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[88.21.201.17]) by smtp.gmail.com with ESMTPSA id 64sm7194615wmz.7.2021.04.01.01.26.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 01 Apr 2021 01:26:30 -0700 (PDT) Subject: Re: [PATCH v3 02/11] esp: rework write_response() to avoid using the FIFO for DMA transactions To: Mark Cave-Ayland , qemu-devel@nongnu.org, alxndr@bu.edu, laurent@vivier.eu, pbonzini@redhat.com References: <20210401074933.9923-1-mark.cave-ayland@ilande.co.uk> <20210401074933.9923-3-mark.cave-ayland@ilande.co.uk> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: Date: Thu, 1 Apr 2021 10:26:29 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: <20210401074933.9923-3-mark.cave-ayland@ilande.co.uk> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::42e; envelope-from=philippe.mathieu.daude@gmail.com; helo=mail-wr1-x42e.google.com X-Spam_score_int: -14 X-Spam_score: -1.5 X-Spam_bar: - X-Spam_report: (-1.5 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FORGED_FROMDOMAIN=0.249, FREEMAIL_FROM=0.001, HEADER_FROM_DIFFERENT_DOMAINS=0.249, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 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" On 4/1/21 9:49 AM, Mark Cave-Ayland wrote: > The code for write_response() has always used the FIFO to store the data for > the status/message in phases, even for DMA transactions. Switch to using a > separate buffer that can be used directly for DMA transactions and restrict > the FIFO use to the non-DMA case. > > Signed-off-by: Mark Cave-Ayland > --- > hw/scsi/esp.c | 13 ++++++------- > 1 file changed, 6 insertions(+), 7 deletions(-) > > diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c > index bafea0d4e6..26fe1dcb9d 100644 > --- a/hw/scsi/esp.c > +++ b/hw/scsi/esp.c > @@ -445,18 +445,16 @@ static void write_response_pdma_cb(ESPState *s) > > static void write_response(ESPState *s) > { > - uint32_t n; > + uint8_t buf[2]; > > trace_esp_write_response(s->status); > > - fifo8_reset(&s->fifo); > - esp_fifo_push(s, s->status); > - esp_fifo_push(s, 0); > + buf[0] = s->status; > + buf[1] = 0; Slightly simplified: const uint8_t buf[2] = { s->status, 0 }; > if (s->dma) { uint32_t n; > if (s->dma_memory_write) { > - s->dma_memory_write(s->dma_opaque, > - (uint8_t *)fifo8_pop_buf(&s->fifo, 2, &n), 2); > + s->dma_memory_write(s->dma_opaque, buf, 2); > s->rregs[ESP_RSTAT] = STAT_TC | STAT_ST; > s->rregs[ESP_RINTR] |= INTR_BS | INTR_FC; > s->rregs[ESP_RSEQ] = SEQ_CD; > @@ -466,7 +464,8 @@ static void write_response(ESPState *s) > return; > } > } else { > - s->ti_size = 2; > + fifo8_reset(&s->fifo); > + fifo8_push_all(&s->fifo, buf, 2); > s->rregs[ESP_RFLAGS] = 2; > } > esp_raise_irq(s); > Reviewed-by: Philippe Mathieu-Daudé