From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46793) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eYq2l-00057E-8q for qemu-devel@nongnu.org; Tue, 09 Jan 2018 04:18:04 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eYq2h-0007c4-80 for qemu-devel@nongnu.org; Tue, 09 Jan 2018 04:18:03 -0500 Received: from mx1.redhat.com ([209.132.183.28]:55146) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eYq2h-0007bi-1O for qemu-devel@nongnu.org; Tue, 09 Jan 2018 04:17:59 -0500 Date: Tue, 9 Jan 2018 10:17:48 +0100 From: Cornelia Huck Message-ID: <20180109101748.4cfeda03.cohuck@redhat.com> In-Reply-To: <20180107123224.100877-4-marcel@redhat.com> References: <20180107123224.100877-1-marcel@redhat.com> <20180107123224.100877-4-marcel@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH V6 3/5] docs: add pvrdma device documentation. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Marcel Apfelbaum Cc: qemu-devel@nongnu.org, ehabkost@redhat.com, imammedo@redhat.com, yuval.shaia@oracle.com, pbonzini@redhat.com, mst@redhat.com, borntraeger@de.ibm.com On Sun, 7 Jan 2018 14:32:22 +0200 Marcel Apfelbaum wrote: > Signed-off-by: Marcel Apfelbaum > Signed-off-by: Yuval Shaia > Reviewed-by: Shamir Rabinovitch > --- > docs/pvrdma.txt | 254 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 254 insertions(+) > create mode 100644 docs/pvrdma.txt > +5. Limitations > +============== > +- The device obviously is limited by the Guest Linux Driver features implementation > + of the VMware device API. > +- Memory registration mechanism requires mremap for every page in the buffer in order > + to map it to a contiguous virtual address range. Since this is not the data path > + it should not matter much. > +- The device requires target page size to be the same as the host page size. > +- QEMU cannot map guest RAM from a file descriptor if a pvrdma device is attached, > + so it can't work with huge pages. The limitation will be addressed in the future, > + however QEMU allocates Gust RAM with MADV_HUGEPAGE so if there are enough huge s/Gust/Guest/ > + pages available, QEMU will use them. > +- As previously stated, migration is not supported yet, however with some hardware > + support can be done.