From owner-freebsd-scsi@FreeBSD.ORG Fri Nov 7 14:23:24 2014 Return-Path: Delivered-To: freebsd-scsi@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 92BF6E1D for ; Fri, 7 Nov 2014 14:23:24 +0000 (UTC) Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 1F308B3A for ; Fri, 7 Nov 2014 14:23:23 +0000 (UTC) Received: from tom.home (kostik@localhost [127.0.0.1]) by kib.kiev.ua (8.14.9/8.14.9) with ESMTP id sA7ENAvv058606 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Fri, 7 Nov 2014 16:23:10 +0200 (EET) (envelope-from kostikbel@gmail.com) DKIM-Filter: OpenDKIM Filter v2.9.2 kib.kiev.ua sA7ENAvv058606 Received: (from kostik@localhost) by tom.home (8.14.9/8.14.9/Submit) id sA7EN9PY058605; Fri, 7 Nov 2014 16:23:09 +0200 (EET) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com using -f Date: Fri, 7 Nov 2014 16:23:09 +0200 From: Konstantin Belousov To: Sibananda Sahu Subject: Re: Query regarding Unmapped IO, PIM_UNMAPPED and bus_dmamap_load_ccb() Message-ID: <20141107142309.GR53947@kib.kiev.ua> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-Spam-Status: No, score=-2.0 required=5.0 tests=ALL_TRUSTED,BAYES_00, DKIM_ADSP_CUSTOM_MED,FREEMAIL_FROM,NML_ADSP_CUSTOM_MED autolearn=no autolearn_force=no version=3.4.0 X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on tom.home Cc: freebsd-scsi@freebsd.org X-BeenThere: freebsd-scsi@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: SCSI subsystem List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 07 Nov 2014 14:23:24 -0000 On Fri, Nov 07, 2014 at 05:07:59AM +0530, Sibananda Sahu wrote: > Hi All, > > > > I have raised this query regarding the following mail: > > https://lists.freebsd.org/pipermail/freebsd-scsi/2014-July/006407.html > > > > Where Alexander Motin talks of Unmapped I/O. > > As per his direction I have declared the below statement in my driver code: > > > > ccb->cpi.hba_misc = PIM_NOBUSRESET | PIM_UNMAPPED; > > > > Before enabling PIM_UNMAPPED I was getting the (ccb->ccb_h.flags & > CAM_DATA_MASK) as CAM_DATA_VADDR and handling accordingly. > > But after enabling PIM_UNMAPPED in cpi.hba_misc I am getting the > (ccb->ccb_h.flags & CAM_DATA_MASK) as CAM_DATA_BIO and handling the data > that comes with bus_dma_load_ccb(). Right. Look at the code. In particular, the definition of the struct bio in sys/sys/bio.h. There, the buffer pointed by bio_data is passed if BIO_UNMAPPED flag is not set, but when the flag is set, bio_ma* fields describe an array of physical memory pages where the data for i/o request are scattered. The pages are not neccessary mapped into the KVA, which explains the terminology. The i/o stack and busdma(9) where modified to transparently handle such requests, and you correctly described the minimal changes, required from the driver side to process the unmapped requests. The passing of a pointer to bio instead of the pointer to buffer allows drivers to not care about mapped/not mapped requests, assuming the suitable KPI like bus_dma_load_ccb() prepares the buffer for dma engine of the controller. > > > > I just did the same thing according to the mps(4) driver as referred by > Alexander Motin. > > > > So I just wanted to know what exactly happening when I am enabling the > PIM_UNMAPPED in the cpi.hba_misc field. > > And what the CAM_DATA_BIO really means in the CAM_DATA_MASK. > > > > > > It would be great idea if somebody explains what exactly happening or at > least give me some references where can I have a look and move forward. > > > > > > Thanks, > > Sibananda Sahu > _______________________________________________ > freebsd-scsi@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-scsi > To unsubscribe, send any mail to "freebsd-scsi-unsubscribe@freebsd.org"