From nobody Tue Nov 26 20:26:55 2024 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass(p=none dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1705375348; cv=none; d=zohomail.com; s=zohoarc; b=HSoicrqI/jKj+UnTJDtp9esSfxh/id+Umm8B+5WYCpOjjaaCR1C6Y7616gAajybSeEKK7kk70i8M4sAkGdnV8uLxGRj3uuxUYkJA6ttdcHjkNsji5qAE3sODGKrqmsBvw1AwNe6PgX0tfVgEeIPYUxq1OIW/wXQ/WLt7FNymh9I= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1705375348; h=Content-Type:Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:Subject:To:To:Message-Id:Reply-To; bh=zaWAr7R+o0BFfn2GI+58asPDPgLyrb90Op/REHjc/j8=; b=Q48GgSITYToHbwUc9f66R9Ac1devj1PiUmQzrKlym9A1SR5HWdzgbC21gW8fIXC75whvj/AdCbGfZfb+4pzQe+Tl5esJwYbNKSDU9ovwOMfoXwH+lC+ffJFSqP/81E5+a0z/F8tz796Anfj7gjOSRmaJKk5iOi/kD05R4vb6UEo= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass header.from= (p=none dis=none) Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1705375348568339.842467083971; Mon, 15 Jan 2024 19:22:28 -0800 (PST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rPa0M-0005rD-Gq; Mon, 15 Jan 2024 22:20:46 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rPa0K-0005mO-MC for qemu-devel@nongnu.org; Mon, 15 Jan 2024 22:20:44 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rPa0I-00036C-Lb for qemu-devel@nongnu.org; Mon, 15 Jan 2024 22:20:44 -0500 Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-591-G9pww0BRNneadZRs_kGSBQ-1; Mon, 15 Jan 2024 22:20:40 -0500 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id BA179185A780; Tue, 16 Jan 2024 03:20:39 +0000 (UTC) Received: from x1n.redhat.com (unknown [10.72.116.92]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6CB153C25; Tue, 16 Jan 2024 03:20:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1705375241; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=zaWAr7R+o0BFfn2GI+58asPDPgLyrb90Op/REHjc/j8=; b=cS5Sb544mXhnmUw4dOCdpkqSglC6cPFyEwgeTpfVh2YKJnyW9ZnILBM+ok7E1/IZVPxVjk 90lzMAOR94Evpo290elY+TNCxTzI/1NysHguFYw7aHKv21alKYETZf0j2y5s7S+hdYT4bu +NXlVCGPkliuF+YulVwbX4OWbnir0ic= X-MC-Unique: G9pww0BRNneadZRs_kGSBQ-1 From: peterx@redhat.com To: qemu-devel@nongnu.org, Peter Maydell Cc: peterx@redhat.com, Fabiano Rosas , =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= Subject: [PULL 14/20] docs/migration: Split "Debugging" and "Firmware" Date: Tue, 16 Jan 2024 11:19:41 +0800 Message-ID: <20240116031947.69017-15-peterx@redhat.com> In-Reply-To: <20240116031947.69017-1-peterx@redhat.com> References: <20240116031947.69017-1-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.1 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.129.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.531, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1705375349911100007 From: Peter Xu Move the two sections into a separate file called "best-practices.rst". Add the entry into index. Reviewed-by: C=C3=A9dric Le Goater Link: https://lore.kernel.org/r/20240109064628.595453-6-peterx@redhat.com Signed-off-by: Peter Xu --- docs/devel/migration/best-practices.rst | 48 +++++++++++++++++++++++++ docs/devel/migration/index.rst | 1 + docs/devel/migration/main.rst | 44 ----------------------- 3 files changed, 49 insertions(+), 44 deletions(-) create mode 100644 docs/devel/migration/best-practices.rst diff --git a/docs/devel/migration/best-practices.rst b/docs/devel/migration= /best-practices.rst new file mode 100644 index 0000000000..d7c34a3014 --- /dev/null +++ b/docs/devel/migration/best-practices.rst @@ -0,0 +1,48 @@ +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D +Best practices +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +Debugging +=3D=3D=3D=3D=3D=3D=3D=3D=3D + +The migration stream can be analyzed thanks to ``scripts/analyze-migration= .py``. + +Example usage: + +.. code-block:: shell + + $ qemu-system-x86_64 -display none -monitor stdio + (qemu) migrate "exec:cat > mig" + (qemu) q + $ ./scripts/analyze-migration.py -f mig + { + "ram (3)": { + "section sizes": { + "pc.ram": "0x0000000008000000", + ... + +See also ``analyze-migration.py -h`` help for more options. + +Firmware +=3D=3D=3D=3D=3D=3D=3D=3D + +Migration migrates the copies of RAM and ROM, and thus when running +on the destination it includes the firmware from the source. Even after +resetting a VM, the old firmware is used. Only once QEMU has been restart= ed +is the new firmware in use. + +- Changes in firmware size can cause changes in the required RAMBlock size + to hold the firmware and thus migration can fail. In practice it's best + to pad firmware images to convenient powers of 2 with plenty of space + for growth. + +- Care should be taken with device emulation code so that newer + emulation code can work with older firmware to allow forward migration. + +- Care should be taken with newer firmware so that backward migration + to older systems with older device emulation code will work. + +In some cases it may be best to tie specific firmware versions to specific +versioned machine types to cut down on the combinations that will need +support. This is also useful when newer versions of firmware outgrow +the padding. diff --git a/docs/devel/migration/index.rst b/docs/devel/migration/index.rst index 7fc02b9520..9a8fd1ead7 100644 --- a/docs/devel/migration/index.rst +++ b/docs/devel/migration/index.rst @@ -11,3 +11,4 @@ QEMU live migration works. compatibility vfio virtio + best-practices diff --git a/docs/devel/migration/main.rst b/docs/devel/migration/main.rst index b3e31bb52f..97811ce371 100644 --- a/docs/devel/migration/main.rst +++ b/docs/devel/migration/main.rst @@ -52,27 +52,6 @@ All these migration protocols use the same infrastructur= e to save/restore state devices. This infrastructure is shared with the savevm/loadvm functionality. =20 -Debugging -=3D=3D=3D=3D=3D=3D=3D=3D=3D - -The migration stream can be analyzed thanks to ``scripts/analyze-migration= .py``. - -Example usage: - -.. code-block:: shell - - $ qemu-system-x86_64 -display none -monitor stdio - (qemu) migrate "exec:cat > mig" - (qemu) q - $ ./scripts/analyze-migration.py -f mig - { - "ram (3)": { - "section sizes": { - "pc.ram": "0x0000000008000000", - ... - -See also ``analyze-migration.py -h`` help for more options. - Common infrastructure =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =20 @@ -970,26 +949,3 @@ the background migration channel. Anyone who cares ab= out latencies of page faults during a postcopy migration should enable this feature. By default, it's not enabled. =20 -Firmware -=3D=3D=3D=3D=3D=3D=3D=3D - -Migration migrates the copies of RAM and ROM, and thus when running -on the destination it includes the firmware from the source. Even after -resetting a VM, the old firmware is used. Only once QEMU has been restart= ed -is the new firmware in use. - -- Changes in firmware size can cause changes in the required RAMBlock size - to hold the firmware and thus migration can fail. In practice it's best - to pad firmware images to convenient powers of 2 with plenty of space - for growth. - -- Care should be taken with device emulation code so that newer - emulation code can work with older firmware to allow forward migration. - -- Care should be taken with newer firmware so that backward migration - to older systems with older device emulation code will work. - -In some cases it may be best to tie specific firmware versions to specific -versioned machine types to cut down on the combinations that will need -support. This is also useful when newer versions of firmware outgrow -the padding. --=20 2.43.0