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Thu, 20 Jun 2024 05:04:47 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGXBwop604Y5LJHb0b34gI7Je4i9x8IkF784us5Ea9E+Z1DVF2QvWsWClXZaaHI9SoMFqaGOw== X-Received: by 2002:ad4:5c8b:0:b0:6b5:6f9:9207 with SMTP id 6a1803df08f44-6b506f9925dmr56113586d6.20.1718885086970; Thu, 20 Jun 2024 05:04:46 -0700 (PDT) Received: from [10.26.1.93] ([66.187.232.136]) by smtp.gmail.com with ESMTPSA id af79cd13be357-79bc266c496sm84674985a.20.2024.06.20.05.04.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 20 Jun 2024 05:04:46 -0700 (PDT) Message-ID: <4aff3fb4-cf1b-4c09-918a-3c4252a34bd6@redhat.com> Date: Thu, 20 Jun 2024 08:04:45 -0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] ACPI: Do not enable ACPI SPCR console by default on arm64 To: Liu Wei , sudeep.holla@arm.com, Will Deacon Cc: catalin.marinas@arm.com, guohanjun@huawei.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, lpieralisi@kernel.org, rafael@kernel.org References: <20240530015332.7305-1-liuwei09@cestc.cn> <20240618152923.GB2354@willie-the-truck> <20240618164024.tehpbscax47jkluj@bogus> Content-Language: en-US From: Prarit Bhargava In-Reply-To: <20240618164024.tehpbscax47jkluj@bogus> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 6/18/24 23:43, Liu Wei wrote: > From: Sudeep Holla > > On Tue, Jun 18, 2024 at 04:29:24PM +0100, Will Deacon wrote: >>> On Thu, May 30, 2024 at 09:06:17AM -0400, Prarit Bhargava wrote: >>>> On 5/29/24 21:53, Liu Wei wrote: >>>>> Consistency with x86 and loongarch, don't enable ACPI SPCR console >>>>> by default on arm64 >>>>> >>>>> Signed-off-by: Liu Wei >>>>> --- >>>>> arch/arm64/kernel/acpi.c | 3 ++- >>>>> 1 file changed, 2 insertions(+), 1 deletion(-) >>>>> >>>>> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c >>>>> index dba8fcec7f33..1deda3e5a0d2 100644 >>>>> --- a/arch/arm64/kernel/acpi.c >>>>> +++ b/arch/arm64/kernel/acpi.c >>>>> @@ -227,7 +227,8 @@ void __init acpi_boot_table_init(void) >>>>> if (earlycon_acpi_spcr_enable) >>>>> early_init_dt_scan_chosen_stdout(); >>>>> } else { >>>>> - acpi_parse_spcr(earlycon_acpi_spcr_enable, true); >>>>> + /* Do not enable ACPI SPCR console by default */ >>>>> + acpi_parse_spcr(earlycon_acpi_spcr_enable, false); >>>>> if (IS_ENABLED(CONFIG_ACPI_BGRT)) >>>>> acpi_table_parse(ACPI_SIG_BGRT, acpi_parse_bgrt); >>>>> } >>>> >>>> It's been a while, and the status of arm hardware may have changed. IIRC the >>>> choice to force enable this is that most arm hardware is headless and this >>>> was a _required_ option for booting. >>>> >>>> I'm not sure if that's still the case as it's been a long time. >>>> >>>> Can anyone from the ARM community provide an approval here? >>> >>> I don't have a strong opinion either way, but adding the Arm ACPI folks >>> in case they care. >>> >>> Having said that, if the only rationale for this patch is consistency >>> with other architectures, then I think I'd lean towards leaving the >>> behaviour as-is so we don't give users a nasty surprise on their next >>> kernel upgrade. >>> >> >> +1, I am concerned about breaking existing behaviour on the platforms >> in the wild. Also many platforms running ACPI would have already used >> console cmdline parameter if SPCR is not their choice for the console. >> So I