From: Miles Chen <miles.chen@mediatek.com>
To: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Minchan Kim <minchan@kernel.org>,
<linux-arm-kernel@lists.infradead.org>,
<linux-kernel@vger.kernel.org>,
<linux-mediatek@lists.infradead.org>, <wsd_upstream@mediatek.com>,
Suren Baghdasaryan <surenb@google.com>
Subject: Re: [PATCH v2 4/4] arm: replace vector mem type with read-only type
Date: Tue, 27 Oct 2020 15:41:57 +0800 [thread overview]
Message-ID: <1603784517.12492.2.camel@mtkswgap22> (raw)
In-Reply-To: <20201023101257.GZ1551@shell.armlinux.org.uk>
On Fri, 2020-10-23 at 11:12 +0100, Russell King - ARM Linux admin wrote:
> On Fri, Oct 23, 2020 at 05:14:37PM +0800, Miles Chen wrote:
> > Since kernel no longer writes to the vector, try to replace
> > the vector mem type with read-only type and remove L_PTE_MT_VECTORS.
> >
> > from Catalin in [1]:
> > "
> > > I don't think this matters since the kernel no longer writes to the
> > > vectors page at run-time but it needs cleaning up a bit (and testing in
> > > case I missed something). IOW, do we still need a dedicated mapping type
> > > for the vectors or we can simply use the read-only user page attributes?
> > "
>
> Catalin is incorrect. If CONFIG_KUSER_HELPERS is enabled, then the
> vectors page is definitely written to - it's a user interface, so
> it's not going to change:
>
> #ifdef CONFIG_KUSER_HELPERS
> /*
> * User space must never try to access this
> * directly. Expect your app to break
> * eventually if you do so. The user helper
> * at 0xffff0fe0 must be used instead. (see
> * entry-armv.S for details)
> */
> *((unsigned int *)0xffff0ff0) = val;
> #endif
>
Thanks for the comment.
We have to keep L_PTE_MT_VECTORS for KUSER_HELPERS.
Miles
WARNING: multiple messages have this Message-ID (diff)
From: Miles Chen <miles.chen@mediatek.com>
To: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: wsd_upstream@mediatek.com,
Catalin Marinas <catalin.marinas@arm.com>,
linux-kernel@vger.kernel.org, Minchan Kim <minchan@kernel.org>,
linux-mediatek@lists.infradead.org,
Suren Baghdasaryan <surenb@google.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 4/4] arm: replace vector mem type with read-only type
Date: Tue, 27 Oct 2020 15:41:57 +0800 [thread overview]
Message-ID: <1603784517.12492.2.camel@mtkswgap22> (raw)
In-Reply-To: <20201023101257.GZ1551@shell.armlinux.org.uk>
On Fri, 2020-10-23 at 11:12 +0100, Russell King - ARM Linux admin wrote:
> On Fri, Oct 23, 2020 at 05:14:37PM +0800, Miles Chen wrote:
> > Since kernel no longer writes to the vector, try to replace
> > the vector mem type with read-only type and remove L_PTE_MT_VECTORS.
> >
> > from Catalin in [1]:
> > "
> > > I don't think this matters since the kernel no longer writes to the
> > > vectors page at run-time but it needs cleaning up a bit (and testing in
> > > case I missed something). IOW, do we still need a dedicated mapping type
> > > for the vectors or we can simply use the read-only user page attributes?
> > "
>
> Catalin is incorrect. If CONFIG_KUSER_HELPERS is enabled, then the
> vectors page is definitely written to - it's a user interface, so
> it's not going to change:
>
> #ifdef CONFIG_KUSER_HELPERS
> /*
> * User space must never try to access this
> * directly. Expect your app to break
> * eventually if you do so. The user helper
> * at 0xffff0fe0 must be used instead. (see
> * entry-armv.S for details)
> */
> *((unsigned int *)0xffff0ff0) = val;
> #endif
>
Thanks for the comment.
We have to keep L_PTE_MT_VECTORS for KUSER_HELPERS.
