linux-kernel - [RFC PATCH 01/14] sparc64: placeholder for needed mmu shared context patching

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Date:   Fri, 16 Dec 2016 10:35:24 -0800
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     sparclinux@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     "David S . Miller" <davem@...emloft.net>,
        Bob Picco <bob.picco@...cle.com>,
        Nitin Gupta <nitin.m.gupta@...cle.com>,
        Vijay Kumar <vijay.ac.kumar@...cle.com>,
        Julian Calaby <julian.calaby@...il.com>,
        Adam Buchbinder <adam.buchbinder@...il.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>
Subject: [RFC PATCH 01/14] sparc64: placeholder for needed mmu shared context patching

MMU shared context patching will be supported on Sun4V platforms with
Niagara 2 or later processors.  There will be a need for kernel patching
based on this criteria.  This 'patch' simply adds a comment as a reminder
and placeholder to add that support.

For now, MMU shared context support will be determined at follows:
- sun4v patching will be used for shared context support.  This is too
  general as most but not all sun4v platforms contain the required
  processors.
- A new config option (CONFIG_SHARED_MMU_CTX) is added

Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
---
 arch/sparc/kernel/setup_64.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/sparc/kernel/setup_64.c b/arch/sparc/kernel/setup_64.c
index 6b7331d..ffda69b 100644
--- a/arch/sparc/kernel/setup_64.c
+++ b/arch/sparc/kernel/setup_64.c
@@ -276,6 +276,17 @@ void sun_m7_patch_2insn_range(struct sun4v_2insn_patch_entry *start,
 	}
 }
 
+/*
+ * FIXME - TODO
+ *
+ * Shared MMU context support will only be provided on sun4v platforms
+ * with Niagara 2 or later processors.  A patching mechanism for this
+ * this type of support will need to be implemented.  For now, the code
+ * is making the too general assumption of supporting shared context on
+ * all sun4v platforms.  This is a placeholder to add correct support
+ * at a later time.
+ */
+
 static void __init sun4v_patch(void)
 {
 	extern void sun4v_hvapi_init(void);
-- 
2.7.4