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 67EE0C83F1D for ; Tue, 15 Jul 2025 06:28:05 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ubZ3Y-0005al-3c; Tue, 15 Jul 2025 02:22:24 -0400 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 1ubZ1w-0003UX-OR for qemu-devel@nongnu.org; Tue, 15 Jul 2025 02:21:01 -0400 Received: from mail-wr1-x435.google.com ([2a00:1450:4864:20::435]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1ubZ1r-0007RW-CJ for qemu-devel@nongnu.org; Tue, 15 Jul 2025 02:20:41 -0400 Received: by mail-wr1-x435.google.com with SMTP id ffacd0b85a97d-3a4e742dc97so3551770f8f.0 for ; Mon, 14 Jul 2025 23:20:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1752560435; x=1753165235; darn=nongnu.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=AAAEB3eVJKoeoejF7sQrJUuJBjbwnpIt5RH1cN5JYiQ=; b=aRo+vdHm6y4mNOdyIpRrV/b5qAJtOH4n/l8/LKrIUJzxBVcZJdwP+hBQzmxxZHvzt+ pbGTwhvBRhscR07QfbSQSeTwcp7FuIlx701TkUNLa/jnFwiz1qm15bdl7Z6sAbwTy8gQ Jf0kRnZz1Mz05mUrAgzIKysGonDHhsCeQUKwYAtCdc6TdIys69YyjdTZe460IOXiW5+W 6gMAs7ykCIYrF1VYjB1vUSoP8WlB821brqArKqO0Frx+ZVLO4TYC6GwE9J1GMxbAQCUw 9PSsHLiEr5U6XBqurg17MKJOOOW5aynkvX0h99Mw1kCpBeoMxb6yDOSQmLIutRrObPf6 pM/w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1752560435; x=1753165235; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=AAAEB3eVJKoeoejF7sQrJUuJBjbwnpIt5RH1cN5JYiQ=; b=Gso4BCTUut37I+YQQ8S3UdiIiKhdwq5Xts89iQFq23h8ibkef8Rt98KLsu9B03vrh9 iTD+v4Ncfi+2uSxpvI+q6T8WK2LiUsdS0OSpUeeBxcoSa1stpZVAF+CuQicfQyPv61kV WbNIUJC7/ZdHYUORLzezdAQRig90WBxvQLzEALEXraKtoXffTuub/lu+iG4Hu8JS2zXj lvV+lLeDSk0GvwHLYs62BW0BbumuouQqvlqAs1JO+XBRIzg/Z/Mtlm7/w9h3ea+Jjllv 0Nuz/zMgbZmjgJMzdsDn8w6m3YHpuSyiI2308kqWSuiy0IU6I61MVCAAg5c3d/zpRCxP Oj7A== X-Gm-Message-State: AOJu0YxbW5/REr73YNgzbZQL3d0UCi0CZAAq63HM++KaEiBH43+yk/5n Z7oP31uppWT4hMmSgD6znz4oTk1cEyLUXU7YbcRQSGTxDiZQpip61Gnr2n4mXpTkJZ/IkqLAbv4 wqwkn X-Gm-Gg: ASbGncsZio1POsifwxZdQ0cLn0sHZNVf9Nbd9rs3D/DPQBjq4etkNYWYjy/H3a/CdSE Xf1dIVsVr2mPomapj6id8mP3qXTidDHbNMkUJTRDgeeZJLgFg5twOLyTgyCmdwnaq5A+dIrq4rW FH7gd/9vAGuU9YVHWxTDu7z1vdSa2jOsdHZ/Y84g9PImpeHj/B2Wx6bZdkca1P++B4xBhTVsP0F awhYpc3I5+fTLpy893a0uHADXJZ7618uz+D22E956VdrQW9ed7fi2n53k7kZoAtCxHFyRLeN8St 2B8UATVSQSXpdUaW023kK4iQIG/0RWUlizOTACCKyj76qK0BqncAr0n+Zz1DxxlyXwKnf/lL1CU ruNNI1E/PoA12XSXR//OazIV3RG/0TLduyXDmVF7ZI1MX4f71X1QDlrL1IWy9FZ0w0Sl0gAc0FR nliXa7M8M= X-Google-Smtp-Source: AGHT+IE4kM2zPLwHhA8KcuIIH8p3I9fuc0n6FZDfc1V21iDYd5ErMap3SVHNE2uZlFs7uRpHnPFVzQ== X-Received: by 2002:a05:6000:2307:b0:3a5:8934:4959 with SMTP id ffacd0b85a97d-3b609544322mr1440705f8f.27.1752560435072; Mon, 14 Jul 2025 23:20:35 -0700 (PDT) Received: from localhost.localdomain (88-187-86-199.subs.proxad.net. [88.187.86.199]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-454d5032e9esm190623215e9.3.2025.07.14.23.20.34 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Mon, 14 Jul 2025 23:20:34 -0700 (PDT) From: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= To: qemu-devel@nongnu.org Cc: Mark Cave-Ayland , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , Paolo Bonzini , Fam Zheng Subject: [PULL 15/17] esp.c: only call dma_memory_write function if transfer length is non-zero Date: Tue, 15 Jul 2025 08:19:15 +0200 Message-ID: <20250715061918.44971-16-philmd@linaro.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250715061918.44971-1-philmd@linaro.org> References: <20250715061918.44971-1-philmd@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::435; envelope-from=philmd@linaro.org; helo=mail-wr1-x435.google.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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, 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: Mark Cave-Ayland In the cases where mixed DMA/non-DMA transfers are used or no data is available, it is possible for the calculated transfer length to be zero. Only call the dma_memory_write function where the transfer length is non-zero to avoid invoking the DMA engine for a zero length transfer which can have side-effects (along with generating additional tracing noise). Signed-off-by: Mark Cave-Ayland Reviewed-by: Philippe Mathieu-Daudé Tested-by: Philippe Mathieu-Daudé Message-ID: <20250711204636.542964-6-mark.cave-ayland@ilande.co.uk> Signed-off-by: Philippe Mathieu-Daudé --- hw/scsi/esp.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c index ec9fcbeddf4..1c7bad8fc02 100644 --- a/hw/scsi/esp.c +++ b/hw/scsi/esp.c @@ -631,7 +631,9 @@ static void esp_do_dma(ESPState *s) switch (s->rregs[ESP_CMD]) { case CMD_TI | CMD_DMA: if (s->dma_memory_write) { - s->dma_memory_write(s->dma_opaque, s->async_buf, len); + if (len) { + s->dma_memory_write(s->dma_opaque, s->async_buf, len); + } } else { /* Copy device data to FIFO */ len = MIN(len, fifo8_num_free(&s->fifo)); @@ -681,6 +683,7 @@ static void esp_do_dma(ESPState *s) buf[0] = s->status; if (s->dma_memory_write) { + /* Length already non-zero */ s->dma_memory_write(s->dma_opaque, buf, len); } else { esp_fifo_push_buf(s, buf, len); @@ -715,6 +718,7 @@ static void esp_do_dma(ESPState *s) buf[0] = 0; if (s->dma_memory_write) { + /* Length already non-zero */ s->dma_memory_write(s->dma_opaque, buf, len); } else { esp_fifo_push_buf(s, buf, len); -- 2.49.0