* [PATCH] crypto: Fix divide error in do_xor_speed()
@ 2020-12-30 12:17 Kirill Tkhai
2020-12-30 12:59 ` Ard Biesheuvel
0 siblings, 1 reply; 6+ messages in thread
From: Kirill Tkhai @ 2020-12-30 12:17 UTC (permalink / raw)
To: herbert, davem, linux-crypto, linux-kernel, ktkhai
Latest (but not only latest) linux-next panics with divide
error on my QEMU setup.
The patch at the bottom of this message fixes the problem.
xor: measuring software checksum speed
divide error: 0000 [#1] PREEMPT SMP KASAN
PREEMPT SMP KASAN
CPU: 3 PID: 1 Comm: swapper/0 Not tainted 5.10.0-next-20201223+ #2177
RIP: 0010:do_xor_speed+0xbb/0xf3
Code: 41 ff cc 75 b5 bf 01 00 00 00 e8 3d 23 8b fe 65 8b 05 f6 49 83 7d 85 c0 75 05 e8
84 70 81 fe b8 00 00 50 c3 31 d2 48 8d 7b 10 <f7> f5 41 89 c4 e8 58 07 a2 fe 44 89 63 10 48 8d 7b 08
e8 cb 07 a2
RSP: 0000:ffff888100137dc8 EFLAGS: 00010246
RAX: 00000000c3500000 RBX: ffffffff823f0160 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000808 RDI: ffffffff823f0170
RBP: 0000000000000000 R08: ffffffff8109c50f R09: ffffffff824bb6f7
R10: fffffbfff04976de R11: 0000000000000001 R12: 0000000000000000
R13: ffff888101997000 R14: ffff888101994000 R15: ffffffff823f0178
FS: 0000000000000000(0000) GS:ffff8881f7780000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000000220e000 CR4: 00000000000006a0
Call Trace:
calibrate_xor_blocks+0x13c/0x1c4
? do_xor_speed+0xf3/0xf3
do_one_initcall+0xc1/0x1b7
? start_kernel+0x373/0x373
? unpoison_range+0x3a/0x60
kernel_init_freeable+0x1dd/0x238
? rest_init+0xc6/0xc6
kernel_init+0x8/0x10a
ret_from_fork+0x1f/0x30
---[ end trace 5bd3c1d0b77772da ]---
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
---
crypto/xor.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/crypto/xor.c b/crypto/xor.c
index eacbf4f93990..8f899f898ec9 100644
--- a/crypto/xor.c
+++ b/crypto/xor.c
@@ -107,6 +107,8 @@ do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
preempt_enable();
// bytes/ns == GB/s, multiply by 1000 to get MB/s [not MiB/s]
+ if (!min)
+ min = 1;
speed = (1000 * REPS * BENCH_SIZE) / (unsigned int)ktime_to_ns(min);
tmpl->speed = speed;
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] crypto: Fix divide error in do_xor_speed()
2020-12-30 12:17 [PATCH] crypto: Fix divide error in do_xor_speed() Kirill Tkhai
@ 2020-12-30 12:59 ` Ard Biesheuvel
2020-12-30 21:33 ` [PATCH v2] " Kirill Tkhai
0 siblings, 1 reply; 6+ messages in thread
From: Ard Biesheuvel @ 2020-12-30 12:59 UTC (permalink / raw)
To: Kirill Tkhai, Arnd Bergmann, Douglas Anderson
Cc: Herbert Xu, David S. Miller, Linux Crypto Mailing List,
Linux Kernel Mailing List
(+ Arnd, Douglas)
On Wed, 30 Dec 2020 at 13:19, Kirill Tkhai <ktkhai@virtuozzo.com> wrote:
>
> Latest (but not only latest) linux-next panics with divide
> error on my QEMU setup.
>
> The patch at the bottom of this message fixes the problem.
