From: Dave Hansen <dave.hansen@linux.intel.com>
To: Nadav Amit <nadav.amit@gmail.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
luto@kernel.org, torvalds@linux-foundation.org,
keescook@google.com, hughd@google.com, jgross@suse.com,
x86@kernel.org
Subject: Re: [PATCH 2/3] x86/mm: introduce __PAGE_KERNEL_GLOBAL
Date: Fri, 16 Feb 2018 11:06:30 -0800 [thread overview]
Message-ID: <0f8abc68-1092-1bae-d244-1adbbee455f9@linux.intel.com> (raw)
In-Reply-To: <DF43D1DD-42EE-4545-9F54-4BC2395D66EA@gmail.com>
On 02/16/2018 10:25 AM, Nadav Amit wrote:
>> +#ifdef CONFIG_PAGE_TABLE_ISOLATION
>> +#define __PAGE_KERNEL_GLOBAL 0
>> +#else
>> +#define __PAGE_KERNEL_GLOBAL _PAGE_GLOBAL
>> +#endif
> ...
>> --- a/arch/x86/mm/pageattr.c~kpti-no-global-for-kernel-mappings 2018-02-13 15:17:56.148210060 -0800
>> +++ b/arch/x86/mm/pageattr.c 2018-02-13 15:17:56.153210060 -0800
>> @@ -593,7 +593,8 @@ try_preserve_large_page(pte_t *kpte, uns
>> * different bit positions in the two formats.
>> */
>> req_prot = pgprot_4k_2_large(req_prot);
>> - req_prot = pgprot_set_on_present(req_prot, _PAGE_GLOBAL | _PAGE_PSE);
>> + req_prot = pgprot_set_on_present(req_prot,
>> + __PAGE_KERNEL_GLOBAL | _PAGE_PSE);
>> req_prot = canon_pgprot(req_prot);
> From these chunks, it seems to me as req_prot will not have the global bit
> on when a??noptia?? parameter is provided. What am I missing?
That's a good point. The current patch does not allow the use of
_PAGE_GLOBAL via _PAGE_KERNEL_GLOBAL when CONFIG_PAGE_TABLE_ISOLATION=y,
but booted with nopti. It's a simple enough fix. Logically:
#ifdef CONFIG_PAGE_TABLE_ISOLATION
#define __PAGE_KERNEL_GLOBAL static_cpu_has(X86_FEATURE_PTI) ?
0 : _PAGE_GLOBAL
#else
#define __PAGE_KERNEL_GLOBAL _PAGE_GLOBAL
#endif
But I don't really want to hide that gunk in a macro like that. It
might make more sense as a static inline. I'll give that a shot and resent.
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next prev parent reply other threads:[~2018-02-16 19:06 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-15 13:20 [PATCH 0/3] Use global pages with PTI Dave Hansen
2018-02-15 13:20 ` [PATCH 1/3] x86/mm: factor out conditional pageattr PTE bit setting code Dave Hansen
2018-02-15 13:20 ` [PATCH 2/3] x86/mm: introduce __PAGE_KERNEL_GLOBAL Dave Hansen
2018-02-16 17:47 ` Nadav Amit
2018-02-16 18:03 ` Dave Hansen
2018-02-16 18:25 ` Nadav Amit
2018-02-16 19:06 ` Dave Hansen [this message]
2018-02-16 19:54 ` Nadav Amit
2018-02-16 20:00 ` Dave Hansen
2018-02-16 23:19 ` Dave Hansen
2018-02-15 13:20 ` [PATCH 3/3] x86/pti: enable global pages for shared areas Dave Hansen
2018-02-15 17:47 ` [PATCH 0/3] Use global pages with PTI Linus Torvalds
2018-02-15 18:13 ` Dave Hansen
2018-02-15 23:55 ` Dave Hansen
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