From: Dave Martin <Dave.Martin@arm.com>
To: Mark Brown <broonie@kernel.org>
Cc: Julien Grall <julien@xen.com>, Julien Grall <julien@xen.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Zhang Lei <zhang.lei@jp.fujitsu.com>,
Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org,
Daniel Kiss <Daniel.Kiss@arm.com>
Subject: Re: [PATCH v7 1/2] arm64/sve: Split TIF_SVE into separate execute and register state flags
Date: Mon, 1 Feb 2021 15:35:53 +0000 [thread overview]
Message-ID: <20210201153550.GE13952@arm.com> (raw)
In-Reply-To: <20210201122901.11331-2-broonie@kernel.org>
On Mon, Feb 01, 2021 at 12:29:00PM +0000, Mark Brown wrote:
> Currently we have a single flag TIF_SVE which says that a task is
> allowed to execute SVE instructions without trapping and also that full
> SVE register state is stored for the task. This results in us doing
> extra work storing and restoring the full SVE register state even in
> those cases where the ABI is that only the first 128 bits of the Z0-V31
> registers which are shared with the FPSIMD V0-V31 are valid.
>
> In order to allow us to avoid these overheads split TIF_SVE up so that
> we have two separate flags, TIF_SVE_EXEC which allows execution of SVE
> instructions without trapping and TIF_SVE_FULL_REGS which indicates that
> the full SVE register state is stored. If both are set the behaviour is
> as currently, if TIF_SVE_EXEC is set without TIF_SVE_FULL_REGS then we
> save and restore only the FPSIMD registers until we return to userspace
> with TIF_SVE_EXEC enabled at which point we convert the FPSIMD registers
> to SVE. It is not meaningful to have TIF_SVE_FULL_REGS set without
> TIF_SVE_EXEC.
>
> This patch is intended only to split the flags, it does not take
> avantage of the ability to set the flags independently and the new
> state with TIF_SVE_EXEC only should not be observed.
>
> This is based on earlier work by Julien Gral implementing a slightly
> different approach.
>
> Signed-off-by: Mark Brown <broonie@kernel.org>
While I'm trying to get my head around this, can you sketch out the
mapping between the old flag combinations (including Julien's
TIF_SVE_NEEDS_FLUSH) and yours?
[...]
Cheers
---Dave
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-02-01 15:37 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-01 12:28 [PATCH v7 0/2] arm64/sve: Improve performance when handling SVE access traps Mark Brown
2021-02-01 12:29 ` [PATCH v7 1/2] arm64/sve: Split TIF_SVE into separate execute and register state flags Mark Brown
2021-02-01 15:35 ` Dave Martin [this message]
2021-02-01 15:45 ` Mark Brown
2021-02-09 17:59 ` Dave Martin
2021-02-09 22:16 ` Mark Brown
2021-02-10 19:52 ` Mark Brown
2021-02-10 10:56 ` Dave Martin
2021-02-10 14:54 ` Mark Brown
2021-02-10 15:42 ` Dave Martin
2021-02-10 17:14 ` Mark Brown
2021-02-10 18:15 ` Dave Martin
2021-02-01 12:29 ` [PATCH v7 2/2] arm64/sve: Rework SVE trap access to minimise memory access Mark Brown
2021-02-10 11:09 ` Dave Martin
2021-02-10 17:54 ` Mark Brown
2021-02-08 17:26 ` [PATCH v7 0/2] arm64/sve: Improve performance when handling SVE access traps Dave Martin
2021-02-09 18:22 ` Mark Brown
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=20210201153550.GE13952@arm.com \
--to=dave.martin@arm.com \
--cc=Daniel.Kiss@arm.com \
--cc=broonie@kernel.org \
--cc=catalin.marinas@arm.com \
--cc=julien@xen.com \
--cc=julien@xen.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=will@kernel.org \
--cc=zhang.lei@jp.fujitsu.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
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;
as well as URLs for NNTP newsgroup(s).