don't see the need to align with other arch default behaviour here, >> we can revisit if someone shouts with a real reason as why cmdline option >> is not viable. > > For varying privacy and security reasons, sometimes we would like to > completely silence the serial console output, and only enable it through > cmdline when needed. > FWIW, I understand that concern but the feedback you're receiving is that there are many existing systems that depend on this behavior. Breaking users for your concerns is not a good idea. Perhaps a solution is to add yet-another-config-option, or add a kernel parameter to disable the SPCR console on ARM? Something like "acpi=nospcr"? P. > On ARM, it is difficult because SPCR is enabled by default. > > Thanks for your patience, > Liu Wei > >> >> -- >> Regards, >> Sudeep > > > > From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.cecloud.com (unknown [1.203.97.246]) by smtp.subspace.kernel.org (Postfix) with ESMTP id AA38CEBE for ; Fri, 21 Jun 2024 04:38:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=1.203.97.246 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718944734; cv=none; b=hijyPPR1J8HXdHzoKo0TnjBd+zNNDiV7wtRaETwX1QMSU0m2Clg0xM9rQ2ViojH74rKHbH9f9Mkczh6TbdfNrucZKkZOdtk0QWBMFGJqlaPFyJst2BaYLfIF6qKGsUfJj7NS5EGWrkFBhTEITYbgc4mVTzL96AW1vUQN3FvHQq0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718944734; c=relaxed/simple; bh=id8v/eoj4gY4o6m8alH66zYbMJAteMfjVfD2GcRbCGA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=c8ynSjQ6sQ3M16QJdvKeio5KD8Li3N6gBJTDve+vuLmfNIES3qo7RsO8Lw/5tjw0u4FMzgFhk0nzKt/Y12Gk/UjZaAH0FjvLpmEvtY/xeSf37CfAtdxZNIa1PM9suTB9nVilYONbjT8fAVGnUx7B5lvFhIsKcejei0loVYZmwIc= ARC-Authentication-Results:i=1; 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Fri, 21 Jun 2024 12:38:41 +0800 (CST) X-IP-DOMAINF:1 X-RL-SENDER:liuwei09@cestc.cn X-SENDER:liuwei09@cestc.cn X-LOGIN-NAME:liuwei09@cestc.cn X-FST-TO:prarit@redhat.com X-RCPT-COUNT:10 X-LOCAL-RCPT-COUNT:1 X-MUTI-DOMAIN-COUNT:0 X-SENDER-IP:111.48.69.245 X-ATTACHMENT-NUM:0 X-UNIQUE-TAG: X-System-Flag:0 From: Liu Wei To: prarit@redhat.com, Liu Wei , sudeep.holla@arm.com, Will Deacon Cc: catalin.marinas@arm.com, guohanjun@huawei.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, lpieralisi@kernel.org, rafael@kernel.org Subject: Re: [PATCH] ACPI: Do not enable ACPI SPCR console by default on arm64 Date: Fri, 21 Jun 2024 12:37:50 +0800 Message-ID: <4aff3fb4-cf1b-4c09-918a-3c4252a34bd6@redhat.com> X-Mailer: git-send-email 2.42.1 In-Reply-To: <20240618164024.tehpbscax47jkluj@bogus> References: <20240530015332.7305-1-liuwei09@cestc.cn> <20240618152923.GB2354@willie-the-truck> <20240618164024.tehpbscax47jkluj@bogus> Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F32611A00C2 for ; 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Thu, 20 Jun 2024 05:04:47 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGXBwop604Y5LJHb0b34gI7Je4i9x8IkF784us5Ea9E+Z1DVF2QvWsWClXZaaHI9SoMFqaGOw== X-Received: by 2002:ad4:5c8b:0:b0:6b5:6f9:9207 with SMTP id 6a1803df08f44-6b506f9925dmr56113586d6.20.1718885086970; Thu, 20 Jun 2024 05:04:46 -0700 (PDT) Received: from [10.26.1.93] ([66.187.232.136]) by smtp.gmail.com with ESMTPSA id af79cd13be357-79bc266c496sm84674985a.20.2024.06.20.05.04.