From: Dan Raymond <raymod2@gmail.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Greg KH <gregkh@linuxfoundation.org>,
linux-kernel@vger.kernel.org, x86@kernel.org,
linux-serial <linux-serial@vger.kernel.org>,
tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
dave.hansen@linux.intel.com, hpa@zytor.com, peterz@infradead.org,
andriy.shevchenko@linux.intel.com, quic_saipraka@quicinc.com
Subject: Re: [PATCH v3] arch/x86: port I/O tracing on x86
Date: Fri, 6 Oct 2023 15:29:18 -0600 [thread overview]
Message-ID: <3d30d1b1-e4a2-7af3-20ef-11d2d97f65ad@gmail.com> (raw)
In-Reply-To: <20231004195001.76a57417@gandalf.local.home>
On 10/4/2023 5:50 PM, Steven Rostedt wrote:
>> I've copied Steven Rostedt who is the maintainer of tracefs to see if he
>> has any comment. I just noticed arch/x86/boot/msr.h and I see that it
>> redefines rdmsr() and wrmsr() and omits the tracepoints. A comment there
>> explains:
>>
>> /*
>> * The kernel proper already defines rdmsr()/wrmsr(), but they are not for the
>> * boot kernel since they rely on tracepoint/exception handling infrastructure
>> * that's not available here.
>> */
>>
>> We could do something similar for inb()/outb() and redefine them in
>> arch/x86/boot/io.h instead of including <asm/shared/io.h> there.
>
> That would be a saner approach.
>
> -- Steve
I tried this but it is problematic because there are include chains that
define inb()/outb() without including arch/x86/boot/io.h at all. For example:
arch/x86/boot/compressed/misc.c ->
arch/x86/boot/compressed/misc.h ->
include/linux/acpi.h ->
include/acpi/acpi_io.h ->
include/linux/io.h ->
arch/x86/include/asm/io.h ->
arch/x86/include/asm/shared/io.h
What we need is to disable tracepoints altogether in arch/x86/boot/* so I
added -DDISABLE_TRACEPOINTS to the relevant Makefiles and I added a check for
that symbol in tracepoint-defs.h. I will submit a v4 version of my patch
with these changes shortly.
This resolves the problem with <asm/msr.h> as well. After applying the v4
patch I was able to call rdmsr()/wrmsr() from arch/x86/boot/misc.c.
Theoretically we can now remove arch/x86/boot/msr.h but I had trouble with
that due to compiler warnings and errors. The include files in arch/x86/boot
are a mess. Maybe this can be cleaned up in another patch.
next prev parent reply other threads:[~2023-10-06 21:29 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-29 19:15 [PATCH v3] arch/x86: port I/O tracing on x86 Dan Raymond
2023-10-03 12:50 ` Greg KH
2023-10-04 22:54 ` Dan Raymond
2023-10-04 23:50 ` Steven Rostedt
2023-10-06 21:29 ` Dan Raymond [this message]
2023-10-06 21:32 ` [PATCH v4] " Dan Raymond
2023-10-07 6:53 ` kernel test robot
2023-10-07 17:56 ` [PATCH v5] " Dan Raymond
2023-10-11 20:22 ` Dan Raymond
2023-10-11 20:41 ` Greg KH
2023-10-21 16:00 ` Greg KH
2023-10-21 20:15 ` Steven Rostedt
2023-10-23 21:29 ` Dan Raymond
2023-10-23 21:51 ` Steven Rostedt
2023-10-23 20:28 ` Dan Raymond
2023-10-24 9:32 ` Greg KH
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