linux-kernel - Re: [PATCH 5/6] Try using new kvm clock msrs

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Message-ID: <20100427133543.GD18410@amt.cnet>
Date:	Tue, 27 Apr 2010 10:35:43 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Glauber Costa <glommer@...hat.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, avi@...hat.com
Subject: Re: [PATCH 5/6] Try using new kvm clock msrs

On Mon, Apr 26, 2010 at 01:46:27PM -0400, Glauber Costa wrote:
> We now added a new set of clock-related msrs in replacement of the old
> ones. In theory, we could just try to use them and get a return value
> indicating they do not exist, due to our use of kvm_write_msr_save.
> 
> However, kvm clock registration happens very early, and if we ever
> try to write to a non-existant MSR, we raise a lethal #GP, since our
> idt handlers are not in place yet.
> 
> So this patch tests for a cpuid feature exported by the host to
> decide which set of msrs are supported.
> 
> Signed-off-by: Glauber Costa <glommer@...hat.com>
> ---
>  arch/x86/kernel/kvmclock.c |   56 +++++++++++++++++++++++++++----------------
>  1 files changed, 35 insertions(+), 21 deletions(-)
> 
> diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
> index feaeb0d..f2f6aee 100644
> --- a/arch/x86/kernel/kvmclock.c
> +++ b/arch/x86/kernel/kvmclock.c
> @@ -29,6 +29,8 @@
>  #define KVM_SCALE 22
>  
>  static int kvmclock = 1;
> +static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
> +static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
>  
>  static int parse_no_kvmclock(char *arg)
>  {
> @@ -41,6 +43,7 @@ early_param("no-kvmclock", parse_no_kvmclock);
>  static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock);
>  static struct pvclock_wall_clock wall_clock;
>  
> +

Extra newline.

>  /*
>   * The wallclock is the time of day when we booted. Since then, some time may
>   * have elapsed since the hypervisor wrote the data. So we try to account for
> @@ -54,7 +57,8 @@ static unsigned long kvm_get_wallclock(void)
>  
>  	low = (int)__pa_symbol(&wall_clock);
>  	high = ((u64)__pa_symbol(&wall_clock) >> 32);
> -	native_write_msr(MSR_KVM_WALL_CLOCK, low, high);
> +
> +	native_write_msr_safe(msr_kvm_wall_clock, low, high);
>  
>  	vcpu_time = &get_cpu_var(hv_clock);
>  	pvclock_read_wallclock(&wall_clock, vcpu_time, &ts);
> @@ -130,7 +134,8 @@ static int kvm_register_clock(char *txt)
>  	high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32);
>  	printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
>  	       cpu, high, low, txt);
> -	return native_write_msr_safe(MSR_KVM_SYSTEM_TIME, low, high);
> +
> +	return native_write_msr_safe(msr_kvm_system_time, low, high);
>  }
>  
>  #ifdef CONFIG_X86_LOCAL_APIC
> @@ -165,14 +170,15 @@ static void __init kvm_smp_prepare_boot_cpu(void)
>  #ifdef CONFIG_KEXEC
>  static void kvm_crash_shutdown(struct pt_regs *regs)
>  {
> -	native_write_msr_safe(MSR_KVM_SYSTEM_TIME, 0, 0);
> +
> +	native_write_msr(msr_kvm_system_time, 0, 0);
>  	native_machine_crash_shutdown(regs);
>  }
>  #endif
>  
>  static void kvm_shutdown(void)
>  {
> -	native_write_msr_safe(MSR_KVM_SYSTEM_TIME, 0, 0);
> +	native_write_msr(msr_kvm_system_time, 0, 0);
>  	native_machine_shutdown();
>  }
>  
> @@ -181,27 +187,35 @@ void __init kvmclock_init(void)
>  	if (!kvm_para_available())
>  		return;
>  
> -	if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) {
> -		if (kvm_register_clock("boot clock"))
> -			return;
> -		pv_time_ops.sched_clock = kvm_clock_read;
> -		x86_platform.calibrate_tsc = kvm_get_tsc_khz;
> -		x86_platform.get_wallclock = kvm_get_wallclock;
> -		x86_platform.set_wallclock = kvm_set_wallclock;
> +	if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
> +		msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
> +		msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
> +	}
> +	else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)))
> +		return;

Non conformant indentation.

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