>
> xor: measuring software checksum speed
> divide error: 0000 [#1] PREEMPT SMP KASAN
> PREEMPT SMP KASAN
> CPU: 3 PID: 1 Comm: swapper/0 Not tainted 5.10.0-next-20201223+ #2177
> RIP: 0010:do_xor_speed+0xbb/0xf3
> Code: 41 ff cc 75 b5 bf 01 00 00 00 e8 3d 23 8b fe 65 8b 05 f6 49 83 7d 85 c0 75 05 e8
> 84 70 81 fe b8 00 00 50 c3 31 d2 48 8d 7b 10 <f7> f5 41 89 c4 e8 58 07 a2 fe 44 89 63 10 48 8d 7b 08
> e8 cb 07 a2
> RSP: 0000:ffff888100137dc8 EFLAGS: 00010246
> RAX: 00000000c3500000 RBX: ffffffff823f0160 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: 0000000000000808 RDI: ffffffff823f0170
> RBP: 0000000000000000 R08: ffffffff8109c50f R09: ffffffff824bb6f7
> R10: fffffbfff04976de R11: 0000000000000001 R12: 0000000000000000
> R13: ffff888101997000 R14: ffff888101994000 R15: ffffffff823f0178
> FS: 0000000000000000(0000) GS:ffff8881f7780000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000000 CR3: 000000000220e000 CR4: 00000000000006a0
> Call Trace:
> calibrate_xor_blocks+0x13c/0x1c4
> ? do_xor_speed+0xf3/0xf3
> do_one_initcall+0xc1/0x1b7
> ? start_kernel+0x373/0x373
> ? unpoison_range+0x3a/0x60
> kernel_init_freeable+0x1dd/0x238
> ? rest_init+0xc6/0xc6
> kernel_init+0x8/0x10a
> ret_from_fork+0x1f/0x30
> ---[ end trace 5bd3c1d0b77772da ]---
>
> Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Hello Kirill,
This needs
Fixes: c055e3eae0f1 ("crypto: xor - use ktime for template benchmarking")
Acked-by: Ard Biesheuvel <ardb@kernel.org>
However, I do suspect there is something odd going on here - surely,
it takes time to run these benchmarks, and so a min value of 0x0
suggests that something is broken. So perhaps it is better to simply
set speed to 0x0 in this case as well, and let the calibration routine
pick one an implementation arbitrarily.
> ---
> crypto/xor.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/crypto/xor.c b/crypto/xor.c
> index eacbf4f93990..8f899f898ec9 100644
> --- a/crypto/xor.c
> +++ b/crypto/xor.c
> @@ -107,6 +107,8 @@ do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
> preempt_enable();
>
> // bytes/ns == GB/s, multiply by 1000 to get MB/s [not MiB/s]
> + if (!min)
> + min = 1;
> speed = (1000 * REPS * BENCH_SIZE) / (unsigned int)ktime_to_ns(min);
> tmpl->speed = speed;
>
>
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v2] crypto: Fix divide error in do_xor_speed()
2020-12-30 12:59 ` Ard Biesheuvel
@ 2020-12-30 21:33 ` Kirill Tkhai
2021-01-05 21:24 ` Doug Anderson
2021-01-08 4:41 ` Herbert Xu
0 siblings, 2 replies; 6+ messages in thread
From: Kirill Tkhai @ 2020-12-30 21:33 UTC (permalink / raw)
To: Ard Biesheuvel, Arnd Bergmann, Douglas Anderson
Cc: Herbert Xu, David S. Miller, Linux Crypto Mailing List,
Linux Kernel Mailing List
crypto: Fix divide error in do_xor_speed()
From: Kirill Tkhai <ktkhai@virtuozzo.com>
Latest (but not only latest) linux-next panics with divide
error on my QEMU setup.
The patch at the bottom of this message fixes the problem.
xor: measuring software checksum speed
divide error: 0000 [#1] PREEMPT SMP KASAN
PREEMPT SMP KASAN
CPU: 3 PID: 1 Comm: swapper/0 Not tainted 5.10.0-next-20201223+ #2177
RIP: 0010:do_xor_speed+0xbb/0xf3
Code: 41 ff cc 75 b5 bf 01 00 00 00 e8 3d 23 8b fe 65 8b 05 f6 49 83 7d 85 c0 75 05 e8
84 70 81 fe b8 00 00 50 c3 31 d2 48 8d 7b 10 <f7> f5 41 89 c4 e8 58 07 a2 fe 44 89 63 10 48 8d 7b 08
e8 cb 07 a2
RSP: 0000:ffff888100137dc8 EFLAGS: 00010246
RAX: 00000000c3500000 RBX: ffffffff823f0160 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000808 RDI: ffffffff823f0170
RBP: 0000000000000000 R08: ffffffff8109c50f R09: ffffffff824bb6f7
R10: fffffbfff04976de R11: 0000000000000001 R12: 0000000000000000
R13: ffff888101997000 R14: ffff888101994000 R15: ffffffff823f0178
FS: 0000000000000000(0000) GS:ffff8881f7780000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000000220e000 CR4: 00000000000006a0
Call Trace:
calibrate_xor_blocks+0x13c/0x1c4
? do_xor_speed+0xf3/0xf3
do_one_initcall+0xc1/0x1b7
? start_kernel+0x373/0x373
? unpoison_range+0x3a/0x60
kernel_init_freeable+0x1dd/0x238
? rest_init+0xc6/0xc6
kernel_init+0x8/0x10a
ret_from_fork+0x1f/0x30
---[ end trace 5bd3c1d0b77772da ]---
Fixes: c055e3eae0f1 ("crypto: xor - use ktime for template benchmarking")
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
---
v2: New Year resend :) Added fixes tag.
