From patchwork Thu Jan 9 14:09:58 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Fabiano Rosas X-Patchwork-Id: 13932624 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4308FE77197 for ; Thu, 9 Jan 2025 14:14:18 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tVtH1-0005gc-QD; Thu, 09 Jan 2025 09:12:35 -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 1tVtGy-0005fO-8o for qemu-devel@nongnu.org; Thu, 09 Jan 2025 09:12:32 -0500 Received: from smtp-out2.suse.de ([2a07:de40:b251:101:10:150:64:2]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1tVtGl-0000Y4-2I for qemu-devel@nongnu.org; Thu, 09 Jan 2025 09:12:20 -0500 Received: from imap1.dmz-prg2.suse.org (unknown [10.150.64.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id EFF6B1F456; Thu, 9 Jan 2025 14:12:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1736431938; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3erWeuh+rYsh1mrAYu34l7atDaNcjclCzXTMlmloLdQ=; b=Ur6VrKejF3cNmDvfydYOXgv+avGU8Cp4aKM0k4hMdEI3qvdobkgUPawadJAOUQERkiZrpE A/rXV/oHKuIN6dSCsO8VAXHZhuYZ+Wp2juz6JZxh0dRwST8MaZGnU2gjflH/4dBh2JpGyw NVcS1VXLaSjoVIwdo85JNfgzGrCgz2I= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1736431938; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3erWeuh+rYsh1mrAYu34l7atDaNcjclCzXTMlmloLdQ=; b=1MJQ4URn7uCG8PNPYljy9OTXc4U/uWDh5oDJ2o+goenpnKhY+b8Wd7h9QUkFkK/2tKlhIV RRB7UGv8ifbxlDAA== Authentication-Results: smtp-out2.suse.de; none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1736431937; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3erWeuh+rYsh1mrAYu34l7atDaNcjclCzXTMlmloLdQ=; b=MJrw0acUc0+WR/K4KBR47jmLAW7/u3UthNYqdmtGY87LBlbUbsOk9GhyQM7hMP4KwkmzHU vwUGtLTnaFJYItA5UWKct3EPlTjT/Cs1LuVyMqZG4qE89eF0cEexDqKy1UdgacxMBWowjG tmSNCv3PVh4y7Qe3PI/5Ray2MpsYoSU= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1736431937; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3erWeuh+rYsh1mrAYu34l7atDaNcjclCzXTMlmloLdQ=; b=Nhi3qiUb5VcOVUxZ7E2MBZFVNvWlAyQwDEoqvsy6nJ77/sTDiHuObX1YtFff+KqQAGKRfu K63OtTp0aNbNFvAw== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id BFEE313876; Thu, 9 Jan 2025 14:12:16 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 6OnkIEDZf2fOWgAAD6G6ig (envelope-from ); Thu, 09 Jan 2025 14:12:16 +0000 From: Fabiano Rosas To: qemu-devel@nongnu.org Cc: Peter Xu , Thomas Huth Subject: [PATCH v2 6/7] migration: Fix arrays of pointers in JSON writer Date: Thu, 9 Jan 2025 11:09:58 -0300 Message-Id: <20250109140959.19464-7-farosas@suse.de> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20250109140959.19464-1-farosas@suse.de> References: <20250109140959.19464-1-farosas@suse.de> MIME-Version: 1.0 X-Spamd-Result: default: False [-2.80 / 50.00]; BAYES_HAM(-3.00)[100.00%]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_MISSING_CHARSET(0.50)[]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MIME_TRACE(0.00)[0:+]; TO_DN_SOME(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[3]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:mid,suse.de:email,imap1.dmz-prg2.suse.org:helo]; RCVD_TLS_ALL(0.00)[] Received-SPF: pass client-ip=2a07:de40:b251:101:10:150:64:2; envelope-from=farosas@suse.de; helo=smtp-out2.suse.de X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Currently, if an array of pointers contains a NULL pointer, that pointer will be encoded as '0' in the stream. Since the JSON writer doesn't define a "pointer" type, that '0' will now be an uint8, which is different from the original type being pointed to, e.g. struct. (we're further calling uint8 "nullptr", but that's irrelevant to the issue) That mixed-type array shouldn't be compressed, otherwise data is lost as the code currently makes the whole array have the type of the first element: css = {NULL, NULL, ..., 0x5555568a7940, NULL}; {"name": "s390_css", "instance_id": 0, "vmsd_name": "s390_css", "version": 1, "fields": [ ..., {"name": "css", "array_len": 256, "type": "nullptr", "size": 1}, ..., ]} In the above, the valid pointer at position 254 got lost among the compressed array of nullptr. While we could disable the array compression when a NULL pointer is found, the JSON part of the stream still makes part of downtime, so we should avoid writing unecessary bytes to it. Keep the array compression in place, but if NULL and non-NULL pointers are mixed break the array into several