From mboxrd@z Thu Jan 1 00:00:00 1970 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 641DCC25B4E for ; Fri, 20 Jan 2023 12:31:15 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pIqTt-0002aM-SQ; Fri, 20 Jan 2023 07:26:53 -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 1pIqTo-0002R0-EM for qemu-devel@nongnu.org; Fri, 20 Jan 2023 07:26:49 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pIqTl-0000Gy-MH for qemu-devel@nongnu.org; Fri, 20 Jan 2023 07:26:48 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1674217602; 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=j3CH6oLgoMZSvXdwH2OLunxeLunxPN5YJK8EBPDGf8E=; b=bQrAp9I2s9wpwiwKdiRqnpEifORabKR8QKkBZmh/ESQsW2uyiUFD5tX85V2hOQWTZVPSeB n1G7hgRp3m7CmdIYscm6dQFVu/rYbBv/RAz7CyYGStbicwe6f2CO/WI5e8n+RU3AA8nmff frbUNn37S9L+9mSC1BYuFeR5R98o91I= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-650-7xhM8ixoN4O3WBUW4sEdjA-1; Fri, 20 Jan 2023 07:26:41 -0500 X-MC-Unique: 7xhM8ixoN4O3WBUW4sEdjA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 2EB042801E50; Fri, 20 Jan 2023 12:26:41 +0000 (UTC) Received: from merkur.fritz.box (unknown [10.39.193.74]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6369240C6EC4; Fri, 20 Jan 2023 12:26:40 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, peter.maydell@linaro.org, qemu-devel@nongnu.org Subject: [PULL 03/38] pflash: Only read non-zero parts of backend image Date: Fri, 20 Jan 2023 13:25:58 +0100 Message-Id: <20230120122633.84983-4-kwolf@redhat.com> In-Reply-To: <20230120122633.84983-1-kwolf@redhat.com> References: <20230120122633.84983-1-kwolf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_H2=-0.001, 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 From: Xiang Zheng Currently we fill the VIRT_FLASH memory space with two 64MB NOR images when using persistent UEFI variables on virt board. Actually we only use a very small(non-zero) part of the memory while the rest significant large(zero) part of memory is wasted. So this patch checks the block status and only writes the non-zero part into memory. This requires pflash devices to use sparse files for backends. Signed-off-by: Xiang Zheng [ kraxel: rebased to latest master ] Signed-off-by: Gerd Hoffmann Message-Id: <20221220084246.1984871-1-kraxel@redhat.com> Reviewed-by: Daniel P. Berrangé Reviewed-by: Kevin Wolf Signed-off-by: Kevin Wolf --- hw/block/block.c | 36 +++++++++++++++++++++++++++++++++++- 1 file changed, 35 insertions(+), 1 deletion(-) diff --git a/hw/block/block.c b/hw/block/block.c index f9c4fe6767..142ebe4267 100644 --- a/hw/block/block.c +++ b/hw/block/block.c @@ -14,6 +14,40 @@ #include "qapi/error.h" #include "qapi/qapi-types-block.h" +/* + * Read the non-zeroes parts of @blk into @buf + * Reading all of the @blk is expensive if the zeroes parts of @blk + * is large enough. Therefore check the block status and only write + * the non-zeroes block into @buf. + * + * Return 0 on success, non-zero on error. + */ +static int blk_pread_nonzeroes(BlockBackend *blk, hwaddr size, void *buf) +{ + int ret; + int64_t bytes, offset = 0; + BlockDriverState *bs = blk_bs(blk); + + for (;;) { + bytes = MIN(size - offset, BDRV_REQUEST_MAX_SECTORS); + if (bytes <= 0) { + return 0; + } + ret = bdrv_block_status(bs, offset, bytes, &bytes, NULL, NULL); + if (ret < 0) { + return ret; + } + if (!(ret & BDRV_BLOCK_ZERO)) { + ret = bdrv_pread(bs->file, offset, bytes, + (uint8_t *) buf + offset, 0); + if (ret < 0) { + return ret; + } + } + offset += bytes; + } +} + /* * Read the entire contents of @blk into @buf. * @blk's contents must be @size bytes, and @size must be at most @@ -53,7 +87,7 @@ bool blk_check_size_and_read_all(BlockBackend *blk, void *buf, hwaddr size, * block device and read only on demand. */ assert(size <= BDRV_REQUEST_MAX_BYTES); - ret = blk_pread(blk, 0, size, buf, 0); + ret = blk_pread_nonzeroes(blk, size, buf); if (ret < 0) { error_setg_errno(errp, -ret, "can't read block backend"); return false; -- 2.38.1