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From:   Thomas Gleixner <tglx@linutronix.de>
To:     "Luck\, Tony" <tony.luck@intel.com>,
        Xiaoyao Li <xiaoyao.li@intel.com>
Cc:     Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
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Subject: Re: [PATCH v5 2/9] x86/split_lock: Avoid runtime reads of the TEST_CTRL MSR
In-Reply-To: <20200321004315.GB6578@agluck-desk2.amr.corp.intel.com>
References: <20200315050517.127446-1-xiaoyao.li@intel.com> <20200315050517.127446-3-xiaoyao.li@intel.com> <20200321004315.GB6578@agluck-desk2.amr.corp.intel.com>
Date:   Mon, 23 Mar 2020 18:06:31 +0100
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"Luck, Tony" <tony.luck@intel.com> writes:

> On Sun, Mar 15, 2020 at 01:05:10PM +0800, Xiaoyao Li wrote:
>> In a context switch from a task that is detecting split locks
>> to one that is not (or vice versa) we need to update the TEST_CTRL
>> MSR. Currently this is done with the common sequence:
>> 	read the MSR
>> 	flip the bit
>> 	write the MSR
>> in order to avoid changing the value of any reserved bits in the MSR.
>> 
>> Cache the value of the TEST_CTRL MSR when we read it during initialization
>> so we can avoid an expensive RDMSR instruction during context switch.
>> 
>> Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
>> Originally-by: Tony Luck <tony.luck@intel.com>
>> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
>
> Is it bad form to Ack/Review patches originally by oneself?

Only if they are broken ....