linux-kernel - Re: [PATCH v2 3/4] arch/x86: Optionally flush L1D on context switch

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Message-ID: <8be4a3c08fce8c47f7d7e42c6d5b6c854a39995c.camel@kernel.crashing.org>
Date:   Wed, 08 Apr 2020 09:37:04 +1000
From:   Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:     Kees Cook <keescook@...omium.org>, Balbir Singh <sblbir@...zon.com>
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org,
        jpoimboe@...hat.com, tony.luck@...el.com, x86@...nel.org,
        dave.hansen@...el.com
Subject: Re: [PATCH v2 3/4] arch/x86: Optionally flush L1D on context switch

On Tue, 2020-04-07 at 11:26 -0700, Kees Cook wrote:
> > Add arch specific prctl()'s to opt-in to the L1D cache on context
> > switch
> > out, the existing mechanisms of tracking prev_mm via cpu_tlbstate
> > is
> > reused. cond_ibpb() is refactored and renamed into
> > cond_mitigation().
> 
> I still think this should be a generic prctl(). If there is a strong
> reason not to do this, can it be described in the commit log here?

Agreed.

Cheers,
Ben.