[PATCH 12/21] arm64: KVM: Implement fpsimd save/restore
Steve Capper
steve.capper at linaro.org
Tue Nov 17 03:13:18 PST 2015
On 16 November 2015 at 13:11, Marc Zyngier <marc.zyngier at arm.com> wrote:
> Implement the fpsimd save restore, keeping the lazy part in
> assembler (as returning to C would be overkill).
>
> Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
> ---
> arch/arm64/kvm/hyp/Makefile | 1 +
> arch/arm64/kvm/hyp/entry.S | 32 +++++++++++++++++++++++++++++++-
> arch/arm64/kvm/hyp/fpsimd.S | 33 +++++++++++++++++++++++++++++++++
> arch/arm64/kvm/hyp/hyp.h | 3 +++
> arch/arm64/kvm/hyp/switch.c | 8 ++++++++
> 5 files changed, 76 insertions(+), 1 deletion(-)
> create mode 100644 arch/arm64/kvm/hyp/fpsimd.S
>
> diff --git a/arch/arm64/kvm/hyp/Makefile b/arch/arm64/kvm/hyp/Makefile
> index 9c11b0f..56238d0 100644
> --- a/arch/arm64/kvm/hyp/Makefile
> +++ b/arch/arm64/kvm/hyp/Makefile
> @@ -9,3 +9,4 @@ obj-$(CONFIG_KVM_ARM_HOST) += sysreg-sr.o
> obj-$(CONFIG_KVM_ARM_HOST) += debug-sr.o
> obj-$(CONFIG_KVM_ARM_HOST) += entry.o
> obj-$(CONFIG_KVM_ARM_HOST) += switch.o
> +obj-$(CONFIG_KVM_ARM_HOST) += fpsimd.o
> diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
> index 2c4449a..7552922 100644
> --- a/arch/arm64/kvm/hyp/entry.S
> +++ b/arch/arm64/kvm/hyp/entry.S
> @@ -27,6 +27,7 @@
>
> #define CPU_GP_REG_OFFSET(x) (CPU_GP_REGS + x)
> #define CPU_XREG_OFFSET(x) CPU_GP_REG_OFFSET(CPU_USER_PT_REGS + 8*x)
> +#define CPU_SYSREG_OFFSET(x) (CPU_SYSREGS + 8*x)
>
> .text
> .pushsection .hyp.text, "ax"
> @@ -152,4 +153,33 @@ ENTRY(__guest_exit)
> ret
> ENDPROC(__guest_exit)
>
> - /* Insert fault handling here */
> +ENTRY(__fpsimd_guest_restore)
> + push x4, lr
> +
> + mrs x2, cptr_el2
> + bic x2, x2, #CPTR_EL2_TFP
> + msr cptr_el2, x2
> + isb
> +
> + mrs x3, tpidr_el2
> +
> + ldr x0, [x3, #VCPU_HOST_CONTEXT]
> + kern_hyp_va x0
> + add x0, x0, #CPU_GP_REG_OFFSET(CPU_FP_REGS)
> + bl __fpsimd_save_state
> +
> + add x2, x3, #VCPU_CONTEXT
> + add x0, x2, #CPU_GP_REG_OFFSET(CPU_FP_REGS)
> + bl __fpsimd_restore_state
> +
> + mrs x1, hcr_el2
> + tbnz x1, #HCR_RW_SHIFT, 1f
> + ldr x4, [x2, #CPU_SYSREG_OFFSET(FPEXC32_EL2)]
> + msr fpexc32_el2, x4
> +1:
> + pop x4, lr
> + pop x2, x3
> + pop x0, x1
> +
> + eret
> +ENDPROC(__fpsimd_guest_restore)
> diff --git a/arch/arm64/kvm/hyp/fpsimd.S b/arch/arm64/kvm/hyp/fpsimd.S
> new file mode 100644
> index 0000000..da3f22c
> --- /dev/null
> +++ b/arch/arm64/kvm/hyp/fpsimd.S
> @@ -0,0 +1,33 @@
> +/*
> + * Copyright (C) 2015 - ARM Ltd
> + * Author: Marc Zyngier <marc.zyngier at arm.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program. If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include <linux/linkage.h>
> +
> +#include <asm/fpsimdmacros.h>
> +
> + .text
> + .pushsection .hyp.text, "ax"
> +
> +ENTRY(__fpsimd_save_state)
> + fpsimd_save x0, 1
> + ret
> +ENDPROC(__fpsimd_save_state)
> +
> +ENTRY(__fpsimd_restore_state)
> + fpsimd_restore x0, 1
> + ret
> +ENDPROC(__fpsimd_restore_state)
> diff --git a/arch/arm64/kvm/hyp/hyp.h b/arch/arm64/kvm/hyp/hyp.h
> index bf13238..240fb79 100644
> --- a/arch/arm64/kvm/hyp/hyp.h
> +++ b/arch/arm64/kvm/hyp/hyp.h
> @@ -70,6 +70,9 @@ void __debug_clear_restore_state(struct kvm_vcpu *vcpu,
> struct kvm_guest_debug_arch *dbg,
> struct kvm_cpu_context *ctxt);
>
> +void __fpsimd_save_state(struct user_fpsimd_state *fp_regs);
> +void __fpsimd_restore_state(struct user_fpsimd_state *fp_regs);
> +
> u64 __guest_enter(struct kvm_vcpu *vcpu, struct kvm_cpu_context *host_ctxt);
>
> #endif /* __ARM64_KVM_HYP_H__ */
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index a3af81a..06d3e20 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -88,6 +88,7 @@ int __hyp_text __guest_run(struct kvm_vcpu *vcpu)
> {
> struct kvm_cpu_context *host_ctxt;
> struct kvm_cpu_context *guest_ctxt;
> + bool fp_enabled;
> u64 exit_code;
>
> vcpu = kern_hyp_va(vcpu);
> @@ -117,6 +118,8 @@ int __hyp_text __guest_run(struct kvm_vcpu *vcpu)
> exit_code = __guest_enter(vcpu, host_ctxt);
> /* And we're baaack! */
>
> + fp_enabled = !!(read_sysreg(cptr_el2) & CPTR_EL2_TFP);
Should this not be a single logical not?
If CPTR_EL2_TFP is set then the floating point will trap in the guest,
thus floating point hasn't been used by the guest?
I am chasing some issues when running kvmtool on my system with this
patch set applied.
The above change stops NetworkManager crashing on my host.
Unfortunately I am still chasing some problems with the guest (illegal
instructions).
> +
> __sysreg_save_state(guest_ctxt);
> __sysreg32_save_state(vcpu);
> __timer_save_state(vcpu);
> @@ -127,6 +130,11 @@ int __hyp_text __guest_run(struct kvm_vcpu *vcpu)
>
> __sysreg_restore_state(host_ctxt);
>
> + if (fp_enabled) {
> + __fpsimd_save_state(&guest_ctxt->gp_regs.fp_regs);
> + __fpsimd_restore_state(&host_ctxt->gp_regs.fp_regs);
> + }
> +
> __debug_save_state(vcpu, &vcpu->arch.vcpu_debug_state, guest_ctxt);
> __debug_clear_restore_state(vcpu, &vcpu->arch.host_debug_state, host_ctxt);
>
> --
> 2.1.4
>
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> kvmarm at lists.cs.columbia.edu
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