* [PATCH 1/9] mm/maccess: fix unaligned copy_{from,to}_kernel_nofault
[not found] <20200907153701.2981205-1-arnd@arndb.de>
@ 2020-09-07 15:36 ` Arnd Bergmann
2020-09-08 6:11 ` Christoph Hellwig
2020-09-27 9:25 ` Linus Walleij
0 siblings, 2 replies; 5+ messages in thread
From: Arnd Bergmann @ 2020-09-07 15:36 UTC (permalink / raw)
To: Christoph Hellwig, Russell King
Cc: Alexander Viro, kernel, linux-arch, linux-arm-kernel,
linus.walleij, Arnd Bergmann, Andrew Morton, Daniel Borkmann,
Alexei Starovoitov, linux-mm, linux-kernel
On machines such as ARMv5 that trap unaligned accesses, these
two functions can be slow when each access needs to be emulated,
or they might not work at all.
Change them so that each loop is only used when both the src
and dst pointers are naturally aligned.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
mm/maccess.c | 28 ++++++++++++++++++++++------
1 file changed, 22 insertions(+), 6 deletions(-)
diff --git a/mm/maccess.c b/mm/maccess.c
index 3bd70405f2d8..d3f1a1f0b1c1 100644
--- a/mm/maccess.c
+++ b/mm/maccess.c
@@ -24,13 +24,21 @@ bool __weak copy_from_kernel_nofault_allowed(const void *unsafe_src,
long copy_from_kernel_nofault(void *dst, const void *src, size_t size)
{
+ unsigned long align = 0;
+
+ if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
+ align = (unsigned long)dst | (unsigned long)src;
+
if (!copy_from_kernel_nofault_allowed(src, size))
return -ERANGE;
pagefault_disable();
- copy_from_kernel_nofault_loop(dst, src, size, u64, Efault);
- copy_from_kernel_nofault_loop(dst, src, size, u32, Efault);
- copy_from_kernel_nofault_loop(dst, src, size, u16, Efault);
+ if (!(align & 7))
+ copy_from_kernel_nofault_loop(dst, src, size, u64, Efault);
+ if (!(align & 3))
+ copy_from_kernel_nofault_loop(dst, src, size, u32, Efault);
+ if (!(align & 1))
+ copy_from_kernel_nofault_loop(dst, src, size, u16, Efault);
copy_from_kernel_nofault_loop(dst, src, size, u8, Efault);
pagefault_enable();
return 0;
@@ -50,10 +58,18 @@ EXPORT_SYMBOL_GPL(copy_from_kernel_nofault);
long copy_to_kernel_nofault(void *dst, const void *src, size_t size)
{
+ unsigned long align = 0;
+
+ if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
+ align = (unsigned long)dst | (unsigned long)src;
+
pagefault_disable();
- copy_to_kernel_nofault_loop(dst, src, size, u64, Efault);
- copy_to_kernel_nofault_loop(dst, src, size, u32, Efault);
- copy_to_kernel_nofault_loop(dst, src, size, u16, Efault);
+ if (!(align & 7))
+ copy_to_kernel_nofault_loop(dst, src, size, u64, Efault);
+ if (!(align & 3))
+ copy_to_kernel_nofault_loop(dst, src, size, u32, Efault);
+ if (!(align & 1))
+ copy_to_kernel_nofault_loop(dst, src, size, u16, Efault);
copy_to_kernel_nofault_loop(dst, src, size, u8, Efault);
pagefault_enable();
return 0;
--
2.27.0
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 1/9] mm/maccess: fix unaligned copy_{from,to}_kernel_nofault
2020-09-07 15:36 ` [PATCH 1/9] mm/maccess: fix unaligned copy_{from,to}_kernel_nofault Arnd Bergmann
@ 2020-09-08 6:11 ` Christoph Hellwig
2020-09-27 9:25 ` Linus Walleij
1 sibling, 0 replies; 5+ messages in thread
From: Christoph Hellwig @ 2020-09-08 6:11 UTC (permalink / raw)
To: Arnd Bergmann
Cc: Christoph Hellwig, Russell King, Alexander Viro, kernel,
linux-arch, linux-arm-kernel, linus.walleij, Andrew Morton,
Daniel Borkmann, Alexei Starovoitov, linux-mm, linux-kernel
Looks good:
Reviewed-by: Christoph Hellwig <hch@lst.de>
This should probably go into Al's base.set_fs branch.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 1/9] mm/maccess: fix unaligned copy_{from,to}_kernel_nofault
2020-09-07 15:36 ` [PATCH 1/9] mm/maccess: fix unaligned copy_{from,to}_kernel_nofault Arnd Bergmann
2020-09-08 6:11 ` Christoph Hellwig
@ 2020-09-27 9:25 ` Linus Walleij
1 sibling, 0 replies; 5+ messages in thread
From: Linus Walleij @ 2020-09-27 9:25 UTC (permalink / raw)
To: Arnd Bergmann
Cc: Christoph Hellwig, Russell King, Alexander Viro,
linux-kernel@vger.kernel.org, linux-arch, Linux ARM,
Andrew Morton, Daniel Borkmann, Alexei Starovoitov, linux-mm,
linux-kernel
On Mon, Sep 7, 2020 at 5:37 PM Arnd Bergmann <arnd@arndb.de> wrote:
> On machines such as ARMv5 that trap unaligned accesses, these
> two functions can be slow when each access needs to be emulated,
> or they might not work at all.
