From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Subject: Re: [RFC,05/10] x86/speculation: Add basic IBRS support
 infrastructure
Date: Wed, 31 Jan 2018 14:04:49 +0000
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Cc: Thomas Gleixner <tglx@linutronix.de>,
        Christophe de Dinechin <christophe.de.dinechin@gmail.com>,
        Alan Cox <gnomes@lxorguk.ukuu.org.uk>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        David Woodhouse <dwmw2@infradead.org>,
        Arjan van de Ven <arjan@linux.intel.com>,
        Eduardo Habkost <ehabkost@redhat.com>,
        KarimAllah Ahmed <karahmed@amazon.de>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Andi Kleen <ak@linux.intel.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Andy Lutomirski <luto@kernel.org>,
        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>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "H . Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mi
To: Borislav Petkov <bp@suse.de>
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* Borislav Petkov (bp@suse.de) wrote:
> On Wed, Jan 31, 2018 at 12:30:36PM +0000, Dr. David Alan Gilbert wrote:
> > Indeed, it's only for this weird case where you suddenly need to change
> > it.
> 
> No, there's more:
> 
> 	.name = "Broadwell-noTSX",
> 	.name = "Haswell-noTSX",

Haswell came out and we made the CPU definition, and then got a
microcode update that removed the feature.

So the common feature of noTSX and IBRS is that they're the only two
cases where a CPU has released and then the flags have changed later.

Dave

> -- 
> Regards/Gruss,
>     Boris.
> 
> SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
> -- 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK