linux-kernel - Re: [RFC 00/13] x86/mm: PCID and INVPCID

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Message-ID: <CA+55aFxmc83LRHRSAsnydpqy4Y-K2V9RvRCU+dhV-kWzu2Gvpg@mail.gmail.com>
Date:	Fri, 8 Jan 2016 15:42:32 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Andy Lutomirski <luto@...nel.org>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Borislav Petkov <bp@...en8.de>,
	Brian Gerst <brgerst@...il.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Oleg Nesterov <oleg@...hat.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [RFC 00/13] x86/mm: PCID and INVPCID

On Fri, Jan 8, 2016 at 3:36 PM, Andy Lutomirski <luto@...capital.net> wrote:
>>
>> Either things have changed (newer hardware with more pcids perhaps?)
>> or you did a better job at it.
>
> On my Skylake laptop, all of the PCID bits appear to have at least
> some effect.  Whether this means it gets hashed or whether this means
> that all of the bits are real, I don't know.

They have always gotten hashed, and no the bits aren't real - hardware
doesn't actually have as many bits in the pcid as there are in cr3.

              Linus