type-contiguous pieces : css = {NULL, NULL, ..., 0x5555568a7940, NULL}; {"name": "s390_css", "instance_id": 0, "vmsd_name": "s390_css", "version": 1, "fields": [ ..., {"name": "css", "array_len": 254, "type": "nullptr", "size": 1}, {"name": "css", "type": "struct", "struct": {"vmsd_name": "s390_css_img", ... }, "size": 768}, {"name": "css", "type": "nullptr", "size": 1}, ..., ]} Now each type-discontiguous region will become a new JSON entry. The reader should interpret this as a concatenation of values, all part of the same field. Parsing the JSON with analyze-script.py now shows the proper data being pointed to at the places where the pointer is valid and "nullptr" where there's NULL: "s390_css (14)": { ... "css": [ "nullptr", "nullptr", ... "nullptr", { "chpids": [ { "in_use": "0x00", "type": "0x00", "is_virtual": "0x00" }, ... ] }, "nullptr", } Signed-off-by: Fabiano Rosas --- migration/vmstate.c | 33 ++++++++++++++++++++++++++++++++- scripts/analyze-migration.py | 29 +++++++++++++++++++++-------- 2 files changed, 53 insertions(+), 9 deletions(-) diff --git a/migration/vmstate.c b/migration/vmstate.c index 52704c822c..a79ccf3875 100644 --- a/migration/vmstate.c +++ b/migration/vmstate.c @@ -425,15 +425,19 @@ int vmstate_save_state_v(QEMUFile *f, const VMStateDescription *vmsd, int size = vmstate_size(opaque, field); uint64_t old_offset, written_bytes; JSONWriter *vmdesc_loop = vmdesc; + bool is_prev_null = false; trace_vmstate_save_state_loop(vmsd->name, field->name, n_elems); if (field->flags & VMS_POINTER) { first_elem = *(void **)first_elem; assert(first_elem || !n_elems || !size); } + for (i = 0; i < n_elems; i++) { void *curr_elem = first_elem + size * i; const VMStateField *inner_field; + bool is_null; + int max_elems = n_elems - i; old_offset = qemu_file_transferred(f); if (field->flags & VMS_ARRAY_OF_POINTER) { @@ -448,12 +452,39 @@ int vmstate_save_state_v(QEMUFile *f, const VMStateDescription *vmsd, * not follow. */ inner_field = vmsd_create_fake_nullptr_field(field); + is_null = true; } else { inner_field = field; + is_null = false; + } + + /* + * Due to the fake nullptr handling above, if there's mixed + * null/non-null data, it doesn't make sense to emit a + * compressed array representation spanning the entire array + * because the field types will be different (e.g. struct + * vs. uint64_t). Search ahead for the next null/non-null + * element and start a new compressed array if found. + */ + if (field->flags & VMS_ARRAY_OF_POINTER && + is_null != is_prev_null) { + + is_prev_null = is_null; + vmdesc_loop = vmdesc; + + for (int j = i + 1; j < n_elems; j++) { + void *elem = *(void **)(first_elem + size * j); + bool elem_is_null = !elem && size; + + if (is_null != elem_is_null) { + max_elems = j - i; + break; + } + } } vmsd_desc_field_start(vmsd, vmdesc_loop, inner_field, - i, n_elems); + i, max_elems); if (inner_field->flags & VMS_STRUCT) { ret = vmstate_save_state(f, inner_field->vmsd, diff --git a/scripts/analyze-migration.py b/scripts/analyze-migration.py index 134c25f20a..7f0797308d 100755 --- a/scripts/analyze-migration.py +++ b/scripts/analyze-migration.py @@ -501,15 +501,28 @@ def read(self): field['data'] = reader(field, self.file) field['data'].read() - if 'index' in field: - if field['name'] not in self.data: - self.data[field['name']] = [] - a = self.data[field['name']] - if len(a) != int(field['index']): - raise Exception("internal index of data field unmatched (%d/%d)" % (len(a), int(field['index']))) - a.append(field['data']) + fname = field['name'] + fdata = field['data'] + + # The field could be: + # i) a single data entry, e.g. uint64 + # ii) an array, indicated by it containing the 'index' key + # + # However, the overall data after parsing the whole + # stream, could be a mix of arrays and single data fields, + # all sharing the same field name due to how QEMU breaks + # up arrays with NULL pointers into multiple compressed + # array segments. + if fname not in self.data: + if 'index' in field: + self.data[fname] = [] + else: + self.data[fname] = fdata + elif type(self.data[fname]) == list: + self.data[fname].append(fdata) else: - self.data[field['name']] = field['data'] + tmp = self.data[fname] + self.data[fname] = [tmp, fdata] if 'subsections' in self.desc['struct']: for subsection in self.desc['struct']['subsections']: