linux-kernel - Re: [PATCH v2 4/6] KVM-GST: KVM Steal time registration

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4D45649A.4090709@redhat.com>
Date:	Sun, 30 Jan 2011 15:16:10 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Glauber Costa <glommer@...hat.com>
CC:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	aliguori@...ibm.com, Rik van Riel <riel@...hat.com>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v2 4/6] KVM-GST: KVM Steal time registration

On 01/28/2011 09:52 PM, Glauber Costa wrote:
> Register steal time within KVM. Everytime we sample the steal time
> information, we update a local variable that tells what was the
> last time read. We then account the difference.
>
>
>
>   static void kvm_guest_cpu_offline(void *dummy)
>   {
>   	kvm_pv_disable_apf(NULL);
> +	native_write_msr(MSR_KVM_STEAL_TIME, 0, 0);
>   	apf_task_wake_all();
>   }

Don't use the native_ versions, they override the pvops implementation.  
It doesn't matter for kvm, but we're not supposed to know this.

> +	/*
> +	 * using nanoseconds introduces noise, which accumulates easily
> +	 * leading to big steal time values. We want, however, to keep the
> +	 * interface nanosecond-based for future-proofness. The hypervisor may
> +	 * adopt a similar strategy, but we can't rely on that.
> +	 */
> +	delta /= NSEC_PER_MSEC;
> +	delta *= NSEC_PER_MSEC;

You're working around this problem both in the guest and host.  So even 
if we fix it in one, it will still be broken in the other.

> +
> +	return delta;
> +}
> +

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

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/