From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <dev-bounces@dpdk.org>
Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124])
	by inbox.dpdk.org (Postfix) with ESMTP id E2BBBA054F;
	Mon,  1 Mar 2021 16:44:03 +0100 (CET)
Received: from [217.70.189.124] (localhost [127.0.0.1])
	by mails.dpdk.org (Postfix) with ESMTP id 7500422A2CE;
	Mon,  1 Mar 2021 16:44:03 +0100 (CET)
Received: from out0-152.mail.aliyun.com (out0-152.mail.aliyun.com
 [140.205.0.152]) by mails.dpdk.org (Postfix) with ESMTP id 9B13940041
 for <dev@dpdk.org>; Mon,  1 Mar 2021 16:44:01 +0100 (CET)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
 d=alibaba-inc.com; s=default;
 t=1614613438; h=Subject:To:From:Message-ID:Date:MIME-Version:Content-Type;
 bh=N03m1zZVmZVOum7upOAeLKz6DiiaFrS69OHvT/wJU20=;
 b=ZtPo0xERjg9iWC+NfKM2Vop8zs7k0UqZS4FaoPFgyv79q53Q5LskLOKuU/3NtS7bTcnoYQfRyRXiLnmgaRBjdwLSYFeupZHjSMPwHIQvJc/J+WgiYu0TwGc6R4TSdQ5aNeGMeI1dwNAvDeFy9uUSCTxSOVkF3OdhjtMiWeBg2Hc=
X-Alimail-AntiSpam: AC=PASS; BC=-1|-1; BR=01201311R191e4; CH=green; DM=||false|;
 DS=||; FP=0|-1|-1|-1|0|-1|-1|-1; HT=ay29a033018047188;
 MF=huawei.xhw@alibaba-inc.com; NM=1; PH=DS; RN=8; SR=0;
 TI=SMTPD_---.JeyCER0_1614613436; 
Received: from 30.15.219.167(mailfrom:huawei.xhw@alibaba-inc.com
 fp:SMTPD_---.JeyCER0_1614613436) by smtp.aliyun-inc.com(127.0.0.1);
 Mon, 01 Mar 2021 23:43:57 +0800
To: David Marchand <david.marchand@redhat.com>
Cc: Ferruh Yigit <ferruh.yigit@intel.com>,
 Maxime Coquelin <maxime.coquelin@redhat.com>, dev <dev@dpdk.org>,
 "Burakov, Anatoly" <anatoly.burakov@intel.com>, xuemingl@nvidia.com,
 Gaetan Rivet <grive@u256.net>, "Xia, Chenbo" <chenbo.xia@intel.com>
References: <1611890309-99135-1-git-send-email-huawei.xhw@alibaba-inc.com>
 <1614014118-91150-1-git-send-email-huawei.xhw@alibaba-inc.com>
 <1614014118-91150-3-git-send-email-huawei.xhw@alibaba-inc.com>
 <b34311c7-5b09-a1f6-1957-c9e19bb2a273@intel.com>
 <e53cfa75-4505-c0fe-2214-1d066b2e28ba@alibaba-inc.com>
 <08e5172f-36ce-13d9-5c96-9d6d1e71153a@intel.com>
 <967cfffb-1955-afc2-8479-0afa255b317f@alibaba-inc.com>
 <CAJFAV8w4qvrazksjvy4=5YUtQwRku_FQDMhhmv59-i8o8Zh-Fg@mail.gmail.com>
From: "=?UTF-8?B?6LCi5Y2O5LyfKOatpOaXtuatpOWIu++8iQ==?="
 <huawei.xhw@alibaba-inc.com>
Message-ID: <85a43efe-ef66-54c0-81b4-6e130a987699@alibaba-inc.com>
Date: Mon, 01 Mar 2021 23:43:50 +0800
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101
 Thunderbird/78.7.1
MIME-Version: 1.0
In-Reply-To: <CAJFAV8w4qvrazksjvy4=5YUtQwRku_FQDMhhmv59-i8o8Zh-Fg@mail.gmail.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit
Content-Language: en-US
Subject: Re: [dpdk-dev] [PATCH v7 2/2] bus/pci: support MMIO in PCI ioport
 accessors
X-BeenThere: dev@dpdk.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: DPDK patches and discussions <dev.dpdk.org>
List-Unsubscribe: <https://mails.dpdk.org/options/dev>,
 <mailto:dev-request@dpdk.org?subject=unsubscribe>
List-Archive: <http://mails.dpdk.org/archives/dev/>
List-Post: <mailto:dev@dpdk.org>
List-Help: <mailto:dev-request@dpdk.org?subject=help>
List-Subscribe: <https://mails.dpdk.org/listinfo/dev>,
 <mailto:dev-request@dpdk.org?subject=subscribe>
Errors-To: dev-bounces@dpdk.org
Sender: "dev" <dev-bounces@dpdk.org>


On 2021/2/25 17:52, David Marchand wrote:
> On Thu, Feb 25, 2021 at 5:00 AM 谢华伟(此时此刻) <huawei.xhw@alibaba-inc.com> wrote:
>>>>> Is the 'outb_p' to 'outb' conversion intentional? And if so why?
>>>>>
>>>>> Same of the all 'outb_p', 'outw_p', 'outl_p'.
>>>> There is no need to delay for virtio device, as we can see in virtio
>>>> legacy driver.
>>>>
>>>> IMO, the delay is for ugly old device. The device itself should
>>>> assure the previous IO completes when the subsequent IO instruction
>>>> arrives.
>>>>
>>> Can there be any virtio legacy device needing this?
>> The pause version delays sometime by writing to 0x80 debug port. virtio
>> doesn't need this. virtio legacy PMD driver doens't use this.
>>
>> Any device relying on this i think is buggy. How could the device rely
>> on some uncertain cpu cycles to behave correct?
>>
>>> What is the downside of using "pause until the I/O completes" versions?
>> The downside in virtio PMD is a small performance penalty when we use it
>> to notify backend. CPU executes unnecessary serializing IO instruction.
>>
>> I check kernel code, io wrapper for in/out doesn't use p version.
> This change is a fix/optimisation.
> This is a separate topic from adding MMIO support with x86 ioport.
> I would split as a separate patch.

Hi David:

Maybe there is confuse? There is no change. The out/in is added. I don't 
remove _p on purpose.

>
>