From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56682) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YIZI1-0001zy-UZ for qemu-devel@nongnu.org; Tue, 03 Feb 2015 03:56:58 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YIZHw-0007iV-3b for qemu-devel@nongnu.org; Tue, 03 Feb 2015 03:56:57 -0500 Received: from e28smtp05.in.ibm.com ([122.248.162.5]:42222) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YIZHv-0007hU-Ff for qemu-devel@nongnu.org; Tue, 03 Feb 2015 03:56:52 -0500 Received: from /spool/local by e28smtp05.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 3 Feb 2015 14:26:47 +0530 From: Nikunj A Dadhania In-Reply-To: <1422943851-25836-1-git-send-email-david@gibson.dropbear.id.au> References: <1422943851-25836-1-git-send-email-david@gibson.dropbear.id.au> Date: Tue, 03 Feb 2015 14:26:44 +0530 Message-ID: <87pp9rweyb.fsf@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [Qemu-ppc] [RFC] pseries: Enable in-kernel H_LOGICAL_CI_{LOAD, STORE} implementations List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Gibson , aik@ozlabs.ru, agraf@suse.de, mdroth@us.ibm.com Cc: paulus@samba.org, qemu-ppc@nongnu.org, qemu-devel@nongnu.org David Gibson writes: > qemu currently implements the hypercalls H_LOGICAL_CI_LOAD and > H_LOGICAL_CI_STORE as PAPR extensions. These are used by the SLOF firmware > for IO, because performing cache inhibited MMIO accesses with the MMU off > (real mode) is very awkward on POWER. > > This approach breaks when SLOF needs to access IO devices implemented > within KVM instead of in qemu. The simplest example would be virtio-blk > using an iothread, because the iothread / dataplane mechanism relies on > an in-kernel implementation of the virtio queue notification MMIO. > > To fix this, an in-kernel implementation of these hypercalls has been made, > however, the hypercalls still need to be enabled from qemu. This performs > the necessary calls to do so. > > Signed-off-by: David Gibson Reviewed-by: Nikunj A Dadhania