From: Andrew Cooper <andrew.cooper3@citrix.com>
To: <xen-devel@lists.xenproject.org>
Subject: Re: [Xen-devel] [PATCH 14/17] xen/arm64: head: Remove ID map as soon as it is not used
Date: Wed, 26 Jun 2019 21:44:09 +0100 [thread overview]
Message-ID: <86de69b7-b18c-1285-de94-89f18137ca0f@citrix.com> (raw)
In-Reply-To: <12426eb9-1545-b1f7-a85a-55c9e04b8cc4@arm.com>
On 26/06/2019 21:39, Julien Grall wrote:
> On 6/26/19 9:25 PM, Stefano Stabellini wrote:
>> On Mon, 10 Jun 2019, Julien Grall wrote:
>>> The ID map may clash with other parts of the Xen virtual memory layout.
>>> At the moment, Xen is handling the clash by only creating a mapping to
>>> the runtime virtual address before enabling the MMU.
>>>
>>> The rest of the mappings (such as the fixmap) will be mapped after the
>>> MMU is enabled. However, the code doing the mapping is not safe as it
>>> replace mapping without using the Break-Before-Make sequence.
>>>
>>> As the ID map can be anywhere in the memory, it is easier to remove all
>>> the entries added as soon as the ID map is not used rather than adding
>>> the Break-Before-Make sequence everywhere.
>>
>> I think it is a good idea, but I would ask you to mention 1:1 map
>> instead of "ID map" in comments and commit messages because that is the
>> wording we used in all comments so far (see the one in
>> create_page_tables and mm.c). It is easier to grep and refer to if we
>> use the same nomenclature. Note that I don't care about which
>> nomenclature we decide to use, I am only asking for consistency.
>> Otherwise, it would also work if you say it both way at least once:
>>
>> The ID map (1:1 map) may clash [...]
>
> I would rather drop the wording 1:1 as this is confusing. It is also
> not trivial to find anything on google typing "1:1".
"one-to-one mapping", or "identity map" are both common terminology.
1:1 is a common representation for the former, whereas ID is not a
abbreviation of "Identity".
If you don't want to use 1:1, then you need to say "The identity map" to
retain clarity.
~Andrew
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next prev parent reply other threads:[~2019-06-26 20:44 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-10 19:31 [Xen-devel] [PATCH 00/17] xen/arm64: Rework head.S to make it more compliant with the Arm Arm Julien Grall
2019-06-10 19:31 ` [Xen-devel] [PATCH 01/17] xen/arm64: head Mark the end of subroutines with ENDPROC Julien Grall
2019-06-25 23:23 ` Stefano Stabellini
2019-06-10 19:32 ` [Xen-devel] [PATCH 02/17] xen/arm64: head: Don't clobber x30/lr in the macro PRINT Julien Grall
2019-06-25 23:35 ` Stefano Stabellini
2019-06-25 23:59 ` Stefano Stabellini
2019-06-26 9:07 ` Julien Grall
2019-06-26 15:27 ` Stefano Stabellini
2019-06-26 15:28 ` Julien Grall
2019-06-26 18:32 ` Stefano Stabellini
2019-06-26 19:24 ` Julien Grall
2019-06-10 19:32 ` [Xen-devel] [PATCH 03/17] xen/arm64: head: Rework UART initialization on boot CPU Julien Grall
2019-06-25 23:49 ` Stefano Stabellini
2019-06-10 19:32 ` [Xen-devel] [PATCH 04/17] xen/arm64: head: Don't "reserve" x24 for the CPUID Julien Grall
