From: Anton Blanchard <anton@samba.org>
To: benh@kernel.crashing.org, paulus@samba.org,
michael@ellerman.id.au, scottwood@freescale.com
Cc: linuxppc-dev@lists.ozlabs.org
Subject: [PATCH] powerpc: Clear RI and EE at the same time in system call exit
Date: Wed, 30 May 2012 08:22:00 +1000 [thread overview]
Message-ID: <20120530082200.67fe1328@kryten> (raw)
In-Reply-To: <4FC5104E.1000504@freescale.com>
Hi Scott,
> > syscall_exit_work:
> > + mtmsrd r10,1 /* Restore RI */
>
> That mtmsrd needs an #ifdef CONFIG_PPC_BOOK3S
Thanks!
Anton
--
In system call exit we currently clear RI and EE separately. An
mtmsrd is a slow operation and we can save cycles by doing it all
in one go.
This does complicate things a bit - we have to be careful to restore
RI if we branch out before returning to userspace.
On a POWER7 with virtual cputime disabled this patch improves the
null system call by 7%.
Signed-off-by: Anton Blanchard <anton@samba.org>
---
Index: linux-build/arch/powerpc/kernel/entry_64.S
===================================================================
--- linux-build.orig/arch/powerpc/kernel/entry_64.S 2012-05-29 21:22:40.293549055 +1000
+++ linux-build/arch/powerpc/kernel/entry_64.S 2012-05-30 07:47:31.380737406 +1000
@@ -197,7 +197,16 @@ syscall_exit:
wrteei 0
#else
ld r10,PACAKMSR(r13)
- mtmsrd r10,1
+ /*
+ * For performance reasons we clear RI the same time that we
+ * clear EE. We only need to clear RI just before we restore r13
+ * below, but batching it with EE saves us one expensive mtmsrd call.
+ * We have to be careful to restore RI if we branch anywhere from
+ * here (eg syscall_exit_work).
+ */
+ li r9,MSR_RI
+ andc r11,r10,r9
+ mtmsrd r11,1
#endif /* CONFIG_PPC_BOOK3E */
ld r9,TI_FLAGS(r12)
@@ -214,17 +223,6 @@ BEGIN_FTR_SECTION
END_FTR_SECTION_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
andi. r6,r8,MSR_PR
ld r4,_LINK(r1)
- /*
- * Clear RI before restoring r13. If we are returning to
- * userspace and we take an exception after restoring r13,
- * we end up corrupting the userspace r13 value.
- */
-#ifdef CONFIG_PPC_BOOK3S
- /* No MSR:RI on BookE */
- li r12,MSR_RI
- andc r11,r10,r12
- mtmsrd r11,1 /* clear MSR.RI */
-#endif /* CONFIG_PPC_BOOK3S */
beq- 1f
ACCOUNT_CPU_USER_EXIT(r11, r12)
@@ -271,6 +269,9 @@ syscall_enosys:
b syscall_exit
syscall_exit_work:
+#ifdef CONFIG_PPC_BOOK3S
+ mtmsrd r10,1 /* Restore RI */
+#endif
/* If TIF_RESTOREALL is set, don't scribble on either r3 or ccr.
If TIF_NOERROR is set, just save r3 as it is. */
prev parent reply other threads:[~2012-05-29 22:22 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-29 11:20 [PATCH] powerpc: Clear RI and EE at the same time in system call exit Anton Blanchard
2012-05-29 18:07 ` Scott Wood
2012-05-29 22:22 ` Anton Blanchard [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=20120530082200.67fe1328@kryten \
--to=anton@samba.org \
--cc=benh@kernel.crashing.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=michael@ellerman.id.au \
--cc=paulus@samba.org \
--cc=scottwood@freescale.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).