linux-kernel - Re: [PATCH 1/3] Introduce cpuid_on_cpu() and cpuid_eax_on

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:	Tue, 3 Apr 2007 15:42:50 +0200
From:	Andi Kleen <ak@...e.de>
To:	Alexey Dobriyan <adobriyan@...ru>
Cc:	akpm@...l.org, linux-kernel@...r.kernel.org, devel@...nvz.org,
	cpufreq@...ts.linux.org.uk, hpa@...or.com, davej@...emonkey.org.uk
Subject: Re: [PATCH 1/3] Introduce cpuid_on_cpu() and cpuid_eax_on_cpu()


> > Both powernow-k8 and cpuid attempt to schedule
> > to the target CPU so they should already run there. But it is some other CPU,
> > but when they ask your _on_cpu() functions they suddenly get a "real" CPU?
> > Where is the difference between these levels of virtualness?
> 
> *_on_cpu functions do some work on given physical CPU.
> set_cpus_allowed() in openvz operates on VCPU level, so process doing
> set_cpus_allowed() still could be scheduled anywhere. 

Ok so you have multple levels.

> > Also it has weird semantics. For example if you have multiple
> > virtual CPUs mapping to a single CPU then would the powernow-k8 driver
> > try to set the frequency multiple times on the same physical CPU?
> 
> If core cpufreq locking is OK, why would it?

It won't know about multiple CPUs mapping to a single CPU.
 
> apply_microcode() looks small enough to convert it to IPIs, but so far
> nobody asked for microcode updates in openvz.

Well if they try it they will probably have problems.
 
> > Before adding any hacks like this I think your vcpu concept
> > needs to be discussed properly on l-k. For me it doesn't look like it is
> > something good right now though.
> 
> Andi, I think it all relies on correctness of core cpufreq locking.

I have my doubts it will cope with you changing all reasonable expected semantics 
under it.

-Andi

-
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/