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Subject: Re: [PATCH 2/3] x86/mm: introduce __PAGE_KERNEL_GLOBAL
From:   Nadav Amit <nadav.amit@gmail.com>
In-Reply-To: <20180215132055.F341C31E@viggo.jf.intel.com>
Date:   Fri, 16 Feb 2018 09:47:49 -0800
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
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References: <20180215132053.6C9B48C8@viggo.jf.intel.com>
 <20180215132055.F341C31E@viggo.jf.intel.com>
To:     Dave Hansen <dave.hansen@linux.intel.com>
Sender: linux-kernel-owner@vger.kernel.org
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Dave Hansen <dave.hansen@linux.intel.com> wrote:

>=20
> From: Dave Hansen <dave.hansen@linux.intel.com>
>=20
> Kernel mappings are historically _PAGE_GLOBAL.  But, with PTI, we do =
not
> want them to be _PAGE_GLOBAL.  We currently accomplish this by simply
> clearing _PAGE_GLOBAL from the suppotred mask which ensures it is
> cleansed from many of our PTE construction sites:
>=20
>        if (!static_cpu_has(X86_FEATURE_PTI))
> 	                __supported_pte_mask |=3D _PAGE_GLOBAL;
>=20
> But, this also means that we now get *no* opportunity to use global
> pages with PTI, even for data which is shared such as the =
cpu_entry_area
> and entry/exit text.


Doesn=E2=80=99t this patch change the kernel behavior when the =
=E2=80=9Cnopti=E2=80=9D parameter is used?