From nobody Tue Feb 10 01:58:48 2026 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 ECCA618A6A9 for ; Fri, 22 Nov 2024 22:47:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732315665; cv=none; b=iAhU+N7i/t281xnJnR9H1pr9hmdgxz6qGu6yyTWUih6ocQWusP/KCA3Bt5OmjMjNXDPdGuv8Ig4gtpd47Nm5q+QDLp5xPdBDtVxz88oAA03DEuU6XwjJMU21P4eUl56tC0/voSTHDlLfP8Z5Kfj1i0uN9alrYkLNzvPC8/I9SJ4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732315665; c=relaxed/simple; bh=PsmoAGl847a9zQLItcMGgTXPyTmUHqs5pQtbYpPJSqo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=nU+7R18Xo6Y5jkGBwsV57vxBUglAkMnhf80hb/oxERPDhU8g/KdySo1GWkQ90K1iMv+xBY5mSsswfXnX7ZWSyBYjHeSANyM7galdhnaoLm1JHqJ4jxQ3T0ui8QWA0u+g8UGqEWVXpB4c9PAuZsumX3sxctaYW1QCX3HhQMLaZvs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=casper.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=jCMm6BNV; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=casper.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="jCMm6BNV" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Sender:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description; bh=S0QVtAVD7M7pFpqYQRYpOlRlIpsQlWjl3XEa+4AG3hg=; b=jCMm6BNVrfGOtot4P6MWH5QfVr Jaa98yGLe9SXtDBP7HNJm6Bj4EXEkUldoFDGZMjV2WsTkMKvcq0gEHh0kHy21FKLqaw7eb+munQpl 9w74HhVDAg4eQ7bZIWrVhQB+i6StbGjDlrAcusy/A22QCVNYoMQvD6UN40lqeyLXZnqNPRjhgsg3g OkmpX88v3OdYPkk6JkOqugHeJ41SGbOUeNxH5HV6XD5SlUUvtoTeDtXVDP/WyDDgpUe8+AHvklQQK /dgiDEx+D7xjXKej74Nk/9ZwPiJZic6d+rNmOWfVbTGXt/2uXS2v3KFnIvnKR5stFjjLb/Uu2CLXq LC7y+aYQ==; Received: from [2001:8b0:10b:1::ebe] (helo=i7.infradead.org) by casper.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tEcQp-00000008PHS-2CWY; Fri, 22 Nov 2024 22:47:20 +0000 Received: from dwoodhou by i7.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tEcQp-00000000iiC-034R; Fri, 22 Nov 2024 22:47:19 +0000 From: David Woodhouse To: kexec@lists.infradead.org Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , David Woodhouse , "Kirill A. Shutemov" , Kai Huang , Nikolay Borisov , linux-kernel@vger.kernel.org, Simon Horman , Dave Young , Peter Zijlstra , jpoimboe@kernel.org Subject: [RFC PATCH v2 04/16] x86/kexec: Only swap pages for preserve_context mode Date: Fri, 22 Nov 2024 22:38:13 +0000 Message-ID: <20241122224715.171751-5-dwmw2@infradead.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241122224715.171751-1-dwmw2@infradead.org> References: <20241122224715.171751-1-dwmw2@infradead.org> 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 Sender: David Woodhouse X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html Content-Type: text/plain; charset="utf-8" From: David Woodhouse There's no need to swap pages (which involves three memcopies for each page) in the plain kexec case. Just do a single copy from source to destination page. Signed-off-by: David Woodhouse --- arch/x86/kernel/relocate_kernel_64.S | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocat= e_kernel_64.S index ed2ae50535dd..92d5dbed3097 100644 --- a/arch/x86/kernel/relocate_kernel_64.S +++ b/arch/x86/kernel/relocate_kernel_64.S @@ -308,6 +308,9 @@ SYM_CODE_START_LOCAL_NOALIGN(swap_pages) movq %rdi, %rdx /* Save destination page to %rdx */ movq %rsi, %rax /* Save source page to %rax */ =20 + testq %r11, %r11 /* Only actually swap for preserve_context */ + jnz .Lnoswap + /* copy source page to swap page */ movq %r10, %rdi movl $512, %ecx @@ -322,6 +325,7 @@ SYM_CODE_START_LOCAL_NOALIGN(swap_pages) /* copy swap page to destination page */ movq %rdx, %rdi movq %r10, %rsi +.Lnoswap: movl $512, %ecx rep ; movsq =20 --=20 2.47.0