From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52225) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eh1tj-0002uL-9u for qemu-devel@nongnu.org; Wed, 31 Jan 2018 18:34:36 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eh1tf-0005KN-Cb for qemu-devel@nongnu.org; Wed, 31 Jan 2018 18:34:35 -0500 Received: from mx1.redhat.com ([209.132.183.28]:58548) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eh1tf-0005Ip-5Y for qemu-devel@nongnu.org; Wed, 31 Jan 2018 18:34:31 -0500 Date: Wed, 31 Jan 2018 21:34:22 -0200 From: Eduardo Habkost Message-ID: <20180131233422.GP26425@localhost.localdomain> References: <20180117095421.124787-1-marcel@redhat.com> <20180117095421.124787-2-marcel@redhat.com> <20180131204059.GG21702@localhost.localdomain> <20180131230607-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180131230607-mutt-send-email-mst@kernel.org> Subject: Re: [Qemu-devel] [PATCH V8 1/4] mem: add share parameter to memory-backend-ram List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: Marcel Apfelbaum , qemu-devel@nongnu.org, cohuck@redhat.com, f4bug@amsat.org, yuval.shaia@oracle.com, borntraeger@de.ibm.com, pbonzini@redhat.com, imammedo@redhat.com On Wed, Jan 31, 2018 at 11:10:07PM +0200, Michael S. Tsirkin wrote: > On Wed, Jan 31, 2018 at 06:40:59PM -0200, Eduardo Habkost wrote: > > On Wed, Jan 17, 2018 at 11:54:18AM +0200, Marcel Apfelbaum wrote: > > > Currently only file backed memory backend can > > > be created with a "share" flag in order to allow > > > sharing guest RAM with other processes in the host. > > > > > > Add the "share" flag also to RAM Memory Backend > > > in order to allow remapping parts of the guest RAM > > > to different host virtual addresses. This is needed > > > by the RDMA devices in order to remap non-contiguous > > > QEMU virtual addresses to a contiguous virtual address range. > > > > > > > Why do we need to make this configurable? Would anything break > > if MAP_SHARED was always used if possible? > > See Documentation/vm/numa_memory_policy.txt for a list > of complications. Ew. > > Maybe we should more of an effort to detect and report these > issues. Probably. Having other features breaking silently when using pvrdma doesn't sound good. We must at least document those problems in the documentation for memory-backend-ram. BTW, what's the root cause for requiring HVAs in the buffer? Can this be fixed? -- Eduardo