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From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Christophe Leroy <christophe.leroy@csgroup.eu>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Paul Mackerras <paulus@samba.org>
Cc: "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v1 2/4] powerpc/ftrace: Refactor ftrace_{regs_}caller
Date: Wed, 09 Mar 2022 17:05:29 +0530	[thread overview]
Message-ID: <1646825481.p25t8oi12m.naveen@linux.ibm.com> (raw)
In-Reply-To: <5c0a3a26-ee52-a4f7-9bc2-b38f27a12a76@csgroup.eu>

Christophe Leroy wrote:
> 
> 
> Le 03/03/2022 à 17:59, Naveen N. Rao a écrit :
>> Christophe Leroy wrote:
>>
>> The ability to disable ftrace in certain code paths through 
>> paca_struct->ftrace_enabled will also be relevant on ppc32 - it will be 
>> nice if it can be introduced there.
> 
> Ah ? I understood from commit ea678ac627e0 ("powerpc64/ftrace: Add a 
> field in paca to disable ftrace in unsafe code paths") that it was for 
> when it runs in real mode. PPC32 doesn't run any C code in real mode.

It likely isn't necessary in that case.

> 
> Are there any other situations that real_mode where we'd like to disable 
> it ? If so we could use the thread_struct as we don't have paca on PPC32.

For ppc64, we use this flag to disable certain paths in kvm, kexec, 
mce/hmi and idle/hotplug. If none of those are problematic on ppc32, 
then this isn't necessary.


Thanks,
- Naveen


WARNING: multiple messages have this Message-ID (diff)
From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Christophe Leroy <christophe.leroy@csgroup.eu>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Paul Mackerras <paulus@samba.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH v1 2/4] powerpc/ftrace: Refactor ftrace_{regs_}caller
Date: Wed, 09 Mar 2022 17:05:29 +0530	[thread overview]
Message-ID: <1646825481.p25t8oi12m.naveen@linux.ibm.com> (raw)
In-Reply-To: <5c0a3a26-ee52-a4f7-9bc2-b38f27a12a76@csgroup.eu>

Christophe Leroy wrote:
> 
> 
> Le 03/03/2022 à 17:59, Naveen N. Rao a écrit :
>> Christophe Leroy wrote:
>>
>> The ability to disable ftrace in certain code paths through 
>> paca_struct->ftrace_enabled will also be relevant on ppc32 - it will be 
>> nice if it can be introduced there.
> 
> Ah ? I understood from commit ea678ac627e0 ("powerpc64/ftrace: Add a 
> field in paca to disable ftrace in unsafe code paths") that it was for 
> when it runs in real mode. PPC32 doesn't run any C code in real mode.

It likely isn't necessary in that case.

> 
> Are there any other situations that real_mode where we'd like to disable 
> it ? If so we could use the thread_struct as we don't have paca on PPC32.

For ppc64, we use this flag to disable certain paths in kvm, kexec, 
mce/hmi and idle/hotplug. If none of those are problematic on ppc32, 
then this isn't necessary.


Thanks,
- Naveen


  reply	other threads:[~2022-03-09 11:36 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-17 12:01 [PATCH v1 1/4] powerpc/ftrace: Don't use lmw/stmw in ftrace_regs_caller() Christophe Leroy
2022-02-17 12:01 ` Christophe Leroy
2022-02-17 12:01 ` [PATCH v1 2/4] powerpc/ftrace: Refactor ftrace_{regs_}caller Christophe Leroy
2022-02-17 12:01   ` Christophe Leroy
2022-03-03 16:59   ` Naveen N. Rao
2022-03-03 16:59     ` Naveen N. Rao
2022-03-03 17:39     ` Christophe Leroy
2022-03-03 17:39       ` Christophe Leroy
2022-03-09 11:35       ` Naveen N. Rao [this message]
2022-03-09 11:35         ` Naveen N. Rao
2022-02-17 12:01 ` [PATCH v1 3/4] powerpc/ftrace: Regroup PPC64 specific operations in ftrace_mprofile.S Christophe Leroy
2022-02-17 12:01   ` Christophe Leroy
2022-02-17 12:01 ` [PATCH v1 4/4] powerpc/ftrace: Use STK_GOT " Christophe Leroy
2022-02-17 12:01   ` Christophe Leroy
2022-03-08 12:08 ` [PATCH v1 1/4] powerpc/ftrace: Don't use lmw/stmw in ftrace_regs_caller() Michael Ellerman
2022-03-08 12:08   ` Michael Ellerman

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