linux-kernel - Re: [PATCH v2] MIPS64: Support of at least 48 bits of SEGBITS

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 15 May 2015 14:01:52 -0700
From:	Leonid Yegoshin <Leonid.Yegoshin@...tec.com>
To:	David Daney <ddaney.cavm@...il.com>
CC:	<aleksey.makarov@...iga.com>, <james.hogan@...tec.com>,
	<paul.burton@...tec.com>, <david.daney@...ium.com>,
	<peterz@...radead.org>, <linux-mips@...ux-mips.org>,
	<linux-kernel@...r.kernel.org>, <ralf@...ux-mips.org>,
	<davidlohr@...com>, <kirill@...temov.name>,
	<akpm@...ux-foundation.org>, <mingo@...nel.org>
Subject: Re: [PATCH v2] MIPS64: Support of at least 48 bits of SEGBITS

On 05/15/2015 01:49 PM, David Daney wrote:
> On 05/14/2015 06:34 PM, Leonid Yegoshin wrote:
>> SEGBITS default is 40 bits or less, depending from CPU type.
>> This patch introduces 48bits of application virtual address (SEGBITS) 
>> support.
>> It is defined only for 16K and 64K pages and is optional (configurable).
>>
>> Penalty - a small number of additional pages for generic (small) 
>> applications.
>> But for 64K pages it adds 3rd level of PTE structure, which has a little
>> impact during software TLB refill.
>>
>> This patch is needed because MIPS I6XXX and P6XXX cores have 48 bit of
>> virtual address in each segment (SEGBITS).
>>
>
> Those processors don't require the patch.  You wrote the patch to give 
> a larger VA space at the request of kernel users.  So perhaps say:
>
>   The patch (optionally) increases the VA space available to userspace 
> processes from N-bits to 48-bits
>

... if CPU model supports that

>
>>
>> +config 48VMBITS
>
> Should probabaly be called VABITS instead of VMBITS to match the terms 
> used in the architecture reference manuals, as well as other ports 
> (ARM64).
>
> Perhaps MIPS_VA_BITS_48

I don't mind here. It can be even called 48SEGBITS or so, to match arch 
manual more. MIPS Arch manual never says about VA bits but speaks about 
PABITS and SEGBITS.

- Leonid.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/