Re: [PATCH 1/2] kvmclock - the host part.

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Glauber de Oliveira Costa wrote:
> This is the host part of kvm clocksource implementation. As it does
> not include clockevents, it is a fairly simple implementation. We
> only have to register a per-vcpu area, and start writting to it periodically.
>
> The area is binary compatible with xen, as we use the same shadow_info structure.
>
> Signed-off-by: Glauber de Oliveira Costa <gcosta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> ---
>  arch/x86/kvm/x86.c         |   98 +++++++++++++++++++++++++++++++++++++++++++-
>  include/asm-x86/kvm_host.h |    6 +++
>  include/asm-x86/kvm_para.h |   24 +++++++++++
>  include/linux/kvm.h        |    1 +
>  4 files changed, 128 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 8a90403..fd69aa1 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -19,6 +19,7 @@
>  #include "irq.h"
>  #include "mmu.h"
>  
> +#include <linux/clocksource.h>
>  #include <linux/kvm.h>
>  #include <linux/fs.h>
>  #include <linux/vmalloc.h>
> @@ -412,7 +413,7 @@ static u32 msrs_to_save[] = {
>  #ifdef CONFIG_X86_64
>  	MSR_CSTAR, MSR_KERNEL_GS_BASE, MSR_SYSCALL_MASK, MSR_LSTAR,
>  #endif
> -	MSR_IA32_TIME_STAMP_COUNTER,
> +	MSR_IA32_TIME_STAMP_COUNTER, MSR_KVM_SYSTEM_TIME,
>   

Missing second MSR here.

>  
> +static void kvm_write_wall_clock(struct kvm_vcpu *v, gpa_t wall_clock)
> +{
> +	int version = 1;
> +	struct wall_clock wc;
> +	unsigned long flags;
> +	struct timespec wc_ts;
> +
> +	local_irq_save(flags);
> +	kvm_get_msr(v, MSR_IA32_TIME_STAMP_COUNTER,
> +			  &v->arch.hv_clock.tsc_timestamp);
> +	wc_ts = current_kernel_time();
> +	local_irq_restore(flags);
> +
> +	down_write(&current->mm->mmap_sem);
> +	kvm_write_guest(v->kvm, wall_clock, &version, sizeof(version));
> +	up_write(&current->mm->mmap_sem);
> +
> +	/* With all the info we got, fill in the values */
> +	wc.wc_sec = wc_ts.tv_sec;
> +	wc.wc_nsec = wc_ts.tv_nsec;
> +	wc.wc_version = ++version;
> +
> +	down_write(&current->mm->mmap_sem);
> +	kvm_write_guest(v->kvm, wall_clock, &wc, sizeof(wc));
> +	up_write(&current->mm->mmap_sem);
> +}
>   

missing blank line

> +static void kvm_write_guest_time(struct kvm_vcpu *v)
> +{
> +	struct timespec ts;
> +	unsigned long flags;
> +	struct kvm_vcpu_arch *vcpu = &v->arch;
> +	void *shared_kaddr;
> +
> +	if ((!vcpu->time_page))
> +		return;
> +
> +	/* Keep irq disabled to prevent changes to the clock */
> +	local_irq_save(flags);
> +	kvm_get_msr(v, MSR_IA32_TIME_STAMP_COUNTER,
> +			  &vcpu->hv_clock.tsc_timestamp);
> +	ktime_get_ts(&ts);
> +	local_irq_restore(flags);
> +
> +	/* With all the info we got, fill in the values */
> +
> +	vcpu->hv_clock.system_time = ts.tv_nsec +
> +				     (NSEC_PER_SEC * (u64)ts.tv_sec);
> +	/*
> +	 * The interface expects us to write an even number signaling that the
> +	 * update is finished. Since the guest won't see the intermediate states,
> +	 * we just write "2" at the end
> +	 */
> +	vcpu->hv_clock.version = 2;
> +
> +	preempt_disable();
>   

vcpu_load() is not preemptible anyway (and cannot be).

> +
> +	shared_kaddr = kmap_atomic(vcpu->time_page, KM_USER0);
> +
> +	memcpy(shared_kaddr + vcpu->time_offset, &vcpu->hv_clock,
> +		sizeof(vcpu->hv_clock));
> +
> +	kunmap_atomic(shared_kaddr, KM_USER0);
> +	preempt_enable();
> +
> +	mark_page_dirty(v->kvm, vcpu->time >> PAGE_SHIFT);
> +}
> +
>  
>  int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
>  {
> @@ -494,6 +562,25 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
>  	case MSR_IA32_MISC_ENABLE:
>  		vcpu->arch.ia32_misc_enable_msr = data;
>  		break;
> +	case MSR_KVM_WALL_CLOCK:
> +		vcpu->arch.wall_clock = data;
>   

This better be a global msr (in kvm->, not vcpu->).  There is precedent; 
some msrs in hyperthreading-capable processors are global to a core.

We need some notification to update wall clock as a result of 
time-of-day step changes, due to ntp or the user setting the date.  
Hopefully such a notifier exists.

-- 
error compiling committee.c: too many arguments to function


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