linux-kernel - Re: [PATCH 01/17] x86: spec_ctrl: fix SPEC

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Message-ID: <c56d8911-5323-ac40-97b3-fa8920725197@redhat.com>
Date:   Mon, 23 Sep 2019 12:22:23 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Andrea Arcangeli <aarcange@...hat.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        "Dr. David Alan Gilbert" <dgilbert@...hat.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Peter Xu <peterx@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/17] x86: spec_ctrl: fix SPEC_CTRL initialization after
 kexec

On 20/09/19 23:24, Andrea Arcangeli wrote:
> We can't assume the SPEC_CTRL msr is zero at boot because it could be
> left enabled by a previous kernel booted with
> spec_store_bypass_disable=on.
> 
> Without this fix a boot with spec_store_bypass_disable=on followed by
> a kexec boot with spec_store_bypass_disable=off would erroneously and
> unexpectedly leave bit 2 set in SPEC_CTRL.
> 
> Signed-off-by: Andrea Arcangeli <aarcange@...hat.com>

Can you send this out separately, so that Thomas et al. can pick it up
as a bug fix?

Thanks,

Paolo