linux-kernel - Re: [PATCH] KVM: SVM: fix trashing of MSR_TSC

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:	Thu, 7 Jul 2016 14:47:12 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	Eduardo Habkost <ehabkost@...hat.com>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH] KVM: SVM: fix trashing of MSR_TSC_AUX

On Thu, Jul 07, 2016 at 02:28:29PM +0200, Paolo Bonzini wrote:
> Because otherwise you couldn't do live migration from new QEMU + new
> kernel to new QEMU + old kernel.  QEMU tries to avoid requiring lockstep
> upgrades of QEMU and KVM (unlike for example perf).

Hmm, ok.

About that - and I've asked about it a couple of times already - how
would you guys feel about a testing feature to qemu - something I'd love
to have with which I can set arbitrary CPUID bits for testing kernels?

I.e., something like that:

qemu ... -cpu=Opteron_G5,cpuid_leaf=<bla>,eax=<..>,ebx=<...>, ...,filter=off

The filter=off thing is to disable the checking in
x86_cpu_filter_features() so that those arbitrary CPUID leafs are
actually simulated to the guest.

Would something like that make sense for upstream or should I hack it in
locally only?

Because it sure does help a lot when testing kernel features for
unreleased CPUs but for which the code is already being submitted. And
with a qemu feature like that, we could at least smoke-test those a bit.

Hmmm?

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.