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 20 Jun 2024 05:04:46 -0700 (PDT) Precedence: bulk Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Message-ID: <20240621043750.Ye7FN-uIzztofO-vM9AfRd_SzwMemGA5t9Xn6qZPDk4@z> From: Prarit Bhargava > On 6/18/24 23:43, Liu Wei wrote: > > From: Sudeep Holla > > > > On Tue, Jun 18, 2024 at 04:29:24PM +0100, Will Deacon wrote: > >>> On Thu, May 30, 2024 at 09:06:17AM -0400, Prarit Bhargava wrote: > >>>> On 5/29/24 21:53, Liu Wei wrote: > >>>>> Consistency with x86 and loongarch, don't enable ACPI SPCR console > >>>>> by default on arm64 > >>>>> > >>>>> Signed-off-by: Liu Wei > >>>>> --- > >>>>> arch/arm64/kernel/acpi.c | 3 ++- > >>>>> 1 file changed, 2 insertions(+), 1 deletion(-) > >>>>> > >>>>> diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c > >>>>> index dba8fcec7f33..1deda3e5a0d2 100644 > >>>>> --- a/arch/arm64/kernel/acpi.c > >>>>> +++ b/arch/arm64/kernel/acpi.c > >>>>> @@ -227,7 +227,8 @@ void __init acpi_boot_table_init(void) > >>>>> if (earlycon_acpi_spcr_enable) > >>>>> early_init_dt_scan_chosen_stdout(); > >>>>> } else { > >>>>> - acpi_parse_spcr(earlycon_acpi_spcr_enable, true); > >>>>> + /* Do not enable ACPI SPCR console by default */ > >>>>> + acpi_parse_spcr(earlycon_acpi_spcr_enable, false); > >>>>> if (IS_ENABLED(CONFIG_ACPI_BGRT)) > >>>>> acpi_table_parse(ACPI_SIG_BGRT, acpi_parse_bgrt); > >>>>> } > >>>> > >>>> It's been a while, and the status of arm hardware may have changed. IIRC the > >>>> choice to force enable this is that most arm hardware is headless and this > >>>> was a _required_ option for booting. > >>>> > >>>> I'm not sure if that's still the case as it's been a long time. > >>>> > >>>> Can anyone from the ARM community provide an approval here? > >>> > >>> I don't have a strong opinion either way, but adding the Arm ACPI folks > >>> in case they care. > >>> > >>> Having said that, if the only rationale for this patch is consistency > >>> with other architectures, then I think I'd lean towards leaving the > >>> behaviour as-is so we don't give users a nasty surprise on their next > >>> kernel upgrade. > >>> > >> > >> +1, I am concerned about breaking existing behaviour on the platforms > >> in the wild. Also many platforms running ACPI would have already used > >> console cmdline parameter if SPCR is not their choice for the console. > >> So I don't see the need to align with other arch default behaviour here, > >> we can revisit if someone shouts with a real reason as why cmdline option > >> is not viable. > > > > For varying privacy and security reasons, sometimes we would like to > > completely silence the serial console output, and only enable it through > > cmdline when needed. > > > > FWIW, I understand that concern but the feedback you're receiving is > that there are many existing systems that depend on this behavior. > Breaking users for your concerns is not a good idea. > > Perhaps a solution is to add yet-another-config-option, or add a kernel > parameter to disable the SPCR console on ARM? > > Something like "acpi=nospcr"? Thank you for your suggestion, I will send the new version later. Best wishes, Liu wei > > P. > > > On ARM, it is difficult because SPCR is enabled by default. > > > > Thanks for your patience, > > Liu Wei > > > >> > >> -- > >> Regards, > >> Sudeep > >