linux-kernel - Re: [RFC 09/13] x86/mm: Disable interrupts when flushing the TLB using CR3

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Date:	Wed, 13 Jan 2016 15:32:56 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>, X86 ML <x86@...nel.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Borislav Petkov <bp@...en8.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Brian Gerst <brgerst@...il.com>
Subject: Re: [RFC 09/13] x86/mm: Disable interrupts when flushing the TLB
 using CR3

On Mon, Jan 11, 2016 at 2:51 AM, Ingo Molnar <mingo@...nel.org> wrote:
>
> * Linus Torvalds <torvalds@...ux-foundation.org> wrote:
>
>> >> Or is there some reason you wanted the odd flags version? If so, that
>> >> should be documented.
>> >
>> > What do you mean "odd"?
>>
>> It's odd because it makes no sense for non-pcid (christ, I wish Intel had just
>> called it "asid" instead, "pcid" always makes me react to "pci"), and I think it
>> would make more sense to pair up the pcid case with the invpcid rather than have
>> those preemption rules here.
>
> The naming is really painful, so a trivial suggestion: could we just name all the
> Linux side bits 'asid' or 'ctx_id' (even in x86 arch code) and only use 'PCID'
> nomenclature in the very lowest level code?

I'd be okay with "pctx_id" or "pctxid" for this, I think.  I'd like to
at least make it somewhat obvious how it maps back to hardware.

FWIW, I'd guess that Intel deviated from convention because their
actual address space id is (vpid, pcid), and calling it (vpid, asid)
might have been slightly confusing.  Or not.

--Andy