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From: Dave Hansen <dave.hansen@intel.com>
To: Kohei Tarumizu <tarumizu.kohei@fujitsu.com>,
	catalin.marinas@arm.com, will@kernel.org, tglx@linutronix.de,
	mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com,
	x86@kernel.org, hpa@zytor.com,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, fenghua.yu@intel.com,
	reinette.chatre@intel.com
Subject: Re: [PATCH v3 6/9] x86: resctrl: pseudo_lock: Fix to restore to original value when re-enabling hardware prefetch register
Date: Wed, 20 Apr 2022 13:56:07 -0700	[thread overview]
Message-ID: <2eb705cd-8607-4b8c-2c0b-31265d503eed@intel.com> (raw)
In-Reply-To: <20220420030223.689259-7-tarumizu.kohei@fujitsu.com>

On 4/19/22 20:02, Kohei Tarumizu wrote:
> The current pseudo_lock.c code overwrittes the value of the
> MSR_MISC_FEATURE_CONTROL to 0 even if the original value is not 0.
> Therefore, modify it to save and restore the original values.

It would be nice to mention that the wrmsr()'s in this patch are only
done inside of an interrupt-disabled region.  Without that little tidbit
of information, it's not obviously correct that the smp_call_function()
in patch 8/9 is correct.

The x86 code here looks reasonable otherwise.  It's a little bit of a
shame that this is *ONLY* for BROADWELL_X for now, but I assume you were
just conservative about it because that's all you have to test on.

WARNING: multiple messages have this Message-ID (diff)
From: Dave Hansen <dave.hansen@intel.com>
To: Kohei Tarumizu <tarumizu.kohei@fujitsu.com>,
	catalin.marinas@arm.com, will@kernel.org, tglx@linutronix.de,
	mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com,
	x86@kernel.org, hpa@zytor.com,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, fenghua.yu@intel.com,
	reinette.chatre@intel.com
Subject: Re: [PATCH v3 6/9] x86: resctrl: pseudo_lock: Fix to restore to original value when re-enabling hardware prefetch register
Date: Wed, 20 Apr 2022 13:56:07 -0700	[thread overview]
Message-ID: <2eb705cd-8607-4b8c-2c0b-31265d503eed@intel.com> (raw)
In-Reply-To: <20220420030223.689259-7-tarumizu.kohei@fujitsu.com>

On 4/19/22 20:02, Kohei Tarumizu wrote:
> The current pseudo_lock.c code overwrittes the value of the
> MSR_MISC_FEATURE_CONTROL to 0 even if the original value is not 0.
> Therefore, modify it to save and restore the original values.

It would be nice to mention that the wrmsr()'s in this patch are only
done inside of an interrupt-disabled region.  Without that little tidbit
of information, it's not obviously correct that the smp_call_function()
in patch 8/9 is correct.

The x86 code here looks reasonable otherwise.  It's a little bit of a
shame that this is *ONLY* for BROADWELL_X for now, but I assume you were
just conservative about it because that's all you have to test on.

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  reply	other threads:[~2022-04-20 20:56 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-20  3:02 [PATCH v3 0/9] Add hardware prefetch control driver for A64FX and x86 Kohei Tarumizu
2022-04-20  3:02 ` Kohei Tarumizu
2022-04-20  3:02 ` [PATCH v3 1/9] drivers: base: Add hardware prefetch control core driver Kohei Tarumizu
2022-04-20  3:02   ` Kohei Tarumizu
2022-04-20 21:40   ` Thomas Gleixner
2022-04-20 21:40     ` Thomas Gleixner
2022-04-22 12:10     ` tarumizu.kohei
2022-04-22 12:10       ` tarumizu.kohei
2022-04-21  6:18   ` Greg KH
2022-04-21  6:18     ` Greg KH
2022-04-22 12:30     ` tarumizu.kohei
2022-04-22 12:30       ` tarumizu.kohei
2022-04-20  3:02 ` [PATCH v3 2/9] drivers: base: Add Kconfig/Makefile to build " Kohei Tarumizu
2022-04-20  3:02   ` Kohei Tarumizu
2022-04-20  3:02 ` [PATCH v3 3/9] soc: fujitsu: Add hardware prefetch control support for A64FX Kohei Tarumizu
2022-04-20  3:02   ` Kohei Tarumizu
2022-04-20  3:02 ` [PATCH v3 4/9] soc: fujitsu: Add Kconfig/Makefile to build hardware prefetch control driver Kohei Tarumizu
2022-04-20  3:02   ` Kohei Tarumizu
2022-04-20 22:14   ` Thomas Gleixner
2022-04-20 22:14     ` Thomas Gleixner
2022-04-20  3:02 ` [PATCH v3 5/9] arm64: Create cache sysfs directory without ACPI PPTT for hardware prefetch control Kohei Tarumizu
2022-04-20  3:02   ` Kohei Tarumizu
2022-04-20  3:02 ` [PATCH v3 6/9] x86: resctrl: pseudo_lock: Fix to restore to original value when re-enabling hardware prefetch register Kohei Tarumizu
2022-04-20  3:02   ` Kohei Tarumizu
2022-04-20 20:56   ` Dave Hansen [this message]
2022-04-20 20:56     ` Dave Hansen
2022-04-22 12:01     ` tarumizu.kohei
2022-04-22 12:01       ` tarumizu.kohei
2022-04-25 23:17   ` Reinette Chatre
2022-04-25 23:17     ` Reinette Chatre
2022-04-27  2:51     ` tarumizu.kohei
2022-04-27  2:51       ` tarumizu.kohei
2022-04-20  3:02 ` [PATCH v3 7/9] x86: Add hardware prefetch control support for x86 Kohei Tarumizu
2022-04-20  3:02   ` Kohei Tarumizu
2022-04-20 22:27   ` Thomas Gleixner
2022-04-20 22:27     ` Thomas Gleixner
2022-04-22 12:16     ` tarumizu.kohei
2022-04-22 12:16       ` tarumizu.kohei
2022-04-20  3:02 ` [PATCH v3 8/9] x86: Add Kconfig/Makefile to build hardware prefetch control driver Kohei Tarumizu
2022-04-20  3:02   ` Kohei Tarumizu
2022-04-20  3:02 ` [PATCH v3 9/9] docs: ABI: Add sysfs documentation interface of " Kohei Tarumizu
2022-04-20  3:02   ` Kohei Tarumizu

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