From: Oliver Upton <oliver.upton@linux.dev>
To: Fuad Tabba <tabba@google.com>
Cc: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
maz@kernel.org, will@kernel.org, qperret@google.com,
seanjc@google.com, alexandru.elisei@arm.com,
catalin.marinas@arm.com, philmd@linaro.org, james.morse@arm.com,
suzuki.poulose@arm.com, mark.rutland@arm.com, broonie@kernel.org,
joey.gouly@arm.com, rananta@google.com, yuzenghui@huawei.com
Subject: Re: [PATCH v3 11/11] KVM: arm64: Drop sve_cond_update_zcr_vq_*
Date: Thu, 30 May 2024 11:22:42 -0700 [thread overview]
Message-ID: <ZljD8pu5Z5ujHny2@linux.dev> (raw)
In-Reply-To: <20240528125914.277057-12-tabba@google.com>
Hi,
On Tue, May 28, 2024 at 01:59:14PM +0100, Fuad Tabba wrote:
> The conditional update likely doesn't help performance, but makes
> the code a bit more difficult to read. Remove these macros and
> just write directly to ZCR.
>
> Signed-off-by: Fuad Tabba <tabba@google.com>
> ---
> This patch is meant as an RFC, and undoes the previous patch.
> Please feel free to accept/drop whichever patches you think make
> sense.
The motivation behind this helper is to avoid unnecessary synchronizing
behavior, since as you note the architecture does not require
explicit synchronization for the value to become visible to subsequent
instructions.
Now, that doesn't _necessarily_ imply full blown context synchronization,
but it isn't too far fetched to think a conservative implementation does
exactly that upon ZCR write.
--
Thanks,
Oliver
_______________________________________________
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:[~2024-05-30 18:23 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-28 12:59 [PATCH v3 00/11] KVM: arm64: Fix handling of host fpsimd/sve state in protected mode Fuad Tabba
2024-05-28 12:59 ` [PATCH v3 01/11] KVM: arm64: Reintroduce __sve_save_state Fuad Tabba
2024-05-31 12:26 ` Mark Brown
2024-06-03 8:28 ` Fuad Tabba
2024-05-28 12:59 ` [PATCH v3 02/11] KVM: arm64: Abstract set/clear of CPTR_EL2 bits behind helper Fuad Tabba
2024-05-28 12:59 ` [PATCH v3 03/11] KVM: arm64: Specialize handling of host fpsimd state on trap Fuad Tabba
2024-05-31 13:35 ` Mark Brown
2024-05-28 12:59 ` [PATCH v3 04/11] KVM: arm64: Allocate memory mapped at hyp for host sve state in pKVM Fuad Tabba
2024-05-28 12:59 ` [PATCH v3 05/11] KVM: arm64: Eagerly restore host fpsimd/sve " Fuad Tabba
2024-05-31 14:09 ` Mark Brown
2024-06-03 8:37 ` Fuad Tabba
2024-06-03 13:27 ` Mark Brown
2024-06-03 13:48 ` Marc Zyngier
2024-06-03 14:15 ` Mark Brown
2024-06-03 14:31 ` Marc Zyngier
2024-05-28 12:59 ` [PATCH v3 06/11] KVM: arm64: Consolidate initializing the host data's fpsimd_state/sve " Fuad Tabba
2024-05-28 12:59 ` [PATCH v3 07/11] KVM: arm64: Refactor CPACR trap bit setting/clearing to use ELx format Fuad Tabba
2024-05-28 12:59 ` [PATCH v3 08/11] KVM: arm64: Add an isb before restoring guest sve state Fuad Tabba
2024-05-28 12:59 ` [PATCH v3 09/11] KVM: arm64: Do not use sve_cond_update_zcr updating with ZCR_ELx_LEN_MASK Fuad Tabba
2024-05-28 12:59 ` [PATCH v3 10/11] KVM: arm64: Do not perform an isb() if ZCR_EL2 isn't updated Fuad Tabba
2024-05-28 12:59 ` [PATCH v3 11/11] KVM: arm64: Drop sve_cond_update_zcr_vq_* Fuad Tabba
2024-05-30 18:22 ` Oliver Upton [this message]
2024-05-30 20:14 ` Oliver Upton
2024-05-31 6:40 ` Fuad Tabba
2024-05-28 13:13 ` [PATCH v3 00/11] KVM: arm64: Fix handling of host fpsimd/sve state in protected mode Fuad Tabba
2024-05-30 18:29 ` Oliver Upton
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=ZljD8pu5Z5ujHny2@linux.dev \
--to=oliver.upton@linux.dev \
--cc=alexandru.elisei@arm.com \
--cc=broonie@kernel.org \
--cc=catalin.marinas@arm.com \
--cc=james.morse@arm.com \
--cc=joey.gouly@arm.com \
--cc=kvmarm@lists.linux.dev \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=mark.rutland@arm.com \
--cc=maz@kernel.org \
--cc=philmd@linaro.org \
--cc=qperret@google.com \
--cc=rananta@google.com \
--cc=seanjc@google.com \
--cc=suzuki.poulose@arm.com \
--cc=tabba@google.com \
--cc=will@kernel.org \
--cc=yuzenghui@huawei.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).