From: Suzuki K Poulose <suzuki.poulose@arm.com>
To: Will Deacon <will@kernel.org>, Julien Grall <julien.grall@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, catalin.marinas@arm.com,
Dave.Martin@arm.com
Subject: Re: [PATCH] arm64: cpufeature: Don't expose ZFR0 to userspace when SVE is not enabled
Date: Mon, 14 Oct 2019 17:57:46 +0100 [thread overview]
Message-ID: <223c22d0-cfe3-4aed-6a8f-b80e44cb6548@arm.com> (raw)
In-Reply-To: <20191014164313.hu2dnf5rokntzhhp@willie-the-truck>
On 14/10/2019 17:43, Will Deacon wrote:
> On Mon, Oct 14, 2019 at 11:21:13AM +0100, Julien Grall wrote:
>> The kernel may not support SVE if CONFIG_ARM64_SVE is not set and
>> will hide the feature from the from userspace.
>
> I don't understand this sentence.
>
>> Unfortunately, the fields of ID_AA64ZFR0_EL1 are still exposed and could
>> lead to undefined behavior in userspace.
>
> Undefined in what way? Generally, we can't stop exposing things that
> we've exposed previously in case somebody has started relying on them, so
> this needs better justification.
We still expose them with this patch, but zero them out, if the SVE is not
supported. When SVE is enabled, we expose them as usual.
Cheers
Suzuki
next prev parent reply other threads:[~2019-10-14 16:57 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-14 10:21 Julien Grall
2019-10-14 14:41 ` Dave Martin
2019-10-14 15:30 ` Suzuki K Poulose
2019-10-14 15:32 ` Mark Rutland
2019-10-14 16:43 ` Will Deacon
2019-10-14 16:57 ` Suzuki K Poulose [this message]
2019-10-14 17:20 ` Will Deacon
2019-10-15 9:45 ` Dave Martin
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=223c22d0-cfe3-4aed-6a8f-b80e44cb6548@arm.com \
--to=suzuki.poulose@arm.com \
--cc=Dave.Martin@arm.com \
--cc=catalin.marinas@arm.com \
--cc=julien.grall@arm.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=will@kernel.org \
/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
all inboxes | Powered by JetHome®