linux-kernel - Re: [RFC PATCH 00/16] x86/split_lock: Enable #AC exception for split locked accesses

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Message-ID: <20180529174047.GC212416@romley-ivt3.sc.intel.com>
Date:   Tue, 29 May 2018 10:40:48 -0700
From:   Fenghua Yu <fenghua.yu@...el.com>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...e.hu>,
        "H. Peter Anvin" <hpa@...ux.intel.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Rafael Wysocki <rafael.j.wysocki@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Alan Cox <alan@...ux.intel.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        Arjan van de Ven <arjan@...radead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [RFC PATCH 00/16] x86/split_lock: Enable #AC exception for split
 locked accesses

On Tue, May 29, 2018 at 10:28:11AM -0700, Dave Hansen wrote:
> On 05/29/2018 10:25 AM, Fenghua Yu wrote:
> > (By the way, ISE and SDM don't mention other important details, e.g. 
> > the fact that operand is fetched to cache before split lock is
> > checked. Without the fact, it's hard to explain that only split lock
> > generates bus lock in chapter 8.1.4 in SDM vol3.)
> 
> That's a bummer.  You're working with the folks that own those documents
> to get that fixed up, right?

Yes, I already asked them to add some missing parts in future ISE and SDM.

> 
> > Maybe I can add "Current TEST_CTL implementation is per-core. The patches
> > are supposed to work even when TEST_CTL is per-thread (or even per-
> > socket) in future as well."?
> 
> Yes, that would be a very important part of the software implementation
> to mention.

I'll do that in the next version.

Thanks.

-Fenghua