From: Suzuki.Poulose@arm•com (Suzuki K. Poulose)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCHv3 03/11] arm64: Introduce helpers for page table levels
Date: Thu, 15 Oct 2015 14:48:47 +0100 [thread overview]
Message-ID: <561FAEBF.2090508@arm.com> (raw)
In-Reply-To: <20151015133001.GF21930@cbox>
On 15/10/15 14:30, Christoffer Dall wrote:
> On Thu, Oct 15, 2015 at 02:14:22PM +0100, Suzuki K. Poulose wrote:
>> On 15/10/15 13:44, Mark Rutland wrote:
>>> On Thu, Oct 15, 2015 at 01:37:35PM +0200, Christoffer Dall wrote:
>>>> On Wed, Oct 14, 2015 at 12:20:26PM +0100, Suzuki K. Poulose wrote:
>> * The maximum number of levels supported by the architecture is 4. Hence at starting
>> * at level n, we hanve (4 - n) levels of translation. So, the total number of bits
>
> nit: s/hanve/have/
Fixed.
>
>> * mapped by an entry at level n is :
>> *
>> * ((4 - n) - 1) * (PAGE_SHIFT - 3) + PAGE_SHIFT
>> *
>> * Rearranging it a bit we get :
>> * (4 - n) * (PAGE_SHIFT - 3) + 3
>> */
>>
>> Or we could use the formula without rearranging.
>>
> Either way, even I get it now.
>
> Thanks for the explanation!!
:). I was involved too much in these calculations that, the formula looked
obvious to me, when I wrote it. But yes, I did realise that it is indeed
complicated, once I really started looking at explaining why I wrote it so.
Thanks for being patient :) and complaining peacefully !
Btw, I have a revised (hopefully better) version here :
/*
* Size mapped by an entry at level n ( 0 <= n <= 3)
* We map (PAGE_SHIFT - 3) at all translation levels and PAGE_SHIFT bits
* in the final page. The maximum number of translation levels supported by
* the architecture is 4. Hence, starting at at level n, we have further
* ((4 - n) - 1) levels of translation excluding the offset within the page.
* So, the total number of bits mapped by an entry@level n is :
*
* ((4 - n) - 1) * (PAGE_SHIFT - 3) + PAGE_SHIFT
*
* Rearranging it a bit we get :
* (4 - n) * (PAGE_SHIFT - 3) + 3
*/
>
> Assuming some version of this goes in:
>
> Acked-by: Christoffer Dall <christoffer.dall@linaro•org>
>
Thanks. I lost two interview questions though ;)
Suzuki
next prev parent reply other threads:[~2015-10-15 13:48 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-14 11:20 [PATCHv3 00/11] arm64: 16K translation granule support Suzuki K. Poulose
2015-10-14 11:20 ` [PATCHv3 01/11] arm64: Move swapper pagetable definitions Suzuki K. Poulose
2015-10-14 11:42 ` Mark Rutland
2015-10-14 12:41 ` Suzuki K. Poulose
2015-10-14 11:20 ` [PATCHv3 02/11] arm64: Handle section maps for swapper/idmap Suzuki K. Poulose
2015-10-14 12:06 ` Mark Rutland
2015-10-14 13:21 ` Suzuki K. Poulose
2015-10-14 14:51 ` Mark Rutland
2015-10-14 15:08 ` Suzuki K. Poulose
2015-10-14 15:14 ` Mark Rutland
2015-10-14 11:20 ` [PATCHv3 03/11] arm64: Introduce helpers for page table levels Suzuki K. Poulose
2015-10-14 17:07 ` Mark Rutland
2015-10-15 9:35 ` Suzuki K. Poulose
2015-10-15 10:37 ` Mark Rutland
2015-10-15 11:40 ` Christoffer Dall
2015-10-15 11:37 ` Christoffer Dall
2015-10-15 12:44 ` Mark Rutland
2015-10-15 13:14 ` Suzuki K. Poulose
2015-10-15 13:30 ` Christoffer Dall
2015-10-15 13:48 ` Suzuki K. Poulose [this message]
2015-10-15 14:15 ` Christoffer Dall
2015-10-14 11:20 ` [PATCHv3 04/11] arm64: Calculate size for idmap_pg_dir at compile time Suzuki K. Poulose
2015-10-14 17:12 ` Mark Rutland
2015-10-14 11:20 ` [PATCHv3 05/11] arm64: Handle 4 level page table for swapper Suzuki K. Poulose
2015-10-14 17:15 ` Mark Rutland
2015-10-14 11:20 ` [PATCHv3 06/11] arm64: Clean config usages for page size Suzuki K. Poulose
2015-10-14 11:20 ` [PATCHv3 07/11] arm64: Kconfig: Fix help text about AArch32 support with 64K pages Suzuki K. Poulose
2015-10-14 17:16 ` Mark Rutland
2015-10-14 11:20 ` [PATCHv3 08/11] arm64: Check for selected granule support Suzuki K. Poulose
2015-10-14 17:24 ` Mark Rutland
2015-10-14 17:32 ` Mark Rutland
2015-10-15 9:45 ` Suzuki K. Poulose
2015-10-15 10:39 ` Mark Rutland
2015-10-14 21:13 ` Jeremy Linton
2015-10-15 9:48 ` Suzuki K. Poulose
2015-10-15 10:45 ` Mark Rutland
2015-10-15 11:25 ` Suzuki K. Poulose
2015-10-15 12:37 ` Mark Rutland
2015-10-15 12:58 ` Suzuki K. Poulose
2015-10-16 8:03 ` Ard Biesheuvel
2015-10-15 14:47 ` Jeremy Linton
2015-10-15 15:02 ` Suzuki K. Poulose
2015-10-15 15:11 ` Mark Rutland
2015-10-16 8:11 ` Ard Biesheuvel
2015-10-14 11:20 ` [PATCHv3 09/11] arm64: Add page size to the kernel image header Suzuki K. Poulose
2015-10-14 17:27 ` Mark Rutland
2015-10-15 9:19 ` Suzuki K. Poulose
2015-10-14 11:20 ` [PATCHv3 10/11] arm64: Add 16K page size support Suzuki K. Poulose
2015-10-14 15:40 ` Jeremy Linton
2015-10-14 15:53 ` Suzuki K. Poulose
2015-10-15 14:06 ` Mark Rutland
2015-10-15 14:48 ` Suzuki K. Poulose
2015-10-15 15:36 ` Steve Capper
2015-10-15 15:48 ` Suzuki K. Poulose
2015-10-14 11:20 ` [PATCHv3 11/11] arm64: 36 bit VA Suzuki K. Poulose
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=561FAEBF.2090508@arm.com \
--to=suzuki.poulose@arm$(echo .)com \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox