linux-kernel - Re: [PATCH v2 1/6] KVM: arm/arm64: arch_timer: Gather KVM specific information in a structure

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Message-ID: <56C6C318.3000205@redhat.com>
Date:	Fri, 19 Feb 2016 01:24:08 -0600
From:	Wei Huang <wei@...hat.com>
To:	Julien Grall <julien.grall@....com>, kvmarm@...ts.cs.columbia.edu
Cc:	christoffer.dall@...aro.org, marc.zyngier@....com,
	fu.wei@...aro.org, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	al.stone@...aro.org, Daniel Lezcano <daniel.lezcano@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Gleb Natapov <gleb@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH v2 1/6] KVM: arm/arm64: arch_timer: Gather KVM specific
 information in a structure



On 02/11/2016 09:33 AM, Julien Grall wrote:
> Introduce a structure which are filled up by the arch timer driver and
> used by the virtual timer in KVM.
> 
> The first member of this structure will be the timecounter. More members
> will be added later.
> 
> This is also dropping arch_timer_get_timecounter as it was only used by
> the KVM code. Furthermore, a stub for the new helper hasn't been
> introduced because KVM is requiring the arch timer for both ARM64 and
> ARM32.
> 
> Signed-off-by: Julien Grall <julien.grall@....com>
> 
> ---
> Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Christoffer Dall <christoffer.dall@...aro.org>
> Cc: Marc Zyngier <marc.zyngier@....com>
> Cc: Gleb Natapov <gleb@...nel.org>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  drivers/clocksource/arm_arch_timer.c |  9 +++++----
>  include/clocksource/arm_arch_timer.h | 12 ++++++------
>  virt/kvm/arm/arch_timer.c            |  6 +++---
>  3 files changed, 14 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
> index c64d543..6eb2c5d 100644
> --- a/drivers/clocksource/arm_arch_timer.c
> +++ b/drivers/clocksource/arm_arch_timer.c
> @@ -447,11 +447,11 @@ static struct cyclecounter cyclecounter = {
>  	.mask	= CLOCKSOURCE_MASK(56),
>  };
>  
> -static struct timecounter timecounter;
> +static struct arch_timer_kvm_info arch_timer_kvm_info;
>  
> -struct timecounter *arch_timer_get_timecounter(void)
> +struct arch_timer_kvm_info *arch_timer_get_kvm_info(void)
>  {
> -	return &timecounter;
> +	return &arch_timer_kvm_info;
>  }
>  
>  static void __init arch_counter_register(unsigned type)
> @@ -479,7 +479,8 @@ static void __init arch_counter_register(unsigned type)
>  	clocksource_register_hz(&clocksource_counter, arch_timer_rate);
>  	cyclecounter.mult = clocksource_counter.mult;
>  	cyclecounter.shift = clocksource_counter.shift;
> -	timecounter_init(&timecounter, &cyclecounter, start_count);
> +	timecounter_init(&arch_timer_kvm_info.timecounter,
> +			 &cyclecounter, start_count);
>  
>  	/* 56 bits minimum, so we assume worst case rollover */
>  	sched_clock_register(arch_timer_read_counter, 56, arch_timer_rate);
> diff --git a/include/clocksource/arm_arch_timer.h b/include/clocksource/arm_arch_timer.h
> index 25d0914..4d487f8 100644
> --- a/include/clocksource/arm_arch_timer.h
> +++ b/include/clocksource/arm_arch_timer.h
> @@ -49,11 +49,16 @@ enum arch_timer_reg {
>  
>  #define ARCH_TIMER_EVT_STREAM_FREQ	10000	/* 100us */
>  
> +struct arch_timer_kvm_info {
> +	struct timecounter timecounter;
> +};
> +
>  #ifdef CONFIG_ARM_ARCH_TIMER
>  
>  extern u32 arch_timer_get_rate(void);
>  extern u64 (*arch_timer_read_counter)(void);
> -extern struct timecounter *arch_timer_get_timecounter(void);
> +
> +extern struct arch_timer_kvm_info *arch_timer_get_kvm_info(void);
>  
>  #else
>  
> @@ -67,11 +72,6 @@ static inline u64 arch_timer_read_counter(void)
>  	return 0;
>  }
>  
> -static inline struct timecounter *arch_timer_get_timecounter(void)
> -{
> -	return NULL;
> -}
> -

Most parts are OK. Regarding removing this function from the #else area,
is there a possibility to have CONFIG_ARM_ARCH_TIMER=n and CONFIG_KVM=y.
If so, will the compilation fails here?

-Wei

>  #endif
>  
>  #endif
> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
> index 69bca18..a669c6a 100644
> --- a/virt/kvm/arm/arch_timer.c
> +++ b/virt/kvm/arm/arch_timer.c
> @@ -385,11 +385,11 @@ int kvm_timer_hyp_init(void)
>  {
>  	struct device_node *np;
>  	unsigned int ppi;
> +	struct arch_timer_kvm_info *info;
>  	int err;
>  
> -	timecounter = arch_timer_get_timecounter();
> -	if (!timecounter)
> -		return -ENODEV;
> +	info = arch_timer_get_kvm_info();
> +	timecounter = &info->timecounter;
>  
>  	np = of_find_matching_node(NULL, arch_timer_of_match);
>  	if (!np) {
>