guest if the FPU is already enabled, and a die notifier is registered to catch the possible FP exception and step over the ctc1 instruction. The helper function kvm_lose_fpu() is added to save FPU context and disable the FPU, which is used when saving hardware state before a context switch or KVM exit (the vcpu_get_regs() callback). The helper function kvm_own_fpu() is added to enable the FPU and restore the FPU context if it isn't already loaded, which will be used in a later patch when the guest attempts to use the FPU for the first time and triggers a co-processor unusable exception. The helper function kvm_drop_fpu() is added to discard the FPU context and disable the FPU, which will be used in a later patch when the FPU state will become architecturally UNPREDICTABLE (change of FR mode) to force a reload of [stale] context in the new FR mode. 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
2014-11-18 22:09:12 +08:00
/*
* 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.
*
* FPU context handling code for KVM.
*
* Copyright (C) 2015 Imagination Technologies Ltd.
*/
#include <asm/asm.h>
#include <asm/asm-offsets.h>
#include <asm/fpregdef.h>
#include <asm/mipsregs.h>
#include <asm/regdef.h>
.set noreorder
.set noat
LEAF(__kvm_save_fpu)
.set push
.set mips64r2
SET_HARDFLOAT
mfc0 t0, CP0_STATUS
sll t0, t0, 5 # is Status.FR set?
bgez t0, 1f # no: skip odd doubles
nop
sdc1 $f1, VCPU_FPR1(a0)
sdc1 $f3, VCPU_FPR3(a0)
sdc1 $f5, VCPU_FPR5(a0)
sdc1 $f7, VCPU_FPR7(a0)
sdc1 $f9, VCPU_FPR9(a0)
sdc1 $f11, VCPU_FPR11(a0)
sdc1 $f13, VCPU_FPR13(a0)
sdc1 $f15, VCPU_FPR15(a0)
sdc1 $f17, VCPU_FPR17(a0)
sdc1 $f19, VCPU_FPR19(a0)
sdc1 $f21, VCPU_FPR21(a0)
sdc1 $f23, VCPU_FPR23(a0)
sdc1 $f25, VCPU_FPR25(a0)
sdc1 $f27, VCPU_FPR27(a0)
sdc1 $f29, VCPU_FPR29(a0)
sdc1 $f31, VCPU_FPR31(a0)
1: sdc1 $f0, VCPU_FPR0(a0)
sdc1 $f2, VCPU_FPR2(a0)
sdc1 $f4, VCPU_FPR4(a0)
sdc1 $f6, VCPU_FPR6(a0)
sdc1 $f8, VCPU_FPR8(a0)
sdc1 $f10, VCPU_FPR10(a0)
sdc1 $f12, VCPU_FPR12(a0)
sdc1 $f14, VCPU_FPR14(a0)
sdc1 $f16, VCPU_FPR16(a0)
sdc1 $f18, VCPU_FPR18(a0)
sdc1 $f20, VCPU_FPR20(a0)
sdc1 $f22, VCPU_FPR22(a0)
sdc1 $f24, VCPU_FPR24(a0)
sdc1 $f26, VCPU_FPR26(a0)
sdc1 $f28, VCPU_FPR28(a0)
jr ra
sdc1 $f30, VCPU_FPR30(a0)
.set pop
END(__kvm_save_fpu)
LEAF(__kvm_restore_fpu)
.set push
.set mips64r2
SET_HARDFLOAT
mfc0 t0, CP0_STATUS
sll t0, t0, 5 # is Status.FR set?
bgez t0, 1f # no: skip odd doubles
nop
ldc1 $f1, VCPU_FPR1(a0)
ldc1 $f3, VCPU_FPR3(a0)
ldc1 $f5, VCPU_FPR5(a0)
ldc1 $f7, VCPU_FPR7(a0)
ldc1 $f9, VCPU_FPR9(a0)
ldc1 $f11, VCPU_FPR11(a0)
ldc1 $f13, VCPU_FPR13(a0)
ldc1 $f15, VCPU_FPR15(a0)
ldc1 $f17, VCPU_FPR17(a0)
ldc1 $f19, VCPU_FPR19(a0)
ldc1 $f21, VCPU_FPR21(a0)
ldc1 $f23, VCPU_FPR23(a0)
ldc1 $f25, VCPU_FPR25(a0)
ldc1 $f27, VCPU_FPR27(a0)
ldc1 $f29, VCPU_FPR29(a0)
ldc1 $f31, VCPU_FPR31(a0)
1: ldc1 $f0, VCPU_FPR0(a0)
ldc1 $f2, VCPU_FPR2(a0)
ldc1 $f4, VCPU_FPR4(a0)
ldc1 $f6, VCPU_FPR6(a0)
ldc1 $f8, VCPU_FPR8(a0)
ldc1 $f10, VCPU_FPR10(a0)
ldc1 $f12, VCPU_FPR12(a0)
ldc1 $f14, VCPU_FPR14(a0)
ldc1 $f16, VCPU_FPR16(a0)
ldc1 $f18, VCPU_FPR18(a0)
ldc1 $f20, VCPU_FPR20(a0)
ldc1 $f22, VCPU_FPR22(a0)
ldc1 $f24, VCPU_FPR24(a0)
ldc1 $f26, VCPU_FPR26(a0)
ldc1 $f28, VCPU_FPR28(a0)
jr ra
ldc1 $f30, VCPU_FPR30(a0)
.set pop
END(__kvm_restore_fpu)
LEAF(__kvm_restore_fcsr)
.set push
SET_HARDFLOAT
lw t0, VCPU_FCR31(a0)
/*
* The ctc1 must stay at this offset in __kvm_restore_fcsr.
* See kvm_mips_csr_die_notify() which handles t0 containing a value
* which triggers an FP Exception, which must be stepped over and
* ignored since the set cause bits must remain there for the guest.
*/
ctc1 t0, fcr31
jr ra
nop
.set pop
END(__kvm_restore_fcsr)