From: Peter Collingbourne <pcc@google.com>
To: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Evgenii Stepanov <eugenis@google.com>,
Kostya Serebryany <kcc@google.com>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Dave Martin <Dave.Martin@arm.com>,
Szabolcs Nagy <szabolcs.nagy@arm.com>,
Florian Weimer <fw@deneb.enyo.de>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Kevin Brodsky <kevin.brodsky@arm.com>,
Andrey Konovalov <andreyknvl@google.com>,
Linux API <linux-api@vger.kernel.org>,
libc-alpha@sourceware.org
Subject: Re: [PATCH v6 1/3] arm64: mte: make the per-task SCTLR_EL1 field usable elsewhere
Date: Thu, 11 Feb 2021 20:47:33 -0800 [thread overview]
Message-ID: <CAMn1gO4PkzwY+pkLVR85Qp1VUYybZ9dMG-E_f1SP3cOE4FOfqQ@mail.gmail.com> (raw)
In-Reply-To: <20210126124958.GC29702@willie-the-truck>
On Tue, Jan 26, 2021 at 4:50 AM Will Deacon <will@kernel.org> wrote:
>
> On Tue, Dec 29, 2020 at 10:59:13PM -0800, Peter Collingbourne wrote:
> > In an upcoming change we are going to introduce per-task SCTLR_EL1
> > bits for PAC. Move the existing per-task SCTLR_EL1 field out of the
> > MTE-specific code so that we will be able to use it from both the
> > PAC and MTE code paths and make the task switching code more efficient.
> >
> > Signed-off-by: Peter Collingbourne <pcc@google.com>
> > Link: https://linux-review.googlesource.com/id/Ic65fac78a7926168fa68f9e8da591c9e04ff7278
> > ---
> > arch/arm64/Kconfig | 4 +++
> > arch/arm64/include/asm/mte.h | 4 ---
> > arch/arm64/include/asm/processor.h | 10 ++++++-
> > arch/arm64/kernel/mte.c | 47 ++++++------------------------
> > arch/arm64/kernel/process.c | 34 +++++++++++++++++----
> > 5 files changed, 50 insertions(+), 49 deletions(-)
> >
> > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> > index 05e17351e4f3..82e38d1ca012 100644
> > --- a/arch/arm64/Kconfig
> > +++ b/arch/arm64/Kconfig
> > @@ -348,6 +348,9 @@ config KASAN_SHADOW_OFFSET
> > default 0xeffffff800000000 if ARM64_VA_BITS_36 && KASAN_SW_TAGS
> > default 0xffffffffffffffff
> >
> > +config ARM64_NEED_SCTLR_USER
> > + bool
> > +
> > source "arch/arm64/Kconfig.platforms"
> >
> > menu "Kernel Features"
> > @@ -1653,6 +1656,7 @@ config ARM64_MTE
> > # Required for tag checking in the uaccess routines
> > depends on ARM64_PAN
> > select ARCH_USES_HIGH_VMA_FLAGS
> > + select ARM64_NEED_SCTLR_USER
>
> I'm not sure I'd bother with this; is it the end of the world if we do this
> unconditionally?
I think I'd be fine with doing it unconditionally. If both PAC and MTE
are disabled then I believe that the only additional code that we
would end up executing is the comparison between prev and next
sctlr_user on task switch in process.c (which would always yield
false) and since task switch is much less common than entry/exit it
seems acceptable to me.
Peter
prev parent reply other threads:[~2021-02-12 4:47 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-30 6:59 Peter Collingbourne
2020-12-30 6:59 ` [PATCH v6 2/3] arm64: Introduce prctl(PR_PAC_{SET,GET}_ENABLED_KEYS) Peter Collingbourne
2021-01-26 12:49 ` Will Deacon
2021-02-12 4:52 ` [PATCH v6 2/3] arm64: Introduce prctl(PR_PAC_{SET, GET}_ENABLED_KEYS) Peter Collingbourne
2020-12-30 6:59 ` [PATCH v6 3/3] arm64: pac: Optimize kernel entry/exit key installation code paths Peter Collingbourne
2021-01-26 13:09 ` Will Deacon
2021-02-12 5:01 ` Peter Collingbourne
2021-02-12 11:01 ` James Morse
2021-02-12 18:20 ` Peter Collingbourne
2021-01-26 12:49 ` [PATCH v6 1/3] arm64: mte: make the per-task SCTLR_EL1 field usable elsewhere Will Deacon
2021-02-12 4:47 ` Peter Collingbourne [this message]
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=CAMn1gO4PkzwY+pkLVR85Qp1VUYybZ9dMG-E_f1SP3cOE4FOfqQ@mail.gmail.com \
--to=pcc@google.com \
--cc=Dave.Martin@arm.com \
--cc=andreyknvl@google.com \
--cc=catalin.marinas@arm.com \
--cc=eugenis@google.com \
--cc=fw@deneb.enyo.de \
--cc=kcc@google.com \
--cc=kevin.brodsky@arm.com \
--cc=libc-alpha@sourceware.org \
--cc=linux-api@vger.kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=szabolcs.nagy@arm.com \
--cc=vincenzo.frascino@arm.com \
--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;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).