Re: [Xen-devel] [PATCH v2 2/2] x86: allow Meltdown band-aid to be disabled

[Juergen Gross <jgross@xxxxxxxx>]

On 16/01/18 13:12, George Dunlap wrote:
> On Mon, Jan 15, 2018 at 11:07 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>> First of all we don't need it on AMD systems. Additionally allow its use
>> to be controlled by command line option. For best backportability, this
>> intentionally doesn't use alternative instruction patching to achieve
>> the intended effect - while we likely want it, this will be later
>> follow-up.
> 
> Is it worth making it optional to apply to dom0?  In most cases, if an
> attacker can manage to get userspace on dom0, they should be able to
> take over the whole system anyway; turning it off on dom0 to get
> better performance seems like a policy decision that administrators
> might reasonably make.

You are implying here that Linux is insecure: why does userspace access
allow you to take over the machine? I can see that being true for root
access, but not for any other unprivileged user account.


Juergen

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