linux-kernel - Re: [PATCH 0/4] Better memcpy

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Date:   Sat, 27 Aug 2016 09:28:34 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Tony Luck <tony.luck@...el.com>
Cc:     Boris Petkov <bp@...e.de>, Dan Williams <dan.j.williams@...el.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/4] Better memcpy_mcsafe()


* Tony Luck <tony.luck@...el.com> wrote:

> The original version of this used a check of the x86_model_id string
> for the magic "Intel(R) Xeon(R) CPU E7-" to determine whether we are
> running on a cpu that supports machine check recovery.
> 
> Boris tried to talk me out of that, but at the time I didn't think
> there was a viable alternate option, and somehow he fell for that line.
> 
> It turns out there is a better way, that isn't as painful as I thought
> it might be.  It does help guarantee future employment, as I'll
> have to add a new quirk for each CPU generation. But the check for "E7"
> would have eventually failed and required a patch too.
> 
> The downside of a quirk is that it runs after the X86_FEATURE patching
> code. So instead of "static_cpu_has()" we use "static_branch_unlikely(&mcsafe_key)"

So why not move it to the early PCI quirk code in arch/x86/ and get rid of this 
quirk within a quirk?

Thanks,

	Ingo