linux-kernel - Re: Can't boot as Xen dom0 due to commit fe055896

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Date:   Thu, 15 Dec 2016 18:36:09 +0100
From:   Borislav Petkov <bp@...e.de>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc:     Juergen Gross <jgross@...e.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        xen-devel <xen-devel@...ts.xenproject.org>
Subject: Re: Can't boot as Xen dom0 due to commit fe055896

On Thu, Dec 15, 2016 at 12:27:49PM -0500, Boris Ostrovsky wrote:
> It will probably fix it but I don't think we want this: it's a
> build-time solution. Most kernels have XEN on even though they are
> booted bare-metal.

Lemme tell you want I want: a way to detect I'm running on xen. Does
CPUID(4) work really early, at load_ucode_bsp() time?

IOW, can I use some of the functionality hypervisor_cpuid_base() uses to
detect xen and stop loading any further?

> I meant, for example:
> 
>         proc_fam = find_cpu_family_by_equiv_cpu(proc_id);
>         if (!proc_fam) {
>                 pr_err("No patch family for equiv ID: 0x%04x\n", proc_id);
>                 return crnt_size;
>         }
> 
> -boris
> 
> > It returns
> > crnt_size which can be a positive number so that we can advance to the
> > next patch in the blob.
^^^^^^^^^^^^^^^

Read what I wrote here.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--