From: Dave Hansen <dave.hansen@linux.intel.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
"Andrea Arcangeli" <aarcange@redhat.com>,
"Andrew Lutomirski" <luto@kernel.org>,
"Kees Cook" <keescook@google.com>,
"Hugh Dickins" <hughd@google.com>,
"Jürgen Groß" <jgross@suse.com>,
"the arch/x86 maintainers" <x86@kernel.org>,
namit@vmware.com
Subject: Re: [PATCH 09/11] x86/pti: enable global pages for shared areas
Date: Mon, 2 Apr 2018 13:41:57 -0700 [thread overview]
Message-ID: <503339cf-7e54-0888-1767-c8ac87ce2130@linux.intel.com> (raw)
In-Reply-To: <CA+55aFx5GCahkr_-Y0qF5S=USCXhNcvWZ6gr_TxpvUVAh46STA@mail.gmail.com>
On 04/02/2018 10:56 AM, Linus Torvalds wrote:
> On Mon, Apr 2, 2018 at 10:27 AM, Dave Hansen
> <dave.hansen@linux.intel.com> wrote:
>> + /*
>> + * The cpu_entry_area is shared between the user and kernel
>> + * page tables. All of its ptes can safely be global.
>> + */
>> + if (boot_cpu_has(X86_FEATURE_PGE))
>> + pte = pte_set_flags(pte, _PAGE_GLOBAL);
> So this is where the quesion of "why is this conditional" is valid.
>
> We could set _PAGE_GLOBAL unconditionally, not bothering with testing
> X86_FEATURE_PGE.
I think we should just keep the check for now. Before this patch set,
on !X86_FEATURE_PGE systems, we cleared _PAGE_GLOBAL in virtually all
places due to masking via __supported_pte_mask.
It is rather harmless either way, but being _consistent_ (by keeping the
check) with all of our PTEs is nice.
next prev parent reply other threads:[~2018-04-02 20:41 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-02 17:27 [PATCH 00/11] [v3] Use global pages with PTI Dave Hansen
2018-04-02 17:27 ` [PATCH 01/11] x86/mm: factor out pageattr _PAGE_GLOBAL setting Dave Hansen
2018-04-02 17:52 ` Linus Torvalds
2018-04-02 20:23 ` Dave Hansen
2018-04-02 17:27 ` [PATCH 02/11] x86/mm: undo double _PAGE_PSE clearing Dave Hansen
2018-04-02 17:27 ` [PATCH 03/11] x86/mm: introduce "default" kernel PTE mask Dave Hansen
2018-04-02 17:27 ` [PATCH 04/11] x86/espfix: document use of _PAGE_GLOBAL Dave Hansen
2018-04-02 17:27 ` [PATCH 05/11] x86/mm: do not auto-massage page protections Dave Hansen
2018-04-02 17:27 ` [PATCH 06/11] x86/mm: remove extra filtering in pageattr code Dave Hansen
2018-04-02 17:27 ` [PATCH 07/11] x86/mm: comment _PAGE_GLOBAL mystery Dave Hansen
2018-04-02 17:27 ` [PATCH 08/11] x86/mm: do not forbid _PAGE_RW before init for __ro_after_init Dave Hansen
2018-04-02 17:27 ` [PATCH 09/11] x86/pti: enable global pages for shared areas Dave Hansen
2018-04-02 17:56 ` Linus Torvalds
2018-04-02 20:41 ` Dave Hansen [this message]
2018-04-02 17:27 ` [PATCH 10/11] x86/pti: never implicitly clear _PAGE_GLOBAL for kernel image Dave Hansen
2018-04-02 17:27 ` [PATCH 11/11] x86/pti: leave kernel text global for !PCID Dave Hansen
-- strict thread matches above, loose matches on Subject: below --
2018-04-06 20:55 [PATCH 00/11] [v5] Use global pages with PTI Dave Hansen
2018-04-06 20:55 ` [PATCH 09/11] x86/pti: enable global pages for shared areas Dave Hansen
2018-04-04 1:09 [PATCH 00/11] [v4] Use global pages with PTI Dave Hansen
2018-04-04 1:10 ` [PATCH 09/11] x86/pti: enable global pages for shared areas Dave Hansen
2018-04-04 4:45 ` Nadav Amit
2018-04-04 15:52 ` Dave Hansen
2018-04-04 16:09 ` Nadav Amit
2018-04-04 18:14 ` Thomas Gleixner
2018-03-23 17:44 [PATCH 00/11] Use global pages with PTI Dave Hansen
2018-03-23 17:45 ` [PATCH 09/11] x86/pti: enable global pages for shared areas Dave Hansen
2018-03-23 19:12 ` Nadav Amit
2018-03-23 19:36 ` Dave Hansen
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