[PATCH 12/21] arm64: KVM: Implement fpsimd save/restore
Steve Capper
steve.capper at linaro.org
Tue Nov 17 03:49:13 PST 2015
On 17 November 2015 at 11:25, Marc Zyngier <marc.zyngier at arm.com> wrote:
> On 17/11/15 11:13, Steve Capper wrote:
>> 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).
>
> Yeah, it looks like I screwed up in the base code, and somewhat fixed it
> in the VHE branch... And as I'm testing the full setup, I didn't spot
> it, sorry.
>
> Can you please give the kvm-arm64/vhe-wsinc branch a spin and let me
> know if it works for you?
Thanks Marc,
kvm-arm64/vhe-wsinc works well on my test system.
Cheers,
--
Steve
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