Subject: [PATCH v3 06/22] arm64: KVM: Implement timer save/restore

From: [email-masked] (Marc Zyngier)
Date: Tue, 08 Dec 2015 10:02:59 +0000

On 08/12/15 02:18, Mario Smarduch wrote:
> 
> 
> On 12/7/2015 2:53 AM, Marc Zyngier wrote:
>> Implement the timer save restore as a direct translation of
>> the assembly code version.
>>
>> Signed-off-by: Marc Zyngier <[email-masked]>
>> ---
>>  arch/arm64/kvm/hyp/Makefile          |  1 +
>>  arch/arm64/kvm/hyp/hyp.h             |  3 ++
>>  arch/arm64/kvm/hyp/timer-sr.c        | 72 ++++++++++++++++++++++++++++++++++++
>>  include/clocksource/arm_arch_timer.h |  6 +++
>>  4 files changed, 82 insertions(+)
>>  create mode 100644 arch/arm64/kvm/hyp/timer-sr.c
>>
>> diff --git a/arch/arm64/kvm/hyp/Makefile b/arch/arm64/kvm/hyp/Makefile
>> index d1e38ce..455dc0a 100644
>> --- a/arch/arm64/kvm/hyp/Makefile
>> +++ b/arch/arm64/kvm/hyp/Makefile
>> @@ -4,3 +4,4 @@
>>  
>>  obj-$(CONFIG_KVM_ARM_HOST) += vgic-v2-sr.o
>>  obj-$(CONFIG_KVM_ARM_HOST) += vgic-v3-sr.o
>> +obj-$(CONFIG_KVM_ARM_HOST) += timer-sr.o
>> diff --git a/arch/arm64/kvm/hyp/hyp.h b/arch/arm64/kvm/hyp/hyp.h
>> index 5759f9f..f213e46 100644
>> --- a/arch/arm64/kvm/hyp/hyp.h
>> +++ b/arch/arm64/kvm/hyp/hyp.h
>> @@ -35,5 +35,8 @@ void __vgic_v2_restore_state(struct kvm_vcpu *vcpu);
>>  void __vgic_v3_save_state(struct kvm_vcpu *vcpu);
>>  void __vgic_v3_restore_state(struct kvm_vcpu *vcpu);
>>  
>> +void __timer_save_state(struct kvm_vcpu *vcpu);
>> +void __timer_restore_state(struct kvm_vcpu *vcpu);
>> +
>>  #endif /* __ARM64_KVM_HYP_H__ */
>>  
>> diff --git a/arch/arm64/kvm/hyp/timer-sr.c b/arch/arm64/kvm/hyp/timer-sr.c
>> new file mode 100644
>> index 0000000..67292c0
>> --- /dev/null
>> +++ b/arch/arm64/kvm/hyp/timer-sr.c
>> @@ -0,0 +1,72 @@
>> +/*
>> + * Copyright (C) 2012-2015 - ARM Ltd
>> + * Author: Marc Zyngier <[email-masked]>
>> + *
>> + * 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 <clocksource/arm_arch_timer.h>
>> +#include <linux/compiler.h>
>> +#include <linux/kvm_host.h>
>> +
>> +#include <asm/kvm_mmu.h>
>> +
>> +#include "hyp.h"
>> +
>> +/* vcpu is already in the HYP VA space */
>> +void __hyp_text __timer_save_state(struct kvm_vcpu *vcpu)
>> +{
>> +	struct kvm *kvm = kern_hyp_va(vcpu->kvm);
>> +	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
>> +	u64 val;
>> +
>> +	if (kvm->arch.timer.enabled) {
>> +		timer->cntv_ctl = read_sysreg(cntv_ctl_el0);
>> +		isb();
> 
> Can you share the subtle insight why is the isb() needed here?
> B2.7.3 mentions changes to system registers only.

This is actually a leftover of some previous code rework in the assembly
version of this code, which has found its way into the new
implementation. Duh.

Thanks for pointing this out.

	M.
-- 
Jazz is not dead. It just smells funny...