2019-06-26 0:01 ` Stefano Stabellini
2019-06-26 9:09 ` Julien Grall
2019-06-10 19:32 ` [Xen-devel] [PATCH 05/17] xen/arm64: head: Introduce print_reg Julien Grall
2019-06-26 0:09 ` Stefano Stabellini
2019-06-26 9:10 ` Julien Grall
2019-07-15 18:46 ` Volodymyr Babchuk
2019-07-16 9:55 ` Julien Grall
2019-06-10 19:32 ` [Xen-devel] [PATCH 06/17] xen/arm64: head: Introduce distinct paths for the boot CPU and secondary CPUs Julien Grall
2019-06-26 1:00 ` Stefano Stabellini
2019-06-26 9:14 ` Julien Grall
2019-06-10 19:32 ` [Xen-devel] [PATCH 07/17] xen/arm64: head: Rework and document check_cpu_mode() Julien Grall
2019-06-26 1:00 ` Stefano Stabellini
2019-06-10 19:32 ` [Xen-devel] [PATCH 08/17] xen/arm64: head: Rework and document zero_bss() Julien Grall
2019-06-26 1:01 ` Stefano Stabellini
2019-06-26 9:16 ` Julien Grall
2019-06-10 19:32 ` [Xen-devel] [PATCH 09/17] xen/arm64: head: Improve coding style and document cpu_init() Julien Grall
2019-06-26 1:01 ` Stefano Stabellini
2019-06-26 10:34 ` Julien Grall
2019-06-10 19:32 ` [Xen-devel] [PATCH 10/17] xen/arm64: head: Improve coding style and document create_pages_tables() Julien Grall
2019-06-26 1:03 ` Stefano Stabellini
2019-06-26 11:20 ` Julien Grall
2019-06-10 19:32 ` [Xen-devel] [PATCH 11/17] xen/arm64: head: Document enable_mmu() Julien Grall
2019-06-26 1:03 ` Stefano Stabellini
2019-06-26 11:23 ` Julien Grall
2019-06-10 19:32 ` [Xen-devel] [PATCH 12/17] xen/arm64: head: Move assembly switch to the runtime PT in secondary CPUs path Julien Grall
2019-06-26 1:03 ` Stefano Stabellini
2019-06-10 19:32 ` [Xen-devel] [PATCH 13/17] xen/arm64: head: Don't setup the fixmap on secondary CPUs Julien Grall
2019-06-26 18:51 ` Stefano Stabellini
2019-06-26 19:26 ` Julien Grall
2019-06-10 19:32 ` [Xen-devel] [PATCH 14/17] xen/arm64: head: Remove ID map as soon as it is not used Julien Grall
2019-06-26 20:25 ` Stefano Stabellini
2019-06-26 20:39 ` Julien Grall
2019-06-26 20:44 ` Andrew Cooper [this message]
2019-06-28 0:36 ` Stefano Stabellini
2019-06-27 18:55 ` Stefano Stabellini
2019-06-27 19:30 ` Julien Grall
2019-07-10 19:39 ` Julien Grall
2019-07-30 17:33 ` Stefano Stabellini
2019-07-30 19:52 ` Julien Grall
2019-07-31 20:40 ` Stefano Stabellini
2019-07-31 21:07 ` Julien Grall
2019-06-10 19:32 ` [Xen-devel] [PATCH 15/17] xen/arm64: head: Rework and document setup_fixmap() Julien Grall
2019-06-26 19:01 ` Stefano Stabellini
2019-06-26 19:30 ` Julien Grall
2019-06-27 9:29 ` Julien Grall
2019-06-27 15:38 ` Stefano Stabellini
2019-06-26 19:02 ` Stefano Stabellini
2019-06-27 9:19 ` Julien Grall
2019-06-10 19:32 ` [Xen-devel] [PATCH 16/17] xen/arm64: head: Rework and document launch() Julien Grall
2019-06-26 19:12 ` Stefano Stabellini
2019-06-26 20:09 ` Julien Grall
2019-06-10 19:32 ` [Xen-devel] [PATCH 17/17] xen/arm64: Zero BSS after the MMU and D-cache is turned on Julien Grall
2019-06-26 19:29 ` Stefano Stabellini
2019-06-26 20:07 ` Julien Grall
2019-06-26 21:08 ` Stefano Stabellini
2019-06-27 11:04 ` Julien Grall
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