From: Thomas Gleixner <tglx@linutronix.de>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>,
mingo@redhat.com, Borislav Petkov <bp@alien8.de>,
rkrcmar@redhat.com, x86@kernel.org, kvm@vger.kernel.org,
stable <stable@vger.kernel.org>, Jiri Kosina <jkosina@suse.cz>,
David Woodhouse <dwmw@amazon.co.uk>, Jon Masters <jcm@redhat.com>
Subject: Re: [PATCH 1/1] kvm/speculation: Allow KVM guests to use SSBD even if host does not
Date: Wed, 26 Jun 2019 16:23:57 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.21.1906261622570.32342@nanos.tec.linutronix.de> (raw)
In-Reply-To: <f258b10f-dae3-7cf4-5a0c-47fe067065b4@redhat.com>
On Wed, 26 Jun 2019, Paolo Bonzini wrote:
> On 26/06/19 14:41, Thomas Gleixner wrote:
> >> I think it's better to leave the guest in control of SSBD even if it's
> >> globally disabled. The harm cannot escape the guest and in particular
> >> it cannot escape to the sibling hyperthread.
> >
> > SSB allows guest to guest attacks IIRC
>
> SSB requires something like
>
> p = &foo;
> ...
> p = &bar;
> q = *p;
>
> where "p = &foo;" is executed from one privilege domain and the others
> are executed by another process or privilege domain. Unless two guests
> share memory, it is not possible to use it for guest-to-guest attacks.
Fair enough. It's way too hot to think clearly about these kind of problems
and there are simply way too many of them...
Thanks,
tglx
prev parent reply other threads:[~2019-06-26 14:24 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-10 17:20 [PATCH 1/1] kvm/speculation: Allow KVM guests to use SSBD even if host does not Alejandro Jimenez
2019-06-25 15:28 ` Mark Kanda
2019-06-25 15:45 ` Paolo Bonzini
2019-06-25 16:05 ` Thomas Gleixner
2019-06-25 17:58 ` Alejandro Jimenez
2019-06-25 18:22 ` Thomas Gleixner
2019-06-26 11:23 ` Paolo Bonzini
2019-06-26 12:41 ` Thomas Gleixner
2019-06-26 13:10 ` Paolo Bonzini
2019-06-26 14:23 ` Thomas Gleixner [this message]
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