linux-kernel - Re: [PATCH v4 7/7] x86/speculation: Add basic IBPB (Indirect Branch Prediction Barrier) support

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Message-ID: <20180125115016.ov72ajqb6z7scdrc@pd.tnic>
Date:   Thu, 25 Jan 2018 12:50:16 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     David Woodhouse <dwmw2@...radead.org>
Cc:     arjan@...ux.intel.com, tglx@...utronix.de, karahmed@...zon.de,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        tim.c.chen@...ux.intel.com, peterz@...radead.org,
        pbonzini@...hat.com, ak@...ux.intel.com,
        torvalds@...ux-foundation.org, gregkh@...ux-foundation.org,
        dave.hansen@...el.com, gnomes@...rguk.ukuu.org.uk,
        ashok.raj@...el.com, mingo@...nel.org
Subject: Re: [PATCH v4 7/7] x86/speculation: Add basic IBPB (Indirect Branch
 Prediction Barrier) support

On Thu, Jan 25, 2018 at 11:47:35AM +0000, David Woodhouse wrote:
> I did already do the explicit clobbers now you reminded me how to do
> them, but I elected not to use ASM_NO_INPUT_CLOBBER() because on
> balance, losing the MSR_IA32_PRED_CMD / PRED_CMD_IBPB definitions and
> having to hard-code the numbers was not so much of a win.

and I'm thinking exactly the opposite: if an alternative can lose a
bunch of inputs which don't change, then that's a good thing.

-- 
Regards/Gruss,
    Boris.

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