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From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: "Russell King" <linux@armlinux.org.uk>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	"Kees Cook" <keescook@chromium.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Masahiro Yamada" <masahiroy@kernel.org>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	"Sami Tolvanen" <samitolvanen@google.com>,
	"Colin Ian King" <colin.king@canonical.com>,
	"Frederic Weisbecker" <frederic@kernel.org>,
	"Mike Rapoport" <rppt@kernel.org>,
	"YiFei Zhu" <yifeifz2@illinois.edu>,
	"Steven Rostedt (VMware)" <rostedt@goodmis.org>,
	"Viresh Kumar" <viresh.kumar@linaro.org>,
	"Andrey Konovalov" <andreyknvl@gmail.com>,
	"Wang Kefeng" <wangkefeng.wang@huawei.com>,
	"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
	"Nathan Chancellor" <nathan@kernel.org>,
	"Nick Desaulniers" <ndesaulniers@google.com>,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	"Alexei Starovoitov" <ast@kernel.org>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	bpf@vger.kernel.org
Subject: Re: [PATCH v2 1/2] arch/Kconfig: Make CONFIG_CPU_SPECTRE available for all architectures
Date: Thu, 28 Oct 2021 12:36:58 -0700	[thread overview]
Message-ID: <20211028193658.7n2oehp6yogyqbwq@gupta-dev2.localdomain> (raw)
In-Reply-To: <20211028134918.GB48435@lakrids.cambridge.arm.com>

On 28.10.2021 14:49, Mark Rutland wrote:
>On Wed, Oct 27, 2021 at 06:33:22PM -0700, Pawan Gupta wrote:
>> Borrow CONFIG_CPU_SPECTRE from ARM to be available for all
>> architectures. This will help in configuration of features that depend
>> on CPU being affected by spectre class of vulnerabilities.
>>
>> Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
>
>Given that spectre isn't one specific issue, biut rather a blanket term
>for a bunch of things that can have variable overlap, I don't think this
>makes much sense unless we're going to add finer-grained options for all
>the variants, and IMO it'd make more sene for the architectures to
>directly select the things that'd otherwise be dependent on this.

Isn't ARM already using CPU_SPECTRE for selecting things: 

	config HARDEN_BRANCH_PREDICTOR
	     bool "Harden the branch predictor against aliasing attacks" if EXPERT
	     depends on CPU_SPECTRE

This was the whole motivation for doing the same for x86.

Adding a condition for all architectures is also okay, but its going to
a little messier:

	 config BPF_UNPRIV_DEFAULT_OFF
	        default y if X86 || ARM || ... 

This approach would make sense if architectures wants to explicitly
select the defaults irrespective of architecture being affected by
spectre.

If that's the case I will change the BPF_UNPRIV_DEFAULT_OFF default to
depend on architecture. I hope BPF maintainer, Daniel is okay with it?

Pawan

Added BPF maintainers and bpf@vger to cc.

WARNING: multiple messages have this Message-ID (diff)
From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: "Russell King" <linux@armlinux.org.uk>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	"Kees Cook" <keescook@chromium.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Masahiro Yamada" <masahiroy@kernel.org>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	"Sami Tolvanen" <samitolvanen@google.com>,
	"Colin Ian King" <colin.king@canonical.com>,
	"Frederic Weisbecker" <frederic@kernel.org>,
	"Mike Rapoport" <rppt@kernel.org>,
	"YiFei Zhu" <yifeifz2@illinois.edu>,
	"Steven Rostedt (VMware)" <rostedt@goodmis.org>,
	"Viresh Kumar" <viresh.kumar@linaro.org>,
	"Andrey Konovalov" <andreyknvl@gmail.com>,
	"Wang Kefeng" <wangkefeng.wang@huawei.com>,
	"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
	"Nathan Chancellor" <nathan@kernel.org>,
	"Nick Desaulniers" <ndesaulniers@google.com>,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	"Alexei Starovoitov" <ast@kernel.org>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	bpf@vger.kernel.org
Subject: Re: [PATCH v2 1/2] arch/Kconfig: Make CONFIG_CPU_SPECTRE available for all architectures
Date: Thu, 28 Oct 2021 12:36:58 -0700	[thread overview]
Message-ID: <20211028193658.7n2oehp6yogyqbwq@gupta-dev2.localdomain> (raw)
In-Reply-To: <20211028134918.GB48435@lakrids.cambridge.arm.com>

On 28.10.2021 14:49, Mark Rutland wrote:
>On Wed, Oct 27, 2021 at 06:33:22PM -0700, Pawan Gupta wrote:
>> Borrow CONFIG_CPU_SPECTRE from ARM to be available for all
>> architectures. This will help in configuration of features that depend
>> on CPU being affected by spectre class of vulnerabilities.
>>
>> Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
>
>Given that spectre isn't one specific issue, biut rather a blanket term
>for a bunch of things that can have variable overlap, I don't think this
>makes much sense unless we're going to add finer-grained options for all
>the variants, and IMO it'd make more sene for the architectures to
>directly select the things that'd otherwise be dependent on this.

Isn't ARM already using CPU_SPECTRE for selecting things: 

	config HARDEN_BRANCH_PREDICTOR
	     bool "Harden the branch predictor against aliasing attacks" if EXPERT
	     depends on CPU_SPECTRE

This was the whole motivation for doing the same for x86.

Adding a condition for all architectures is also okay, but its going to
a little messier:

	 config BPF_UNPRIV_DEFAULT_OFF
	        default y if X86 || ARM || ... 

This approach would make sense if architectures wants to explicitly
select the defaults irrespective of architecture being affected by
spectre.

If that's the case I will change the BPF_UNPRIV_DEFAULT_OFF default to
depend on architecture. I hope BPF maintainer, Daniel is okay with it?

Pawan

Added BPF maintainers and bpf@vger to cc.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2021-10-28 19:34 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-28  1:32 [PATCH ebpf v2 0/2] Unprivileged BPF default Pawan Gupta
2021-10-28  1:33 ` [PATCH v2 1/2] arch/Kconfig: Make CONFIG_CPU_SPECTRE available for all architectures Pawan Gupta
2021-10-28  1:33   ` Pawan Gupta
2021-10-28  5:27   ` Greg KH
2021-10-28  5:27     ` Greg KH
2021-10-28 13:49   ` Mark Rutland
2021-10-28 13:49     ` Mark Rutland
2021-10-28 19:36     ` Pawan Gupta [this message]
2021-10-28 19:36       ` Pawan Gupta
2021-10-29  9:22       ` Mark Rutland
2021-10-29  9:22         ` Mark Rutland
2021-10-29 16:05         ` Daniel Borkmann
2021-10-29 16:05           ` Daniel Borkmann
2021-10-29 19:15           ` Pawan Gupta
2021-10-29 19:15             ` Pawan Gupta
2021-10-29 10:08       ` Russell King (Oracle)
2021-10-29 10:08         ` Russell King (Oracle)
2021-10-29 22:51         ` Pawan Gupta
2021-10-29 22:51           ` Pawan Gupta
2021-10-28  1:35 ` [PATCH ebpf v2 2/2] bpf: Make unprivileged bpf depend on CONFIG_CPU_SPECTRE Pawan Gupta
2021-10-28  5:34   ` Greg KH
2021-10-28 19:38     ` Pawan Gupta
2021-10-28 13:57   ` Mark Rutland
2021-10-28 16:44     ` Greg KH

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