From nobody Sun Feb 8 21:26:38 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 ACBA21991BF for ; Mon, 27 Jan 2025 22:46:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738017985; cv=none; b=napJc80bnAI+fNUMp8A7PEgyJuOMpVmR3qgamFASrBc8Eb0+yPLKlPlHGOWjLdQ4S6szrZCS5Fj2tEH8ZhbIZG8cNnS0dSdTSa6YfcIM8FJgZFieh/AnJfIm3Wf44fdpWvrMZTPMs/qKFUylsB7VRJ6YDI4sn5wHhpUhXfLHKJY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738017985; c=relaxed/simple; bh=PSaW/xnatsf1HWtwdGJFNxHy3YTHBYQYsv9kIzj+TWQ=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=UPr2llXbC/aS1R0pqRsrxPhroy1cCv1aSWivrDfyKIY8K5w+mvuHKbg6d3Igxueio6jaxC8tbcx89vCj5B+EszQNS3NcViRA5dVvLoENAhZDg2oymwZcAGv1d1sPM9EwGVCIcSx2PHlldNNCOPqDS73iMV1KCAkeSp2mkIzFf4I= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KwFdiltu; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KwFdiltu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E782DC4CED2; Mon, 27 Jan 2025 22:46:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1738017985; bh=PSaW/xnatsf1HWtwdGJFNxHy3YTHBYQYsv9kIzj+TWQ=; h=From:To:Cc:Subject:Date:From; b=KwFdiltuXVoWfp7NEqP13xCmMiKpVwQygq7ouO3bAyVsKtxeYWFgnO1QREkpkZE7O 1JzAHQ/mrLIlB0EGS5nHqiHuN29WphyMsSjX1/YBbefaayOlxu53UQW50CW73pXTMx mDkmL36SEDLFwcwgdtBQfFHbohk1KoyQL/IOh74OYQ4hqYoDqPSuvDVmdeAa/Yc+eL NCYpMN+nCNvvhm3rFNnr+TktgT/R42115hXezLwdg4NAVCaBjnaMXKnfL0HNHKY4aJ Gu+BjKmNe+LPK8PLYDxKvW1qgKiiq6n55TM2PhAWkID+qDeISYsXoApD+sn78SYEeG FPFSyguGjlnIQ== From: Eric Biggers To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H . Peter Anvin" , Sean Christopherson Subject: [PATCH v2] x86/fpu: make WARN_ON_FPU get fully optimized out Date: Mon, 27 Jan 2025 14:45:23 -0800 Message-ID: <20250127224523.94300-1-ebiggers@kernel.org> X-Mailer: git-send-email 2.48.1 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" From: Eric Biggers Currently WARN_ON_FPU evaluates its argument even if CONFIG_X86_DEBUG_FPU is disabled, which adds unnecessary instructions to several functions, for example kernel_fpu_begin(). Fix this by using BUILD_BUG_ON_INVALID(x) in the no-debug case rather than (void)(x). Fixes: 83242c515881 ("x86/fpu: Make WARN_ON_FPU() more robust in the !CONFI= G_X86_DEBUG_FPU case") Suggested-by: Sean Christopherson Signed-off-by: Eric Biggers --- v2: use BUILD_BUG_ON_INVALID() as suggested by Sean Christopherson. arch/x86/kernel/fpu/internal.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/fpu/internal.h b/arch/x86/kernel/fpu/internal.h index dbdb31f55fc7f..975de070c9c98 100644 --- a/arch/x86/kernel/fpu/internal.h +++ b/arch/x86/kernel/fpu/internal.h @@ -16,11 +16,11 @@ static __always_inline __pure bool use_fxsr(void) } =20 #ifdef CONFIG_X86_DEBUG_FPU # define WARN_ON_FPU(x) WARN_ON_ONCE(x) #else -# define WARN_ON_FPU(x) ({ (void)(x); 0; }) +# define WARN_ON_FPU(x) ({ BUILD_BUG_ON_INVALID(x); 0; }) #endif =20 /* Used in init.c */ extern void fpstate_init_user(struct fpstate *fpstate); extern void fpstate_reset(struct fpu *fpu); base-commit: 805ba04cb7ccfc7d72e834ebd796e043142156ba --=20 2.48.1