crypto/xor.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/crypto/xor.c b/crypto/xor.c
index eacbf4f93990..8f899f898ec9 100644
--- a/crypto/xor.c
+++ b/crypto/xor.c
@@ -107,6 +107,8 @@ do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
preempt_enable();
// bytes/ns == GB/s, multiply by 1000 to get MB/s [not MiB/s]
+ if (!min)
+ min = 1;
speed = (1000 * REPS * BENCH_SIZE) / (unsigned int)ktime_to_ns(min);
tmpl->speed = speed;
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v2] crypto: Fix divide error in do_xor_speed()
2020-12-30 21:33 ` [PATCH v2] " Kirill Tkhai
@ 2021-01-05 21:24 ` Doug Anderson
2021-01-08 4:41 ` Herbert Xu
2021-01-08 4:41 ` Herbert Xu
1 sibling, 1 reply; 6+ messages in thread
From: Doug Anderson @ 2021-01-05 21:24 UTC (permalink / raw)
To: Kirill Tkhai
Cc: Ard Biesheuvel, Arnd Bergmann, Herbert Xu, David S. Miller,
Linux Crypto Mailing List, Linux Kernel Mailing List
Hi,
On Wed, Dec 30, 2020 at 1:34 PM Kirill Tkhai <ktkhai@virtuozzo.com> wrote:
>
> crypto: Fix divide error in do_xor_speed()
>
> From: Kirill Tkhai <ktkhai@virtuozzo.com>
>
> Latest (but not only latest) linux-next panics with divide
> error on my QEMU setup.
>
> The patch at the bottom of this message fixes the problem.
>
> xor: measuring software checksum speed
> divide error: 0000 [#1] PREEMPT SMP KASAN
> PREEMPT SMP KASAN
> CPU: 3 PID: 1 Comm: swapper/0 Not tainted 5.10.0-next-20201223+ #2177
> RIP: 0010:do_xor_speed+0xbb/0xf3
> Code: 41 ff cc 75 b5 bf 01 00 00 00 e8 3d 23 8b fe 65 8b 05 f6 49 83 7d 85 c0 75 05 e8
> 84 70 81 fe b8 00 00 50 c3 31 d2 48 8d 7b 10 <f7> f5 41 89 c4 e8 58 07 a2 fe 44 89 63 10 48 8d 7b 08
> e8 cb 07 a2
> RSP: 0000:ffff888100137dc8 EFLAGS: 00010246
> RAX: 00000000c3500000 RBX: ffffffff823f0160 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: 0000000000000808 RDI: ffffffff823f0170
> RBP: 0000000000000000 R08: ffffffff8109c50f R09: ffffffff824bb6f7
> R10: fffffbfff04976de R11: 0000000000000001 R12: 0000000000000000
> R13: ffff888101997000 R14: ffff888101994000 R15: ffffffff823f0178
> FS: 0000000000000000(0000) GS:ffff8881f7780000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000000 CR3: 000000000220e000 CR4: 00000000000006a0
> Call Trace:
> calibrate_xor_blocks+0x13c/0x1c4
> ? do_xor_speed+0xf3/0xf3
> do_one_initcall+0xc1/0x1b7
> ? start_kernel+0x373/0x373
> ? unpoison_range+0x3a/0x60
> kernel_init_freeable+0x1dd/0x238
> ? rest_init+0xc6/0xc6
> kernel_init+0x8/0x10a
> ret_from_fork+0x1f/0x30
> ---[ end trace 5bd3c1d0b77772da ]---
>
> Fixes: c055e3eae0f1 ("crypto: xor - use ktime for template benchmarking")
> Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
> Acked-by: Ard Biesheuvel <ardb@kernel.org>
> ---
>
> v2: New Year resend :) Added fixes tag.
> crypto/xor.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/crypto/xor.c b/crypto/xor.c
> index eacbf4f93990..8f899f898ec9 100644
> --- a/crypto/xor.c
> +++ b/crypto/xor.c
> @@ -107,6 +107,8 @@ do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
> preempt_enable();
>
> // bytes/ns == GB/s, multiply by 1000 to get MB/s [not MiB/s]
> + if (!min)
> + min = 1;
I guess this is if you just have a ktime backend that is not granular
enough for this measurement? So if ktime is backed by a 32kHz clock
then ktime might increment in ~30us increments and maybe we ran in
less time than that?
...so while I think your fix will avoid the crash and could land as a
stopgap, it's a sign that we need to run more repetitions on your
particular setup to get accurate timings. Your patch will probably
cause it to just randomly pick one of the implementations.
Presumably the right thing to do would be to look at
ktime_get_resolution_ns(). If "diff" is ever less than
"ktime_get_resolution_ns() * 10" then we should ramp up the number of
repetitions and try again. The extra "* 10" is to make sure that we'd
be able to tell the difference between faster and slower algorithms.
