linux-kernel - Re: [PATCH v2 2/2] platform/x86/intel/ifs: Initialize AMX state for the scan test

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Date: Tue, 7 May 2024 17:19:07 -0700
From: Ashok Raj <ashok.raj@...el.com>
To: "Chang S. Bae" <chang.seok.bae@...el.com>
CC: <linux-kernel@...r.kernel.org>, <x86@...nel.org>,
	<platform-driver-x86@...r.kernel.org>, <tglx@...utronix.de>,
	<mingo@...hat.com>, <bp@...en8.de>, <dave.hansen@...ux.intel.com>,
	<hdegoede@...hat.com>, <ilpo.jarvinen@...ux.intel.com>,
	<tony.luck@...el.com>, <jithu.joseph@...el.com>, Ashok Raj
	<ashok.raj@...el.com>
Subject: Re: [PATCH v2 2/2] platform/x86/intel/ifs: Initialize AMX state for
 the scan test

On Tue, May 07, 2024 at 04:53:44PM -0700, Bae, Chang Seok wrote:
> In-Field Scan aborts if AMX state is not in initialized state. Use
> kernel_fpu_begin_mask(KFPU_AMX) to ensure AMX state is initialized.
> 
> Introduce custom FPU handling wrappers to ensure compliance with the
> established FPU API semantics. This change follows the EFI case from
> commit b0dc553cfc9d ("x86/fpu: Make the EFI FPU calling convention
> explicit").
> 
> Then, use these wrappers to surround the MSR_ACTIVATE_SCAN write to
> minimize the critical section. To prevent unnecessary delays, invoke
> ifs_fpu_begin() before entering the rendezvous loop.
> 
> Signed-off-by: Chang S. Bae <chang.seok.bae@...el.com>
> Reviewed-by: Jithu Joseph <jithu.joseph@...el.com>
> Tested-by: Jithu Joseph <jithu.joseph@...el.com>
> Acked-by: Hans de Goede <hdegoede@...hat.com>

Reviewed-by: Ashok Raj <ashok.raj@...el.com>

for both patches.