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From:   Thomas Gleixner <tglx@linutronix.de>
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To:     ira.weiny@intel.com, Dave Hansen <dave.hansen@linux.intel.com>,
        Dan Williams <dan.j.williams@intel.com>
Cc:     Ira Weiny <ira.weiny@intel.com>, Fenghua Yu <fenghua.yu@intel.com>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Andy Lutomirski <luto@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Rick Edgecombe <rick.p.edgecombe@intel.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org, nvdimm@lists.linux.dev,
        linux-mm@kvack.org
Subject: Re: [PATCH V7 07/18] x86/pks: Preserve the PKRS MSR on context switch
In-Reply-To: <20210804043231.2655537-8-ira.weiny@intel.com>
References: <20210804043231.2655537-1-ira.weiny@intel.com>
 <20210804043231.2655537-8-ira.weiny@intel.com>
Date:   Thu, 25 Nov 2021 16:25:32 +0100
Message-ID: <87fsrkl0k3.ffs@tglx>
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On Tue, Aug 03 2021 at 21:32, ira weiny wrote:
> @@ -658,6 +659,8 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
>  	/* Load the Intel cache allocation PQR MSR. */
>  	resctrl_sched_in();
>  
> +	pkrs_write_current();

This is invoked from switch_to() and does this extra get/put_cpu_ptr()
dance in the write function for no reason. Can you please stop sticking
overhead into the hotpath just because?

Thanks,

        tglx