From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pankaj Gupta Subject: Re: [Qemu-devel] [RFC 2/2] KVM: add virtio-pmem driver Date: Tue, 17 Oct 2017 03:40:56 -0400 (EDT) Message-ID: <1441791227.21027037.1508226056893.JavaMail.zimbra@redhat.com> References: <20171012155027.3277-1-pagupta@redhat.com> <20171012155027.3277-3-pagupta@redhat.com> <20171017071633.GA9207@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20171017071633.GA9207@infradead.org> Sender: linux-kernel-owner@vger.kernel.org To: Christoph Hellwig Cc: kwolf@redhat.com, haozhong zhang , jack@suse.cz, xiaoguangrong eric , kvm@vger.kernel.org, david@redhat.com, linux-nvdimm@ml01.01.org, ross zwisler , linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, linux-mm@kvack.org, stefanha@redhat.com, pbonzini@redhat.com, dan j williams , nilal@redhat.com List-Id: linux-nvdimm@lists.01.org > > I think this driver is at entirely the wrong level. > > If you want to expose pmem to a guest with flushing assist do it > as pmem, and not a block driver. Are you saying do it as existing i.e ACPI pmem like interface? The reason we have created this new driver is exiting pmem driver does not define proper semantics for guest flushing requests. Regarding block support of driver, we want to achieve DAX support to bypass guest page cache. Also, we want to utilize existing DAX capable file-system interfaces(e.g fsync) from userspace file API's to trigger the host side flush request. Below link has details of previous discussion: https://marc.info/?l=kvm&m=150091133700361&w=2 Thanks, Pankaj From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f197.google.com (mail-qk0-f197.google.com [209.85.220.197]) by kanga.kvack.org (Postfix) with ESMTP id E0F856B0038 for ; Tue, 17 Oct 2017 03:41:05 -0400 (EDT) Received: by mail-qk0-f197.google.com with SMTP id q83so1049733qke.16 for ; Tue, 17 Oct 2017 00:41:05 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id s5si66247qkb.412.2017.10.17.00.41.05 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 17 Oct 2017 00:41:05 -0700 (PDT) Date: Tue, 17 Oct 2017 03:40:56 -0400 (EDT) From: Pankaj Gupta Message-ID: <1441791227.21027037.1508226056893.JavaMail.zimbra@redhat.com> In-Reply-To: <20171017071633.GA9207@infradead.org> References: <20171012155027.3277-1-pagupta@redhat.com> <20171012155027.3277-3-pagupta@redhat.com> <20171017071633.GA9207@infradead.org> Subject: Re: [Qemu-devel] [RFC 2/2] KVM: add virtio-pmem driver MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Hellwig Cc: kwolf@redhat.com, haozhong zhang , jack@suse.cz, xiaoguangrong eric , kvm@vger.kernel.org, david@redhat.com, linux-nvdimm@ml01.01.org, ross zwisler , linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, linux-mm@kvack.org, stefanha@redhat.com, pbonzini@redhat.com, dan j williams , nilal@redhat.com > > I think this driver is at entirely the wrong level. > > If you want to expose pmem to a guest with flushing assist do it > as pmem, and not a block driver. Are you saying do it as existing i.e ACPI pmem like interface? The reason we have created this new driver is exiting pmem driver does not define proper semantics for guest flushing requests. Regarding block support of driver, we want to achieve DAX support to bypass guest page cache. Also, we want to utilize existing DAX capable file-system interfaces(e.g fsync) from userspace file API's to trigger the host side flush request. Below link has details of previous discussion: https://marc.info/?l=kvm&m=150091133700361&w=2 Thanks, Pankaj -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org