From nobody Tue Feb 10 09:22:17 2026 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.10]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C33041EB5F8; Mon, 9 Feb 2026 07:25:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.10 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770621930; cv=none; b=LweVAELDxR62+/uCqO2F8Bn/K7CGSUySX4TZRL2v+1hqcBxZCLflLUvZmqXCXDtnr8ahNFMmpJ+T5LHfbghPtJ3cyMe/cJAdQYQo6UbskDp7kyNCq336Wp9P5sY/15DiJpHGsCf5aYi81CZcs5MNf2x+3dO0m/P0qYMj9lcRVvw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770621930; c=relaxed/simple; bh=FxXIF/UDFwdpUEz9aVfYkf18vVCta1TtH/HcMsU+WAk=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=XmEYsWUQBxx1iwCWHn374znlLNl/XoG8oUDkH1g4I1P6Fbr92uJZi4xMe9WLxEO3m+i/QV72DQXs3X8GQ/JMZKdafeHMSg2S33erEHInhigmsZ+qAHRdIHHxcLR6aLxeA0AW8ajdmVFO7VNvFtqJwXFqgk6O13GOIm3K/f3JvV8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=EKnZxx9p; arc=none smtp.client-ip=192.198.163.10 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="EKnZxx9p" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1770621930; x=1802157930; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=FxXIF/UDFwdpUEz9aVfYkf18vVCta1TtH/HcMsU+WAk=; b=EKnZxx9pqS0zXNzKIdKa4DBfFDrpXKHwpluMzjXDpfJR7osd9qwW9esN qF9IlhQICs0V7fMEaSJqvvQPd2mP8ubLyKpzvVGo34OIIQYl0lVwoXV8V uaVPSIW1KCK12ujrO7nUgDMBhekstYjuDpUORiPTJxv+qNOsoNbtIzwtw zgkmQeDlV+f6q2dqedLoMk0Tn1yhxBq7CzKdMRk8gn0EoAXZUcRuWpuWc PN383dJV/Kp/iblO+e+1Hie0NfU3wWth+90wzY/HtU3/0pUPUTOO4VQ4w ucLYySjIJvkEjleQs1By83Cn+ZSBAHB39I1Ca+77PtCBXgt4ml7Pq2p+0 g==; X-CSE-ConnectionGUID: vxToSYPKQCiIg1LG9AaB4Q== X-CSE-MsgGUID: Qf9rq95DThSjGPoO6k5r6A== X-IronPort-AV: E=McAfee;i="6800,10657,11695"; a="83098342" X-IronPort-AV: E=Sophos;i="6.21,281,1763452800"; d="scan'208";a="83098342" Received: from fmviesa001.fm.intel.com ([10.60.135.141]) by fmvoesa104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Feb 2026 23:25:30 -0800 X-CSE-ConnectionGUID: SHjNoBXiT1GBuF2eVL0UVw== X-CSE-MsgGUID: o6bquAC/RqGyjivp2nEP6w== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.21,281,1763452800"; d="scan'208";a="241694634" Received: from spr.sh.intel.com ([10.112.229.196]) by fmviesa001.fm.intel.com with ESMTP; 08 Feb 2026 23:25:25 -0800 From: Dapeng Mi To: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Thomas Gleixner , Dave Hansen , Ian Rogers , Adrian Hunter , Jiri Olsa , Alexander Shishkin , Andi Kleen , Eranian Stephane Cc: Mark Rutland , broonie@kernel.org, Ravi Bangoria , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Zide Chen , Falcon Thomas , Dapeng Mi , Xudong Hao , Dapeng Mi Subject: [Patch v6 08/22] x86/fpu: Ensure TIF_NEED_FPU_LOAD is set after saving FPU state Date: Mon, 9 Feb 2026 15:20:33 +0800 Message-Id: <20260209072047.2180332-9-dapeng1.mi@linux.intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260209072047.2180332-1-dapeng1.mi@linux.intel.com> References: <20260209072047.2180332-1-dapeng1.mi@linux.intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Ensure that the TIF_NEED_FPU_LOAD flag is always set after saving the FPU state. This guarantees that the user space FPU state has been saved whenever the TIF_NEED_FPU_LOAD flag is set. A subsequent patch will verify if the user space FPU state can be retrieved from the saved task FPU state in the NMI context by checking the TIF_NEED_FPU_LOAD flag. Suggested-by: Peter Zijlstra Suggested-by: Dave Hansen Signed-off-by: Dapeng Mi --- v6: new patch. arch/x86/include/asm/fpu/sched.h | 2 +- arch/x86/kernel/fpu/core.c | 12 ++++++++---- 2 files changed, 9 insertions(+), 5 deletions(-) diff --git a/arch/x86/include/asm/fpu/sched.h b/arch/x86/include/asm/fpu/sc= hed.h index 89004f4ca208..2d57a7bf5406 100644 --- a/arch/x86/include/asm/fpu/sched.h +++ b/arch/x86/include/asm/fpu/sched.h @@ -36,8 +36,8 @@ static inline void switch_fpu(struct task_struct *old, in= t cpu) !(old->flags & (PF_KTHREAD | PF_USER_WORKER))) { struct fpu *old_fpu =3D x86_task_fpu(old); =20 - set_tsk_thread_flag(old, TIF_NEED_FPU_LOAD); save_fpregs_to_fpstate(old_fpu); + set_tsk_thread_flag(old, TIF_NEED_FPU_LOAD); /* * The save operation preserved register state, so the * fpu_fpregs_owner_ctx is still @old_fpu. Store the diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index da233f20ae6f..0f91a0d7e799 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -359,18 +359,22 @@ int fpu_swap_kvm_fpstate(struct fpu_guest *guest_fpu,= bool enter_guest) struct fpstate *cur_fps =3D fpu->fpstate; =20 fpregs_lock(); - if (!cur_fps->is_confidential && !test_thread_flag(TIF_NEED_FPU_LOAD)) + if (!cur_fps->is_confidential && !test_thread_flag(TIF_NEED_FPU_LOAD)) { save_fpregs_to_fpstate(fpu); + set_thread_flag(TIF_NEED_FPU_LOAD); + } =20 /* Swap fpstate */ if (enter_guest) { - fpu->__task_fpstate =3D cur_fps; + WRITE_ONCE(fpu->__task_fpstate, cur_fps); + barrier(); fpu->fpstate =3D guest_fps; guest_fps->in_use =3D true; } else { guest_fps->in_use =3D false; fpu->fpstate =3D fpu->__task_fpstate; - fpu->__task_fpstate =3D NULL; + barrier(); + WRITE_ONCE(fpu->__task_fpstate, NULL); } =20 cur_fps =3D fpu->fpstate; @@ -456,8 +460,8 @@ void kernel_fpu_begin_mask(unsigned int kfpu_mask) =20 if (!(current->flags & (PF_KTHREAD | PF_USER_WORKER)) && !test_thread_flag(TIF_NEED_FPU_LOAD)) { - set_thread_flag(TIF_NEED_FPU_LOAD); save_fpregs_to_fpstate(x86_task_fpu(current)); + set_thread_flag(TIF_NEED_FPU_LOAD); } __cpu_invalidate_fpregs_state(); =20 --=20 2.34.1