linux-kernel - Re: [PATCH v6 14/19] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it

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Message-ID: <7159845.QvBivUPZSS@wuerfel>
Date:	Wed, 02 Dec 2015 14:54:18 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org, will.deacon@....com
Cc:	Yury Norov <ynorov@...iumnetworks.com>, pinskia@...il.com,
	Prasun.Kapoor@...iumnetworks.com, catalin.marinas@....com,
	Nathan_Lynch@...tor.com, linux-kernel@...r.kernel.org,
	agraf@...e.de, klimov.linux@...il.com, broonie@...nel.org,
	jan.dakinevich@...il.com, joseph@...esourcery.com,
	ddaney.cavm@...il.com, schwab@...e.de, bamvor.zhangjian@...wei.com,
	philipp.tomsich@...obroma-systems.com, andrey.konovalov@...aro.org,
	christoph.muellner@...obroma-systems.com
Subject: Re: [PATCH v6 14/19] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it

On Wednesday 02 December 2015 14:46:32 Arnd Bergmann wrote:
> On Wednesday 02 December 2015 13:35:22 Yury Norov wrote:
> > On Wed, Dec 02, 2015 at 09:37:05AM +0100, Arnd Bergmann wrote:
> > > The 4*PAGE_SIZE on ARM is an architecture specific oddity, I believe
> > > to work around aliasing caches on ARMv6. As no other architecture does
> > > this, we're probably better off not duplicating it for aarch64-ilp32
> > > and just use sys_shmat as your v6 patch does.
> > >       Arnd
> > 
> > If you feel ARMv6 fix for caches will come soon, just ignore it.
> > Otherwise, please pull it because compat_sys_shmat is broken now
> > for 64K pages.
> > 
> > Signed-off-by: Yury Norov <ynorov@...iumnetworks.com>
> > 
> 
> Sounds good. Will, do you want to take this for the arm64 tree.
> 
> Acked-by: Arnd Bergmann <arnd@...db.de>

(actually Cc Will Deacon)

Will or Catalin, does this look ok to you?

8<----
Subject: fix COMPAT_SHMLBA definition for large pages
From: Yury Norov <ynorov@...iumnetworks.com>

ARM glibc uses (4 * __getpagesize()) for SHMLBA, which is correct for 4KB pages
and works fine for 64KB pages, but the kernel uses a hardcoded 16KB that
is too small for 64KB page based kernels. This changes the definition to
what user space sees when using 64KB pages.

Signed-off-by: Yury Norov <ynorov@...iumnetworks.com>
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 arch/arm64/include/asm/shmparam.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/shmparam.h b/arch/arm64/include/asm/shmparam.h
index 4df608a..e368a55 100644
--- a/arch/arm64/include/asm/shmparam.h
+++ b/arch/arm64/include/asm/shmparam.h
@@ -21,7 +21,7 @@
  * alignment value. Since we don't have aliasing D-caches, the rest of
  * the time we can safely use PAGE_SIZE.
  */
-#define COMPAT_SHMLBA  0x4000
+#define COMPAT_SHMLBA  (4 * PAGE_SIZE)
 
 #include <asm-generic/shmparam.h>
 
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