From: Sai Prakash Ranjan <quic_saipraka@quicinc.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Will Deacon <will@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Catalin Marinas <catalin.marinas@arm.com>,
<quic_psodagud@quicinc.com>, "Marc Zyngier" <maz@kernel.org>,
gregkh <gregkh@linuxfoundation.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-arm-msm <linux-arm-msm@vger.kernel.org>,
Ingo Molnar <mingo@redhat.com>
Subject: Re: [PATCHv4 2/2] arm64/io: Add a header for mmio access instrumentation
Date: Mon, 22 Nov 2021 20:29:05 +0530 [thread overview]
Message-ID: <4ed41054-3868-d5e2-9958-56250b7f9be0@quicinc.com> (raw)
In-Reply-To: <CAK8P3a0Zo+PTGAAvisAZamfLUm1ToGZpmHDn-Xk0Eo8TTRGyZg@mail.gmail.com>
On 11/22/2021 8:00 PM, Arnd Bergmann wrote:
> On Mon, Nov 22, 2021 at 3:19 PM Sai Prakash Ranjan
> <quic_saipraka@quicinc.com> wrote:
>> On 11/22/2021 7:29 PM, Arnd Bergmann wrote:
>>> I think this would be a lot less confusing to readers, as it is implemented
>>> exactly in the place that has the normal definition, and it can also have
>>> somewhat more logical semantics by only instrumenting the
>>> normal/relaxed/ioport accessors but not the __raw_* versions that
>>> are meant to be little more than a pointer dereference.
>> But how is this different from logic in atomic-instrumented.h which also
>> has asm-generic version?
>> Initial review few years back mentioned about having something similar
>> to atomic instrumentation
>> and hence it was implemented with the similar approach keeping
>> instrumentation out of arch specific details.
> This is only a cosmetic difference. I usually prefer fewer indirections,
> and I like the way that include/asm-generic/io.h only has all the
> normal 'static inline' definitions spelled out, and calling the __raw_*
> versions. Your version adds an extra layer with the arch_raw_readl(),
> which I'd prefer to avoid.
I'm ok with your preference as long as we have some way to log these
MMIO accesses.
>> And if we do move this instrumentation to asm-generic/io.h, how will
>> that be executed since
>> the arch specifc read{b,w,l,q} overrides this generic version?
> As I understand it, your version also requires architecture specific
> changes, so that would be the same: it only works for architectures
> that get the definition of readl()/readl_relaxed()/inl()/... from
> include/asm-generic/io.h and only override the __raw version. Arnd
Sorry, I didn't get this part, so I am trying this on ARM64:
arm64/include/asm/io.h has read{b,l,w,q} defined.
include/asm-generic/io.h has below:
#ifndef readl
#define readl readl
static inline u32 readl(const volatile void __iomem *addr)
and we include asm-generic/io.h in arm64/include/asm/io.h at the end
after the definitions for arm64 mmio accesors.
So arch implementation here overrides generic ones as I see it, am I
missing something? I even confirmed this
with some trace_printk to generic and arch specific definitions of readl
and I see arch specific ones being called.
Thanks,
Sai
next prev parent reply other threads:[~2021-11-22 14:59 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-15 11:33 [PATCHv4 0/2] tracing/rwmmio/arm64: Add support to trace register reads/writes Sai Prakash Ranjan
2021-11-15 11:33 ` [PATCHv4 1/2] tracing: Add register read/write tracing support Sai Prakash Ranjan
2021-11-19 13:43 ` Marc Zyngier
2021-11-19 14:07 ` Sai Prakash Ranjan
2021-11-19 14:17 ` Marc Zyngier
2021-11-19 15:19 ` Sai Prakash Ranjan
2021-11-15 11:33 ` [PATCHv4 2/2] arm64/io: Add a header for mmio access instrumentation Sai Prakash Ranjan
2021-11-16 22:40 ` Steven Rostedt
2021-11-17 3:53 ` Sai Prakash Ranjan
2021-11-18 14:58 ` kernel test robot
2021-11-18 15:24 ` Arnd Bergmann
2021-11-19 4:06 ` Sai Prakash Ranjan
2021-11-22 13:35 ` Sai Prakash Ranjan
2021-11-22 13:59 ` Arnd Bergmann
2021-11-22 14:19 ` Sai Prakash Ranjan
2021-11-22 14:30 ` Arnd Bergmann
2021-11-22 14:59 ` Sai Prakash Ranjan [this message]
2021-11-22 15:35 ` Arnd Bergmann
2021-11-22 15:43 ` Sai Prakash Ranjan
2021-11-29 13:49 ` Sai Prakash Ranjan
2021-11-19 13:48 ` Marc Zyngier
2021-11-19 14:09 ` Sai Prakash Ranjan
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