linux-kernel - Re: [PATCH 05/16] KVM-HDR: Implement wallclock over KVM

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 for Android: free password hash cracker in your pocket

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

Date:	Wed, 26 Jan 2011 17:17:02 +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
Subject: Re: [PATCH 05/16] KVM-HDR: Implement wallclock over KVM - KVM Virtual
 Memory

On 01/26/2011 02:20 PM, Glauber Costa wrote:
> On Wed, 2011-01-26 at 13:13 +0200, Avi Kivity wrote:
> >  On 01/24/2011 08:06 PM, Glauber Costa wrote:
> >  >  As a proof of concept to KVM - Kernel Virtual Memory, this patch
> >  >  implements wallclock grabbing on top of it. At first, it may seem
> >  >  as a waste of work to just redo it, since it is working well. But over the
> >  >  time, other MSRs were added - think ASYNC_PF - and more will probably come.
> >  >  After this patch, we won't need to ever add another virtual MSR to KVM.
> >  >
> >
> >  So instead of adding MSRs, we're adding area identifiers.  What did we gain?
>
> * No risk of namespace clashes of any kind,
> * less need for userspace coordination for feature enablement,

That's a bug, not a feature.

> * more robust mechanism that can do discovery even on early boot,

cpuid/wrmsr should be robust enough.

> * more informative result values can be passed on to guest kernel,

True.

> * more flexibility, since we go back to userspace if we can't handle
> some request. Also, some requests are better handled by userspace
> anyway. But again, maybe this is a separate issue here...

Yes.

> * size information goes together with base, allowing for extending
> structures (well, maybe I should add versioning explicitly?)
>

We could do that as well with wrmsr, by having the size as the first 
field of the structure.  Usually the size isn't really interesting, 
though, since you need to discover/enable the new features independently.

-- 
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/