linux-kernel - Re: [RFC PATCH 05/14] sparc64: Add PAGE_SHR

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Message-Id: <20161217.221255.1870405962737594028.davem@davemloft.net>
Date:   Sat, 17 Dec 2016 22:12:55 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     mike.kravetz@...cle.com
Cc:     sparclinux@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, bob.picco@...cle.com,
        nitin.m.gupta@...cle.com, vijay.ac.kumar@...cle.com,
        julian.calaby@...il.com, adam.buchbinder@...il.com,
        kirill.shutemov@...ux.intel.com, mhocko@...e.com,
        akpm@...ux-foundation.org
Subject: Re: [RFC PATCH 05/14] sparc64: Add PAGE_SHR_CTX flag

From: Mike Kravetz <mike.kravetz@...cle.com>
Date: Fri, 16 Dec 2016 10:35:28 -0800

> @@ -166,6 +166,7 @@ bool kern_addr_valid(unsigned long addr);
>  #define _PAGE_EXEC_4V	  _AC(0x0000000000000080,UL) /* Executable Page      */
>  #define _PAGE_W_4V	  _AC(0x0000000000000040,UL) /* Writable             */
>  #define _PAGE_SOFT_4V	  _AC(0x0000000000000030,UL) /* Software bits        */
> +#define _PAGE_SHR_CTX_4V  _AC(0x0000000000000020,UL) /* Shared Context       */
>  #define _PAGE_PRESENT_4V  _AC(0x0000000000000010,UL) /* Present              */
>  #define _PAGE_RESV_4V	  _AC(0x0000000000000008,UL) /* Reserved             */
>  #define _PAGE_SZ16GB_4V	  _AC(0x0000000000000007,UL) /* 16GB Page            */

You really don't need this.

The VMA is available, and you can obtain the information you need
about whether this is a shared mapping or not from the. It just isn't
being passed down into things like set_huge_pte_at().  Simply make it
do so.