linux-kernel - Re: [PATCH v2] sparc64: Add support for Application Data Integrity (ADI)

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Message-ID: <56DE0AC3.9070503@oracle.com>
Date:	Mon, 7 Mar 2016 15:12:03 -0800
From:	Rob Gardner <rob.gardner@...cle.com>
To:	Khalid Aziz <khalid.aziz@...cle.com>,
	David Miller <davem@...emloft.net>
Cc:	corbet@....net, akpm@...ux-foundation.org,
	dingel@...ux.vnet.ibm.com, bob.picco@...cle.com,
	kirill.shutemov@...ux.intel.com, aneesh.kumar@...ux.vnet.ibm.com,
	aarcange@...hat.com, arnd@...db.de, sparclinux@...r.kernel.org,
	mhocko@...e.cz, chris.hyser@...cle.com, richard@....at,
	vbabka@...e.cz, koct9i@...il.com, oleg@...hat.com,
	gthelen@...gle.com, jack@...e.cz, xiexiuqi@...wei.com,
	Vineet.Gupta1@...opsys.com, luto@...nel.org, ebiederm@...ssion.com,
	bsegall@...gle.com, geert@...ux-m68k.org, dave@...olabs.net,
	adobriyan@...il.com, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-arch@...r.kernel.org, linux-api@...r.kernel.org
Subject: Re: [PATCH v2] sparc64: Add support for Application Data Integrity
 (ADI)

On 03/07/2016 01:33 PM, Khalid Aziz wrote:
>
> That is a possibility but limited in scope. An address range covered 
> by a single TTE can have large number of tags. Version tags are set on 
> cacheline. In extreme case, one could set a tag for each set of 
> 64-bytes in a page. Also tags are set completely in userspace and no 
> transition occurs to kernel space, so kernel has no idea of what tags 
> have been set.

   ...
> I have not found a way to query the MMU on tags.
>

To query the tag for a cache line, you just read it back with ldxa and 
ASI_MCD_PRIMARY (ie, asi 0x90), basically the same way you stored the 
tag in the first place.

Rob