From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34323) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ehKv4-0004PC-7d for qemu-devel@nongnu.org; Thu, 01 Feb 2018 14:56:58 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ehKu0-00058q-80 for qemu-devel@nongnu.org; Thu, 01 Feb 2018 14:53:14 -0500 Received: from mx1.redhat.com ([209.132.183.28]:58426) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ehKtz-00058J-SB for qemu-devel@nongnu.org; Thu, 01 Feb 2018 14:52:08 -0500 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id F35BB72FEF for ; Thu, 1 Feb 2018 19:52:06 +0000 (UTC) Date: Thu, 1 Feb 2018 19:51:31 +0000 From: "Dr. David Alan Gilbert" Message-ID: <20180201195131.GO2457@work-vm> References: <20180201112028.23552-1-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180201112028.23552-1-peterx@redhat.com> Subject: Re: [Qemu-devel] [PATCH] pcie-root-port: let it has higher migrate priority List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Xu Cc: qemu-devel@nongnu.org, Alex Williamson , Marcel Apfelbaum , "Michael S . Tsirkin" , Juan Quintela , Laurent Vivier * Peter Xu (peterx@redhat.com) wrote: > In the past, we prioritized IOMMU migration so that we have such a > priority order: > > IOMMU > PCI Devices > > When migrating a guest with both vIOMMU and pcie-root-port, we'll always > migrate vIOMMU first, since pcie-root-port will be seen to have the same > priority of general PCI devices. > > That's problematic. > > The thing is that PCI bus number information is stored in the root port, > and that is needed by vIOMMU during post_load(), e.g., to figure out > context entry for a device. If we don't have correct bus numbers for > devices, we won't be able to recover device state of the DMAR memory > regions, and things will be messed up. > > So let's boost the PCIe root ports to be even with higher priority: > > PCIe Root Port > IOMMU > PCI Devices > > A smoke test shows that this patch fixes bug 1538953. Two questions (partially overlapping with what I replied to Michaels): a) What happens with multiple IOMMUs? b) What happens with multiple root ports? c) How correct is this ordering on different implementations (e.g. ARM/Power/etc) Dave > > CC: Alex Williamson > CC: Marcel Apfelbaum > CC: Michael S. Tsirkin > CC: Dr. David Alan Gilbert > CC: Juan Quintela > CC: Laurent Vivier > Bug: https://bugzilla.redhat.com/show_bug.cgi?id=1538953 > Reported-by: Maxime Coquelin > Signed-off-by: Peter Xu > --- > Marcel & all, > > I think it's possible that we need similar thing for other bridge-like > devices, but I'm not that familiar. Would you help confirm? Thanks, > --- > hw/pci-bridge/gen_pcie_root_port.c | 1 + > include/migration/vmstate.h | 1 + > 2 files changed, 2 insertions(+) > > diff --git a/hw/pci-bridge/gen_pcie_root_port.c b/hw/pci-bridge/gen_pcie_root_port.c > index 0e2f2e8bf1..e6ff1effd8 100644 > --- a/hw/pci-bridge/gen_pcie_root_port.c > +++ b/hw/pci-bridge/gen_pcie_root_port.c > @@ -101,6 +101,7 @@ static void gen_rp_realize(DeviceState *dev, Error **errp) > > static const VMStateDescription vmstate_rp_dev = { > .name = "pcie-root-port", > + .priority = MIG_PRI_PCIE_ROOT_PORT, > .version_id = 1, > .minimum_version_id = 1, > .post_load = pcie_cap_slot_post_load, > diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h > index 8c3889433c..491449db9f 100644 > --- a/include/migration/vmstate.h > +++ b/include/migration/vmstate.h > @@ -148,6 +148,7 @@ enum VMStateFlags { > typedef enum { > MIG_PRI_DEFAULT = 0, > MIG_PRI_IOMMU, /* Must happen before PCI devices */ > + MIG_PRI_PCIE_ROOT_PORT, /* Must happen before IOMMU */ > MIG_PRI_GICV3_ITS, /* Must happen before PCI devices */ > MIG_PRI_GICV3, /* Must happen before the ITS */ > MIG_PRI_MAX, > -- > 2.14.3 > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK