linux-kernel - Re: [PATCH 3/7] KVM-HV: KVM Steal time implementation

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]

Date:	Sun, 19 Jun 2011 15:59:56 +0300
From:	Gleb Natapov <gleb@...hat.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	Glauber Costa <glommer@...hat.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Rik van Riel <riel@...hat.com>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Anthony Liguori <aliguori@...ibm.com>,
	Eric B Munson <emunson@...bm.net>
Subject: Re: [PATCH 3/7] KVM-HV: KVM Steal time implementation

On Sun, Jun 19, 2011 at 03:35:58PM +0300, Avi Kivity wrote:
> On 06/15/2011 12:09 PM, Gleb Natapov wrote:
> >>
> >>  Actually, I'd expect most read/writes to benefit from caching, no?
> >>  So why don't we just rename kvm_write_guest_cached() to
> >>  kvm_write_guest(), and the few places - if any - that need to force
> >>  transversing of the gfn mappings, get renamed to
> >>  kvm_write_guest_uncached ?
> >>
> >Good idea. I do not see any places where kvm_write_guest_uncached is
> >needed from a brief look. Avi?
> >
> 
> kvm_write_guest_cached() needs something to supply the cache, and
> needs recurring writes to the same location.  Neither of these are
> common (for example, instruction emulation doesn't have either).
> 
Correct. Missed that. So what about changing steal time to use
kvm_write_guest_cached()?

> >>
> >>  If done like you said, time spent on the hypervisor is accounted as
> >>  steal time. I don't think it is.
> >I thought that this is the point of a steal time. Running other
> >tasks/guests is a hypervisor overhead too after all :) Also what about
> >time spend serving host interrupts between put/get? It will not be
> >accounted as steal time, correct?
> 
> With accurate interrupt time accounting, it should be.  Otherwise
> general hypervisor overhead is not steal time.
> 
> (i.e. if the host is not overcommitted, steal time should be close to zero).
> 

--
			Gleb.
--
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/