linux-kernel - Re: [kvm-devel] [PATCH 2/3] kvmclock

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Message-ID: <4739906B.2080103@redhat.com>
Date:	Tue, 13 Nov 2007 09:54:19 -0200
From:	Glauber de Oliveira Costa <gcosta@...hat.com>
To:	"Dong, Eddie" <eddie.dong@...el.com>
CC:	linux-kernel@...r.kernel.org, jeremy@...p.org, hollisb@...ibm.com,
	kvm-devel@...ts.sourceforge.net, avi@...ranet.com
Subject: Re: [kvm-devel] [PATCH 2/3] kvmclock - the host part.

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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

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