linux-kernel - Re: [tip:efi/core] x86/mm/pat: Use _PAGE_GLOBAL bit for EFI page table mappings

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Message-ID: <CA+55aFwR332=Ng1K_MKQ7n-xqttdwTc8RQbq_6jNBpPBU_0ykw@mail.gmail.com>
Date:	Wed, 24 Feb 2016 10:56:13 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Borislav Petkov <bp@...en8.de>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>,
	"Ravi V. Shankar" <ravi.v.shankar@...el.com>,
	Toshi Kani <toshi.kani@...com>,
	Brian Gerst <brgerst@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Luis Rodriguez <mcgrof@...e.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>, ricardo.neri@...el.com,
	Hugh Dickins <hughd@...gle.com>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: Re: [tip:efi/core] x86/mm/pat: Use _PAGE_GLOBAL bit for EFI page
 table mappings

On Wed, Feb 24, 2016 at 8:36 AM, Andy Lutomirski <luto@...capital.net> wrote:
>>
>> So the EFI runtime crap should not change once it is mapped. And those
>> should be global. It is only natural.
>
> Why is it natural?
>
> Long-term, I'd rather see EFI runtime services use an actual mm_struct
> and use_mm.

Definitely.

The EFI runtime page mapping may be unchanging, but that doesn't mean
we should be mapping it all the time - the mapping may not change, but
we will change away from it.

So marking those pages global is very wrong.

                 Linus