Miles
_______________________________________________
Linux-mediatek mailing list
Linux-mediatek@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-mediatek
WARNING: multiple messages have this Message-ID (diff)
From: Miles Chen <miles.chen@mediatek.com>
To: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: wsd_upstream@mediatek.com,
Catalin Marinas <catalin.marinas@arm.com>,
linux-kernel@vger.kernel.org, Minchan Kim <minchan@kernel.org>,
linux-mediatek@lists.infradead.org,
Suren Baghdasaryan <surenb@google.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 4/4] arm: replace vector mem type with read-only type
Date: Tue, 27 Oct 2020 15:41:57 +0800 [thread overview]
Message-ID: <1603784517.12492.2.camel@mtkswgap22> (raw)
In-Reply-To: <20201023101257.GZ1551@shell.armlinux.org.uk>
On Fri, 2020-10-23 at 11:12 +0100, Russell King - ARM Linux admin wrote:
> On Fri, Oct 23, 2020 at 05:14:37PM +0800, Miles Chen wrote:
> > Since kernel no longer writes to the vector, try to replace
> > the vector mem type with read-only type and remove L_PTE_MT_VECTORS.
> >
> > from Catalin in [1]:
> > "
> > > I don't think this matters since the kernel no longer writes to the
> > > vectors page at run-time but it needs cleaning up a bit (and testing in
> > > case I missed something). IOW, do we still need a dedicated mapping type
> > > for the vectors or we can simply use the read-only user page attributes?
> > "
>
> Catalin is incorrect. If CONFIG_KUSER_HELPERS is enabled, then the
> vectors page is definitely written to - it's a user interface, so
> it's not going to change:
>
> #ifdef CONFIG_KUSER_HELPERS
> /*
> * User space must never try to access this
> * directly. Expect your app to break
> * eventually if you do so. The user helper
> * at 0xffff0fe0 must be used instead. (see
> * entry-armv.S for details)
> */
> *((unsigned int *)0xffff0ff0) = val;
> #endif
>
Thanks for the comment.
We have to keep L_PTE_MT_VECTORS for KUSER_HELPERS.
Miles
_______________________________________________
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:[~2020-10-27 7:42 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-23 9:14 [PATCH v2 0/4] arm: support get_user_pages_fast Miles Chen
2020-10-23 9:14 ` Miles Chen
2020-10-23 9:14 ` Miles Chen
2020-10-23 9:14 ` [PATCH v2 1/4] arm: mm: use strict p[gum]d types Miles Chen
2020-10-23 9:14 ` Miles Chen
2020-10-23 9:14 ` Miles Chen
2020-10-23 9:14 ` [PATCH v2 2/4] arm: mm: reordering memory type table Miles Chen
2020-10-23 9:14 ` Miles Chen
2020-10-23 9:14 ` Miles Chen
2020-10-23 10:16 ` Russell King - ARM Linux admin
2020-10-23 10:16 ` Russell King - ARM Linux admin
2020-10-23 10:16 ` Russell King - ARM Linux admin
2020-10-27 8:03 ` Miles Chen
2020-10-27 8:03 ` Miles Chen
2020-10-27 8:03 ` Miles Chen
2020-10-23 9:14 ` [PATCH v2 3/4] arm: mm: introduce L_PTE_SPECIAL Miles Chen
2020-10-23 9:14 ` Miles Chen
2020-10-23 9:14 ` Miles Chen
2020-10-23 10:08 ` Russell King - ARM Linux admin
2020-10-23 10:08 ` Russell King - ARM Linux admin
2020-10-23 10:08 ` Russell King - ARM Linux admin
2020-10-27 7:45 ` Miles Chen
2020-10-27 7:45 ` Miles Chen
2020-10-27 7:45 ` Miles Chen
2020-10-27 9:11 ` Russell King - ARM Linux admin
2020-10-27 9:11 ` Russell King - ARM Linux admin
2020-10-27 9:11 ` Russell King - ARM Linux admin
2020-11-01 12:48 ` Miles Chen
2020-11-01 12:48 ` Miles Chen
2020-11-01 12:48 ` Miles Chen
2020-10-23 9:14 ` [PATCH v2 4/4] arm: replace vector mem type with read-only type Miles Chen
2020-10-23 9:14 ` Miles Chen
2020-10-23 9:14 ` Miles Chen
2020-10-23 10:12 ` Russell King - ARM Linux admin
2020-10-23 10:12 ` Russell King - ARM Linux admin
2020-10-23 10:12 ` Russell King - ARM Linux admin
2020-10-27 7:41 ` Miles Chen [this message]
2020-10-27 7:41 ` Miles Chen
2020-10-27 7:41 ` Miles Chen
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=1603784517.12492.2.camel@mtkswgap22 \
--to=miles.chen@mediatek.com \
--cc=catalin.marinas@arm.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mediatek@lists.infradead.org \
--cc=linux@armlinux.org.uk \
--cc=minchan@kernel.org \
--cc=surenb@google.com \
--cc=wsd_upstream@mediatek.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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.