linux-kernel - Re: [PATCH] x86/nospec: Unwreck the RSB stuffing

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Message-ID: <YvuVLUXjCBkLf8sJ@zn.tnic>
Date:   Tue, 16 Aug 2022 15:01:33 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Andrew Cooper <Andrew.Cooper3@...rix.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Daniel Sneddon <daniel.sneddon@...ux.intel.com>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "x86@...nel.org" <x86@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH] x86/nospec: Unwreck the RSB stuffing

On Tue, Aug 16, 2022 at 12:52:58PM +0000, Andrew Cooper wrote:
> One minor point.  Stuff 32 slots.
> 
> There are Intel parts out in the world with RSBs larger than 32 entries,
> and this loop does not fill the entire RSB on those.
> 
> This is why the 32-entry stuffing loop is explicitly not supported on
> eIBRS hardware as a general mechanism.

I'm guessing there will be an Intel patch forthcoming, making that
RSB_CLEAR_LOOPS more dynamic, based on the current model.

:-)

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette