From nobody Mon Feb 9 17:22:57 2026 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 4A7631F5FD for ; Wed, 27 Nov 2024 19:04:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732734245; cv=none; b=nuUIZuHgF0gB7mkNFsiuLhVWCpe9+qbBqx9m9/b/QHSI3XS9Y2/ClRnJqjtKr7SgWcqyypUOfoPa4axkdCbrB5nJLUyAZAC2+Muhsnc6FDdDakKDtJZm9zgudSMXRf8bKy5MfxNqjMdY5ZKbpzirJFyBgyWuydw/lCt4ng9HM9Y= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732734245; c=relaxed/simple; bh=Jszb8KFN5GzjUkCQ/IcBcaFlVglAOixLKBZmKX8ltN8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=sv922MtpFJSfiLahRmbEZTBxhV4ZKvz8pBIAKLL4FhKqQBDE4aWYXqrI4XLPtj3qO2uzs8+Yv4AQ23KtTWXKRj0a+zZaSBsQ+uuDouT3QAT931PfLIwbs6VGiPX9PuO6xbbcxG2BYwk33Ss9+ORXvP3JibE1v5I0mM5+7TfKsBo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=desiato.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=ah2JlbFU; arc=none smtp.client-ip=90.155.92.199 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=desiato.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="ah2JlbFU" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; 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=AbThuJMqNCEqi5OCJ2hHO8LahRmj/ISCryb2ADbdx9M=; b=ah2JlbFUdHK5RQ1AnFOXYqBoiM tXKSBRgBzcq16hLM8IfYjNoRPIMC90FYEnffspwc3822yDnFXeAP8s7HfB90kVpEgg1Wr3VSX+hGC W7qZZPUcbEuGr1HoATjsjOT3fy/ppfYZk97D4+Xcc0cJ6AjeRxctXO/5zTxHwGEcRb9g37BWk5xjk pA9NnhXAR0SLiT0Y/SveMSlviSlpvRnxTFhjLft2fBR+KmrKJxPl2BiBJxOh9llUCmOTaWWSAEKnz +Rriu2nSpH4Fy+Uiu+7BwV/eRZalbMkyiC1MFOSpzDDsagkWf8LKrsX9D827x/15pxM/1gpL11FV4 b9H90kWg==; Received: from [2001:8b0:10b:1::ebe] (helo=i7.infradead.org) by desiato.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tGNKF-00000001Sud-188j; Wed, 27 Nov 2024 19:03:47 +0000 Received: from dwoodhou by i7.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tGNKD-00000000BiM-47rP; Wed, 27 Nov 2024 19:03:46 +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, bsz@amazon.de Subject: [RFC PATCH v4 04/20] x86/kexec: Only swap pages for preserve_context mode Date: Wed, 27 Nov 2024 19:00:18 +0000 Message-ID: <20241127190343.44916-5-dwmw2@infradead.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241127190343.44916-1-dwmw2@infradead.org> References: <20241127190343.44916-1-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 desiato.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 fea650f92606..50cc33f2ecb7 100644 --- a/arch/x86/kernel/relocate_kernel_64.S +++ b/arch/x86/kernel/relocate_kernel_64.S @@ -310,6 +310,9 @@ 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 */ + jz .Lnoswap + /* copy source page to swap page */ movq %r10, %rdi movl $512, %ecx @@ -324,6 +327,7 @@ 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