From: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
To: Anton Blanchard <anton@samba.org>, Michael Ellerman <mpe@ellerman.id.au>
Cc: Andrew Donnellan <andrew.donnellan@au1.ibm.com>,
chris@distroguy.com, aneesh.kumar@linux.vnet.ibm.com,
ast@kernel.org, linux-kernel@vger.kernel.org, oss@buserror.net,
paul.gortmaker@windriver.com, duwe@lst.de,
lsorense@csclub.uwaterloo.ca, bauerman@linux.vnet.ibm.com,
oohall@gmail.com, naveen.n.rao@linux.vnet.ibm.com,
linuxppc-dev@lists.ozlabs.org, paulus@samba.org,
viro@zeniv.linux.org.uk,
Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Subject: Re: [PATCH 1/3] powerpc: Emulation support for load/store instructions on LE
Date: Mon, 7 Nov 2016 00:29:04 +0530 [thread overview]
Message-ID: <581F7D78.1040008@linux.vnet.ibm.com> (raw)
In-Reply-To: <20161106063151.3ef04e9e@kryten>
On Sunday 06 November 2016 01:01 AM, Anton Blanchard wrote:
> Hi,
>
>> kprobe, uprobe, hw-breakpoint and xmon are the only user of
>> emulate_step.
>>
>> Kprobe / uprobe single-steps instruction if they can't emulate it, so
>> there is no problem with them. As I mention, hw-breakpoint is broken.
>> However I'm not sure about xmon, I need to check that.
> I was mostly concerned that it would impact kprobes. Sounds like we are
> ok there.
>
>> So yes, there is no user-visible feature that depends on this.
> Aren't hardware breakpoints exposed via perf? I'd call perf
> user-visible.
Thanks Anton, That's a good catch. I tried this on ppc64le:
$ sudo cat /proc/kallsyms | grep pid_max
c00000000116998c D pid_max
$ sudo ./perf record -a --event=mem:0xc00000000116998c sleep 10
Before patch:
It does not record any data and throws below warning.
$ dmesg
[ 817.895573] Unable to handle hardware breakpoint. Breakpoint at 0xc00000000116998c will be disabled.
[ 817.895581] ------------[ cut here ]------------
[ 817.895588] WARNING: CPU: 24 PID: 2032 at arch/powerpc/kernel/hw_breakpoint.c:277 hw_breakpoint_handler+0x124/0x230
...
After patch:
It records data properly.
$ sudo ./perf report --stdio
...
# Samples: 36 of event 'mem:0xc00000000116998c'
# Event count (approx.): 36
#
# Overhead Command Shared Object Symbol
# ........ ............. ................ .............
#
63.89% kdumpctl [kernel.vmlinux] [k] alloc_pid
27.78% opal_errd [kernel.vmlinux] [k] alloc_pid
5.56% kworker/u97:4 [kernel.vmlinux] [k] alloc_pid
2.78% systemd [kernel.vmlinux] [k] alloc_pid
-Ravi
next prev parent reply other threads:[~2016-11-06 18:59 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-02 8:53 [PATCH 0/3] powerpc: Emulation support for load/store instructions on LE Ravi Bangoria
2016-11-02 8:53 ` [PATCH 1/3] " Ravi Bangoria
2016-11-02 21:04 ` Anton Blanchard
2016-11-03 5:41 ` Ravi Bangoria
2016-11-03 9:48 ` Michael Ellerman
2016-11-03 10:27 ` Ravi Bangoria
2016-11-04 2:07 ` Andrew Donnellan
2016-11-04 5:31 ` Ravi Bangoria
2016-11-05 19:31 ` Anton Blanchard
2016-11-06 18:59 ` Ravi Bangoria [this message]
2016-11-02 8:53 ` [PATCH 2/3] powerpc: Add encoding for couple of load/store instructions Ravi Bangoria
2016-11-02 8:53 ` [PATCH 3/3] powerpc: emulate_step test for " Ravi Bangoria
2016-11-02 10:30 ` Naveen N. Rao
2016-11-03 7:03 ` [PATCH 0/3] powerpc: Emulation support for load/store instructions on LE Naveen N. Rao
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