Perhaps it should actually be more like * 50 or * 100.
-Doug
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2] crypto: Fix divide error in do_xor_speed()
2020-12-30 21:33 ` [PATCH v2] " Kirill Tkhai
2021-01-05 21:24 ` Doug Anderson
@ 2021-01-08 4:41 ` Herbert Xu
1 sibling, 0 replies; 6+ messages in thread
From: Herbert Xu @ 2021-01-08 4:41 UTC (permalink / raw)
To: Kirill Tkhai
Cc: Ard Biesheuvel, Arnd Bergmann, Douglas Anderson, David S. Miller,
Linux Crypto Mailing List, Linux Kernel Mailing List
On Thu, Dec 31, 2020 at 12:33:18AM +0300, Kirill Tkhai wrote:
> crypto: Fix divide error in do_xor_speed()
>
> From: Kirill Tkhai <ktkhai@virtuozzo.com>
>
> Latest (but not only latest) linux-next panics with divide
> error on my QEMU setup.
>
> The patch at the bottom of this message fixes the problem.
>
> xor: measuring software checksum speed
> divide error: 0000 [#1] PREEMPT SMP KASAN
> PREEMPT SMP KASAN
> CPU: 3 PID: 1 Comm: swapper/0 Not tainted 5.10.0-next-20201223+ #2177
> RIP: 0010:do_xor_speed+0xbb/0xf3
> Code: 41 ff cc 75 b5 bf 01 00 00 00 e8 3d 23 8b fe 65 8b 05 f6 49 83 7d 85 c0 75 05 e8
> 84 70 81 fe b8 00 00 50 c3 31 d2 48 8d 7b 10 <f7> f5 41 89 c4 e8 58 07 a2 fe 44 89 63 10 48 8d 7b 08
> e8 cb 07 a2
> RSP: 0000:ffff888100137dc8 EFLAGS: 00010246
> RAX: 00000000c3500000 RBX: ffffffff823f0160 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: 0000000000000808 RDI: ffffffff823f0170
> RBP: 0000000000000000 R08: ffffffff8109c50f R09: ffffffff824bb6f7
> R10: fffffbfff04976de R11: 0000000000000001 R12: 0000000000000000
> R13: ffff888101997000 R14: ffff888101994000 R15: ffffffff823f0178
> FS: 0000000000000000(0000) GS:ffff8881f7780000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000000 CR3: 000000000220e000 CR4: 00000000000006a0
> Call Trace:
> calibrate_xor_blocks+0x13c/0x1c4
> ? do_xor_speed+0xf3/0xf3
> do_one_initcall+0xc1/0x1b7
> ? start_kernel+0x373/0x373
> ? unpoison_range+0x3a/0x60
> kernel_init_freeable+0x1dd/0x238
> ? rest_init+0xc6/0xc6
> kernel_init+0x8/0x10a
> ret_from_fork+0x1f/0x30
> ---[ end trace 5bd3c1d0b77772da ]---
>
> Fixes: c055e3eae0f1 ("crypto: xor - use ktime for template benchmarking")
> Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
> Acked-by: Ard Biesheuvel <ardb@kernel.org>
> ---
>
> v2: New Year resend :) Added fixes tag.
> crypto/xor.c | 2 ++
> 1 file changed, 2 insertions(+)
Patch applied. Thanks.
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2] crypto: Fix divide error in do_xor_speed()
2021-01-05 21:24 ` Doug Anderson
@ 2021-01-08 4:41 ` Herbert Xu
0 siblings, 0 replies; 6+ messages in thread
From: Herbert Xu @ 2021-01-08 4:41 UTC (permalink / raw)
To: Doug Anderson
Cc: Kirill Tkhai, Ard Biesheuvel, Arnd Bergmann, David S. Miller,
Linux Crypto Mailing List, Linux Kernel Mailing List
On Tue, Jan 05, 2021 at 01:24:18PM -0800, Doug Anderson wrote:
>
> ...so while I think your fix will avoid the crash and could land as a
> stopgap, it's a sign that we need to run more repetitions on your
> particular setup to get accurate timings. Your patch will probably
> cause it to just randomly pick one of the implementations.
We can always do a follow-up patch.
Thanks,
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2021-01-08 4:42 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-12-30 12:17 [PATCH] crypto: Fix divide error in do_xor_speed() Kirill Tkhai
2020-12-30 12:59 ` Ard Biesheuvel
2020-12-30 21:33 ` [PATCH v2] " Kirill Tkhai
2021-01-05 21:24 ` Doug Anderson
2021-01-08 4:41 ` Herbert Xu
2021-01-08 4:41 ` Herbert Xu
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