All of lore.kernel.org
 help / color / mirror / Atom feed
From: Arnd Bergmann <arnd@kernel.org>
To: Helge Deller <deller@gmx.de>
Cc: Parisc List <linux-parisc@vger.kernel.org>,
	James Bottomley <James.Bottomley@hansenpartnership.com>,
	John David Anglin <dave.anglin@bell.net>
Subject: Re: [PATCH v2] parisc: Fix boot with kernel v5.14
Date: Thu, 2 Sep 2021 18:35:32 +0000	[thread overview]
Message-ID: <CAK8P3a0zwnEUK_ztPRBx0H9VGBoPVY-+aASFV97zSKrL=diXUA@mail.gmail.com> (raw)
In-Reply-To: <YTDaZAMvAipdvkaB@ls3530>

On Thu, Sep 2, 2021 at 2:06 PM Helge Deller <deller@gmx.de> wrote:
>
> Kernel v5.14 has various changes to optimize unaligned memory accesses,
> e.g. commit 0652035a5794 ("asm-generic: unaligned: remove byteshift helpers").
>
> Those changes break the bootloader and other places in kernel for parisc
> which needs byte-wise accesses to unaligned memory.
>
> Here is an updated patch/hack which fixes those boot problems by adding
> a compiler optimization barrier. More info and background can be found in BZ:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102162
>
> Signed-off-by: Helge Deller <deller@gmx.de>

Right, this should fix it, but I tend to agree with what Andrew Pinski
said: the existing version is actually correct and allows valid
optimizations on static variables as long as those are correctly
annotated in C. The problem on parisc seems to be that at least
one variable is generated by the linker in a way that is incompatible
with the psABI but declared as a regular __u32.

       Arnd

  reply	other threads:[~2021-09-02 18:35 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-31 20:46 [PATCH] parisc: Fix boot with kernel v5.14 Helge Deller
2021-09-02 14:06 ` [PATCH v2] " Helge Deller
2021-09-02 18:35   ` Arnd Bergmann [this message]
2021-09-02 19:48     ` Helge Deller
2021-09-02 20:19       ` Helge Deller
2021-09-02 20:41       ` Arnd Bergmann
2021-09-05 21:40         ` Helge Deller
2021-09-06 10:54           ` Arnd Bergmann
2021-09-06 20:15             ` Helge Deller
2021-09-06 21:49               ` Arnd Bergmann

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='CAK8P3a0zwnEUK_ztPRBx0H9VGBoPVY-+aASFV97zSKrL=diXUA@mail.gmail.com' \
    --to=arnd@kernel.org \
    --cc=James.Bottomley@hansenpartnership.com \
    --cc=dave.anglin@bell.net \
    --cc=deller@gmx.de \
    --cc=linux-parisc@vger.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 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.