From mboxrd@z Thu Jan  1 00:00:00 1970
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [RFC 05/10] x86/speculation: Add basic IBRS support
 infrastructure
Date: Mon, 22 Jan 2018 14:30:16 +0100
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Cc: Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        KarimAllah Ahmed <karahmed@amazon.de>,
        linux-kernel@vger.kernel.org, Andi Kleen <ak@linux.intel.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Andy Lutomirski <luto@kernel.org>,
        Arjan van de Ven <arjan@linux.intel.com>,
        Ashok Raj <ashok.raj@intel.com>,
        Asit Mallick <asit.k.mallick@intel.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Dave Hansen <dave.hansen@intel.com>,
        David Woodhouse <dwmw@amazon.co.uk>,
        "H . Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
        Janakarajan Natarajan <Janakarajan.Natarajan@amd.com>,
        Joerg Roedel <joro@8bytes.org>,
        Jun Nakajima <jun.nakajima@intel.com>,
        Laura Abbott <labbott@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
To: Borislav Petkov <bp@suse.de>
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On Mon, Jan 22, 2018 at 01:06:18PM +0100, Borislav Petkov wrote:
> On Mon, Jan 22, 2018 at 10:51:53AM +0100, Peter Zijlstra wrote:
> > That wouldn't be enough; AFAIU there's people with this stuff already
> > flashed in their BIOS. So the kernel needs to deal with it one way or
> > another.
> 
> Not a lot we can do there except maybe disable IBRS on those and users
> can go and complain to their BIOS vendor to give them a downgrade or
> they can downgrade themselves.
> 
> If we had free BIOS, this would've been a whole different story...

We kind of do, you can submit patches to UEFI, but I doubt that the
processor-specific portions are actually present in the Tianocore code
to be able to be patched.

What about LinuxBoot <https://linuxboot.org>, does it too take over too
late in the boot process to control this?

thanks,

greg k-h