From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756876AbeDZQn2 (ORCPT ); Thu, 26 Apr 2018 12:43:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41016 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756855AbeDZQnZ (ORCPT ); Thu, 26 Apr 2018 12:43:25 -0400 Date: Thu, 26 Apr 2018 12:43:24 -0400 (EDT) From: Pankaj Gupta To: Stefan Hajnoczi Cc: jack@suse.cz, kvm@vger.kernel.org, david@redhat.com, linux-nvdimm@ml01.01.org, ross zwisler , qemu-devel@nongnu.org, lcapitulino@redhat.com, linux-mm@kvack.org, niteshnarayanlal@hotmail.com, mst@redhat.com, hch@infradead.org, marcel@redhat.com, nilal@redhat.com, haozhong zhang , riel@surriel.com, stefanha@redhat.com, pbonzini@redhat.com, dan j williams , kwolf@redhat.com, xiaoguangrong eric , linux-kernel@vger.kernel.org, imammedo@redhat.com Message-ID: <358601698.23011599.1524761004239.JavaMail.zimbra@redhat.com> In-Reply-To: <20180426132406.GC30991@stefanha-x1.localdomain> References: <20180425112415.12327-1-pagupta@redhat.com> <20180425112415.12327-4-pagupta@redhat.com> <20180426132406.GC30991@stefanha-x1.localdomain> Subject: Re: [Qemu-devel] [RFC v2] qemu: Add virtio pmem device MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.116.119, 10.4.195.10] Thread-Topic: qemu: Add virtio pmem device Thread-Index: PlRV3tv3ry9/+W0+2e0WmSRmQm7QNg== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > +static void virtio_pmem_flush(VirtIODevice *vdev, VirtQueue *vq) > > +{ > > + VirtQueueElement *elem; > > + VirtIOPMEM *pmem = VIRTIO_PMEM(vdev); > > + HostMemoryBackend *backend = MEMORY_BACKEND(pmem->memdev); > > + int fd = memory_region_get_fd(&backend->mr); > > + > > + elem = virtqueue_pop(vq, sizeof(VirtQueueElement)); > > + if (!elem) { > > + return; > > + } > > + /* flush raw backing image */ > > + fsync(fd); > > fsync(2) is a blocking syscall. This can hang QEMU for an unbounded > amount of time. o.k. Main thread will block, agree. > > Please do the fsync from a thread pool. See block/file-posix.c's > aio_worker() for an example. Sure! > > > +static void virtio_pmem_get_config(VirtIODevice *vdev, uint8_t *config) > > +{ > > + VirtIOPMEM *pmem = VIRTIO_PMEM(vdev); > > + struct virtio_pmem_config *pmemcfg = (struct virtio_pmem_config *) > > config; > > + > > + pmemcfg->start = pmem->start; > > + pmemcfg->size = pmem->size; > > Endianness. Please use virtio_st*_p() instead. sure. > > > +#define VIRTIO_PMEM_PLUG 0 > > What is this? will remove Thanks, Pankaj