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Message-ID: <758089a4-52d5-4649-8aee-89e60044918a@intel.com>
Date: Thu, 9 May 2024 11:41:23 -0700
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH v2 1/2] x86/fpu: Extend kernel_fpu_begin_mask() to
 initialize AMX state
To: Dave Hansen <dave.hansen@intel.com>, <linux-kernel@vger.kernel.org>
CC: <x86@kernel.org>, <platform-driver-x86@vger.kernel.org>,
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	<ilpo.jarvinen@linux.intel.com>, <tony.luck@intel.com>,
	<ashok.raj@intel.com>, <jithu.joseph@intel.com>
References: <20240430212508.105117-1-chang.seok.bae@intel.com>
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From: "Chang S. Bae" <chang.seok.bae@intel.com>
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On 5/9/2024 10:36 AM, Dave Hansen wrote:
> 
> I'd probably just do this:
> 
> +	kernel_fpu_begin();
> +	// AMX *MUST* be in the init state for the wrmsr() to work.
> +	// But, the more in the init state, the less state the test
> +	// has to save and restore.  Just zap everything.
> +	restore_fpregs_from_fpstate(&init_fpstate,	
> +				    fpu_user_cfg.max_features);
> +

I assume that this snippet goes to the IFS driver side. Then, we need to 
introduce and export a new wrapper for this. 
restore_fpregs_from_fpstate() and its arguments are not accessible as of 
now.

Also, I think we should encapsulate them. If we follow this style, we 
could have invoked tilerelease() directly from the idle driver, right?

>          wrmsrl(MSR_ACTIVATE_SCAN, params->activate->data);
>          rdmsrl(MSR_SCAN_STATUS, status.data);
> 
> +	kernel_fpu_end();