From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Hugh Dickins <hughd@google.com>
Cc: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH mmotm/next] powerpc: fix powernv boot breakage on G5???
Date: Sun, 12 Jan 2014 23:34:08 +1100 [thread overview]
Message-ID: <1389530048.4672.104.camel@pasglop> (raw)
In-Reply-To: <alpine.LSU.2.11.1401120043210.1092@eggly.anvils>
On Sun, 2014-01-12 at 00:46 -0800, Hugh Dickins wrote:
> My PowerMac G5 cannot boot mmotm these days: different symptoms
> (starting /sbin/init failed? or ATA errors and hang?), with unrelated
> bugs adding to the confusion; but a bisection led to b5ff4211a829
> "powerpc/book3s: Queue up and process delayed MCE events". Since that
> series seems to be mostly about powernv, I tried changing BOOK3S_64
> to POWERNV in entry_64.S, which has got it back to working for me.
>
> Signed-off-by: Hugh Dickins <hughd@google.com>
> just in case this happens to be right, but it's well beyond me!
Mahesh, I think that code is broken. It calls into C code after R3 is
loaded which will clobber it, thus clobbering the return from syscalls.
Also, are you really adding that overhead to every syscall in the
system ? That doesn't sound great...
Why do you do something in syscall_exit to begin with anyway ? That
doesn't seen like a great way to process delayed mchecks... When do you
want to process them ? Any interruptible code ? Task level ?
The former, you might be better off just shooting something like a local
doorbell and use some IPI message bit or similar to indicate the
presence of a pending mcheck. The local doorbell will trigger whenever
interrupts are enabled.
Ben.
> ---
>
> arch/powerpc/kernel/entry_64.S | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- mmotm/arch/powerpc/kernel/entry_64.S 2014-01-10 18:24:56.940448828 -0800
> +++ linux/arch/powerpc/kernel/entry_64.S 2014-01-10 18:29:24.276455182 -0800
> @@ -184,7 +184,7 @@ syscall_exit:
> bl .do_show_syscall_exit
> ld r3,RESULT(r1)
> #endif
> -#ifdef CONFIG_PPC_BOOK3S_64
> +#ifdef CONFIG_PPC_POWERNV
> BEGIN_FTR_SECTION
> bl .machine_check_process_queued_event
> END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
next prev parent reply other threads:[~2014-01-12 12:34 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-12 8:46 [PATCH mmotm/next] powerpc: fix powernv boot breakage on G5??? Hugh Dickins
2014-01-12 12:34 ` Benjamin Herrenschmidt [this message]
2014-01-14 4:17 ` Benjamin Herrenschmidt
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=1389530048.4672.104.camel@pasglop \
--to=benh@kernel.crashing.org \
--cc=hughd@google.com \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=mahesh@linux.vnet.ibm.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).