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From: Avi Kivity <avi@qumranet.com>
To: Glauber de Oliveira Costa <gcosta@redhat.com>
Cc: "Dong, Eddie" <eddie.dong@intel.com>,
	linux-kernel@vger.kernel.org, jeremy@goop.org,
	hollisb@us.ibm.com, kvm-devel@lists.sourceforge.net
Subject: Re: [kvm-devel] [PATCH 2/3] kvmclock - the host part.
Date: Tue, 13 Nov 2007 16:47:50 +0200	[thread overview]
Message-ID: <4739B916.4000405@qumranet.com> (raw)
In-Reply-To: <4739906B.2080103@redhat.com>

Glauber de Oliveira Costa wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Dong, Eddie escreveu:
>   
>>> +static void kvm_write_guest_time(struct kvm_vcpu *vcpu) +{
>>> +	struct timespec ts;
>>> +	int r;
>>> +
>>> +	if (!vcpu->clock_gpa)
>>> +		return;
>>> +
>>> +	/* Updates version to the next odd number, indicating
>>> we're writing */
>>> +	vcpu->hv_clock.version++;
>>> +	kvm_write_guest(vcpu->kvm, vcpu->clock_gpa,
>>> &vcpu->hv_clock, PAGE_SIZE);
>>> +
>>> +	kvm_get_msr(vcpu, MSR_IA32_TIME_STAMP_COUNTER,
>>> +			  &vcpu->hv_clock.last_tsc);
>>> +
>>> +	ktime_get_ts(&ts);
>>>       
>> Do we need to disable preemption here?
>>     
> After thinking for a little while, you are theoretically right.
> In the current state, we could even be preempted between all operations
> ;-) Maybe after avi's suggestion of moving the call to it it will end up
> in a preempt safe region, but anyway, it's safer to add the preempt
> markers here.
> I'll put it in next version, thanks
>
>   

Well, you can't kvm_write_guest() with preemption enabled.

preempt notifiers to the rescue!  We have a callout during preemption, 
so you can just zero out a flag there, and when we're scheduled again 
retry the whole thing.

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


  parent reply	other threads:[~2007-11-13 14:49 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-11-08 22:39 [PATCH 0/3] Kvm clocksource, new spin Glauber de Oliveira Costa
2007-11-08 22:39 ` [PATCH 1/3] include files for kvmclock Glauber de Oliveira Costa
2007-11-08 22:39   ` [PATCH 2/3] kvmclock - the host part Glauber de Oliveira Costa
2007-11-08 22:39     ` [PATCH 3/3] kvmclock implementation, the guest part Glauber de Oliveira Costa
2007-11-11 10:17     ` [PATCH 2/3] kvmclock - the host part Avi Kivity
2007-11-13 11:28       ` Glauber de Oliveira Costa
2007-11-13 14:44         ` Avi Kivity
2007-11-13  5:00     ` [kvm-devel] " Dong, Eddie
2007-11-13 11:54       ` Glauber de Oliveira Costa
2007-11-13 12:08         ` Izik Eidus
2007-11-13 14:47         ` Avi Kivity [this message]
2007-11-13 15:23           ` Dong, Eddie
2007-11-13 16:12             ` Avi Kivity
2007-11-14  0:41               ` Dong, Eddie
2007-11-09  8:37   ` [PATCH 1/3] include files for kvmclock Gerd Hoffmann
2007-11-11  9:15     ` Avi Kivity

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