>
> Change them so that each loop is only used when both the src
> and dst pointers are naturally aligned.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
That's a clever optimization idea, nice!
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Yours,
Linus Walleij
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 1/9] mm/maccess: fix unaligned copy_{from,to}_kernel_nofault
2020-10-30 15:49 ` [PATCH 1/9] mm/maccess: fix unaligned copy_{from,to}_kernel_nofault Arnd Bergmann
@ 2020-11-06 8:57 ` Linus Walleij
0 siblings, 0 replies; 5+ messages in thread
From: Linus Walleij @ 2020-11-06 8:57 UTC (permalink / raw)
To: Arnd Bergmann
Cc: Russell King, Christoph Hellwig, linux-kernel, Linux ARM,
Linux-Arch, Linux Memory Management List, Al Viro, Arnd Bergmann
On Fri, Oct 30, 2020 at 4:49 PM Arnd Bergmann <arnd@kernel.org> wrote:
> From: Arnd Bergmann <arnd@arndb.de>
>
> On machines such as ARMv5 that trap unaligned accesses, these
> two functions can be slow when each access needs to be emulated,
> or they might not work at all.
>
> Change them so that each loop is only used when both the src
> and dst pointers are naturally aligned.
>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Yours,
Linus Walleij
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH 1/9] mm/maccess: fix unaligned copy_{from,to}_kernel_nofault
2020-10-30 15:45 [PATCH v4 0/9] ARM: remove set_fs callers and implementation Arnd Bergmann
@ 2020-10-30 15:49 ` Arnd Bergmann
2020-11-06 8:57 ` Linus Walleij
0 siblings, 1 reply; 5+ messages in thread
From: Arnd Bergmann @ 2020-10-30 15:49 UTC (permalink / raw)
To: Russell King, Christoph Hellwig
Cc: linux-kernel, linux-arm-kernel, linux-arch, linux-mm, viro,
linus.walleij, arnd
From: Arnd Bergmann <arnd@arndb.de>
On machines such as ARMv5 that trap unaligned accesses, these
two functions can be slow when each access needs to be emulated,
or they might not work at all.
Change them so that each loop is only used when both the src
and dst pointers are naturally aligned.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
mm/maccess.c | 28 ++++++++++++++++++++++------
1 file changed, 22 insertions(+), 6 deletions(-)
diff --git a/mm/maccess.c b/mm/maccess.c
index 3bd70405f2d8..d3f1a1f0b1c1 100644
--- a/mm/maccess.c
+++ b/mm/maccess.c
@@ -24,13 +24,21 @@ bool __weak copy_from_kernel_nofault_allowed(const void *unsafe_src,
long copy_from_kernel_nofault(void *dst, const void *src, size_t size)
{
+ unsigned long align = 0;
+
+ if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
+ align = (unsigned long)dst | (unsigned long)src;
+
if (!copy_from_kernel_nofault_allowed(src, size))
return -ERANGE;
pagefault_disable();
- copy_from_kernel_nofault_loop(dst, src, size, u64, Efault);
- copy_from_kernel_nofault_loop(dst, src, size, u32, Efault);
- copy_from_kernel_nofault_loop(dst, src, size, u16, Efault);
+ if (!(align & 7))
+ copy_from_kernel_nofault_loop(dst, src, size, u64, Efault);
+ if (!(align & 3))
+ copy_from_kernel_nofault_loop(dst, src, size, u32, Efault);
+ if (!(align & 1))
+ copy_from_kernel_nofault_loop(dst, src, size, u16, Efault);
copy_from_kernel_nofault_loop(dst, src, size, u8, Efault);
pagefault_enable();
return 0;
@@ -50,10 +58,18 @@ EXPORT_SYMBOL_GPL(copy_from_kernel_nofault);
long copy_to_kernel_nofault(void *dst, const void *src, size_t size)
{
+ unsigned long align = 0;
+
+ if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
+ align = (unsigned long)dst | (unsigned long)src;
+
pagefault_disable();
- copy_to_kernel_nofault_loop(dst, src, size, u64, Efault);
- copy_to_kernel_nofault_loop(dst, src, size, u32, Efault);
- copy_to_kernel_nofault_loop(dst, src, size, u16, Efault);
+ if (!(align & 7))
+ copy_to_kernel_nofault_loop(dst, src, size, u64, Efault);
+ if (!(align & 3))
+ copy_to_kernel_nofault_loop(dst, src, size, u32, Efault);
+ if (!(align & 1))
+ copy_to_kernel_nofault_loop(dst, src, size, u16, Efault);
copy_to_kernel_nofault_loop(dst, src, size, u8, Efault);
pagefault_enable();
return 0;
--
2.27.0
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2020-11-06 8:57 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
[not found] <20200907153701.2981205-1-arnd@arndb.de>
2020-09-07 15:36 ` [PATCH 1/9] mm/maccess: fix unaligned copy_{from,to}_kernel_nofault Arnd Bergmann
2020-09-08 6:11 ` Christoph Hellwig
2020-09-27 9:25 ` Linus Walleij
2020-10-30 15:45 [PATCH v4 0/9] ARM: remove set_fs callers and implementation Arnd Bergmann
2020-10-30 15:49 ` [PATCH 1/9] mm/maccess: fix unaligned copy_{from,to}_kernel_nofault Arnd Bergmann
2020-11-06 8:57 ` Linus Walleij
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox