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Tue, 13 Oct 2020 09:37:48 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 84596f92-858b-4962-86d2-6a2f0808ccdb; Tue, 13 Oct 2020 09:37:47 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 66112B00A; Tue, 13 Oct 2020 09:37:46 +0000 (UTC) Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kSGke-0005rB-KC for xen-devel@lists.xen.org; Tue, 13 Oct 2020 09:37:48 +0000 X-Inumbo-ID: 84596f92-858b-4962-86d2-6a2f0808ccdb Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 84596f92-858b-4962-86d2-6a2f0808ccdb; Tue, 13 Oct 2020 09:37:47 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1602581866; 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=FWFovjq8UywOZdRtko2zvRMKBxqypmNrhXV85DC7h+U=; b=jH8U92HEQqgXJ5pB6jF5FXIZiQtJn486VutZMkuKigLD6MpEO/bgaKZ747vRgMaIw/86hF 3M5TkcwvTB8VFWszKq6oJJkz4xmuT152iNpqA+cwuDUlxt2IPMdVH27s6xTq3UaxvDs9EP F728AJ9R6Z/+t5Kaku+Wj7iimWN3Poo= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 66112B00A; Tue, 13 Oct 2020 09:37:46 +0000 (UTC) Subject: Re: [XEN PATCH v14 7/8] Add IOREQ_TYPE_VMWARE_PORT To: paul@xen.org Cc: 'Don Slutz' , xen-devel@lists.xen.org, 'Boris Ostrovsky' , 'Ian Jackson' , 'Jun Nakajima' , 'Kevin Tian' , 'Stefano Stabellini' , 'Tim Deegan' , 'Andrew Cooper' , 'Konrad Rzeszutek Wilk' , 'George Dunlap' References: <000901d69bb8$941489b0$bc3d9d10$@xen.org> From: Jan Beulich Message-ID: <8bf54ee4-2379-f3eb-57a4-ee572978d219@suse.com> Date: Tue, 13 Oct 2020 11:37:44 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <000901d69bb8$941489b0$bc3d9d10$@xen.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 06.10.2020 10:13, Paul Durrant wrote: > > >> -----Original Message----- >> From: Jan Beulich >> Sent: 01 October 2020 15:42 >> To: Don Slutz >> Cc: xen-devel@lists.xen.org; Boris Ostrovsky ; Ian Jackson >> ; Jun Nakajima ; Kevin Tian ; >> Stefano Stabellini ; Tim Deegan ; Andrew Cooper >> ; Konrad Rzeszutek Wilk ; George Dunlap >> ; Paul Durrant >> Subject: Re: [XEN PATCH v14 7/8] Add IOREQ_TYPE_VMWARE_PORT >> >> On 19.08.2020 18:52, Don Slutz wrote: >>> This adds synchronization of the 6 vcpu registers (only 32bits of >>> them) that QEMU's vmport.c and vmmouse.c needs between Xen and QEMU. >>> This is how VMware defined the use of these registers. >>> >>> This is to avoid a 2nd and 3rd exchange between QEMU and Xen to >>> fetch and put these 6 vcpu registers used by the code in QEMU's >>> vmport.c and vmmouse.c >> >> I'm unconvinced this warrants a new ioreq type, and all the overhead >> associated with it. I'd be curious to know what Paul or the qemu >> folks think here. >> > > The current shared ioreq_t does appear have enough space to accommodate 6 32-bit registers (in the addr, data, count and size) fields co couldn't the new IOREQ_TYPE_VMWARE_PORT type be dealt with by simply unioning the regs with these fields? That avoids the need for a whole new shared page. Hmm, yes, good point. But this is assuming we're going to be fine with using 32-bit registers now and going forward. Personally I'd prefer a mechanism less constrained by the specific needs of the current VMware interface, i.e. potentially allowing to scale to 64-bit registers as well as any of the remaining 9 ones (leaving aside %rsp). Jan