linux-kernel - [PATCH] x86/mm: Enable 5-level paging support by default

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Message-Id: <20190913095452.40592-1-kirill.shutemov@linux.intel.com>
Date:   Fri, 13 Sep 2019 12:54:52 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH] x86/mm: Enable 5-level paging support by default

Support of boot-time switching between 4- and 5-level paging mode is
upstream since 4.17.

We run internal testing with 5-level paging support enabled for a while
and it doesn't not cause any functional or performance regression on
4-level paging hardware.

The only 5-level paging related regressions I saw were in early boot
code that runs independently from CONFIG_X86_5LEVEL.

The next major release of distributions expected to have
CONFIG_X86_5LEVEL=y.

Enable the option by default. It may help to catch obscure bugs early.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 arch/x86/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 222855cc0158..2f7cb91d850e 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1483,6 +1483,7 @@ config X86_PAE

 config X86_5LEVEL
 	bool "Enable 5-level page tables support"
+	default y
 	select DYNAMIC_MEMORY_LAYOUT
 	select SPARSEMEM_VMEMMAP
 	depends on X86_64
-- 
2.21.0