From: Stefano Stabellini <stefano.stabellini@eu.citrix.com> To: Gerd Hoffmann <kraxel@redhat.com> Cc: igvt-g@ml01.01.org, xen-devel@lists.xensource.com, Eduardo Habkost <ehabkost@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>, Andrew Cooper <andrew.cooper3@citrix.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, qemu-devel@nongnu.org, Jan Beulich <JBeulich@novell.com>, Cao jin <caoj.fnst@cn.fujitsu.com>, vfio-users@redhat.com, Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <rth@twiddle.net> Subject: Re: [Qemu-devel] [PATCH v3 11/11] igd: move igd-passthrough-isa-bridge creation to machine init Date: Thu, 7 Jan 2016 13:10:44 +0000 [thread overview] Message-ID: <alpine.DEB.2.02.1601071200210.13564@kaball.uk.xensource.com> (raw) In-Reply-To: <1452152339.6096.78.camel@redhat.com> CC'ing the Xen x86 maintainers On Thu, 7 Jan 2016, Gerd Hoffmann wrote: > Hi, > > > One thing I don't like about this is that it is going to skip the checks > > done in xen_pt_initfn. > > Hmm? Those checks are still done when you assign a igd ... Their failure doesn't affect the creation of the bridge. > > For example it is going to create the isa bridge, > > even if there is going to be an error loading the vga bios or if the > > device specified is not even an Intel graphic card. > > Creating the special igd-isa-bridge is no longer tied to actually > assigning a igd, but to the igd-passthru=on machine option being present > (and machine type being 'pc'). and machine type 'xenfv', unless I am mistaken? > xen_pt_initfn checks that igd-passthru=on is set in case it finds a igd > device is assigned, that will make sure the igd-isa-bridge is present. > > But, yes, you can create a igd-isa-bridge now even when not assigning a > igd device, either by specifying igd-passthru=on or using -device. I > fail to see why this is a problem though, care to explain? It is going to change the PCI layout of any virtual machines with a config file containing gfx_passthru="igd" and no pci config line. A Xen 4.7 user could add gfx_passthru="igd" to all her VM config files, because actually it does nothing unless an Intel graphic card is assigned to the VM. With this change she couldn't migrate their VMs from Xen 4.7 to Xen 4.8 safely because suddenly a new bridge appears. That said Xen 4.7 hasn't been released yet, so we could still change the intended behaviour. But it would require a bit of coordination (the qemu-xen tree in 4.7 is based on v2.4.1). > Also note that moving this to machine init nicely handles the fact that > the igd-isa-bridge is needed on 'pc' only, not on 'q35'. If you don't > want create the igd-isa-bridge in machine init, what is your alternative > suggestion to handle this? Maybe we could retain the check whether an Intel graphic card has been assigned?
WARNING: multiple messages have this Message-ID (diff)
From: Stefano Stabellini <stefano.stabellini@eu.citrix.com> To: Gerd Hoffmann <kraxel@redhat.com> Cc: igvt-g@ml01.01.org, xen-devel@lists.xensource.com, Eduardo Habkost <ehabkost@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>, Andrew Cooper <andrew.cooper3@citrix.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, qemu-devel@nongnu.org, Jan Beulich <JBeulich@novell.com>, Cao jin <caoj.fnst@cn.fujitsu.com>, vfio-users@redhat.com, Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <rth@twiddle.net> Subject: Re: [PATCH v3 11/11] igd: move igd-passthrough-isa-bridge creation to machine init Date: Thu, 7 Jan 2016 13:10:44 +0000 [thread overview] Message-ID: <alpine.DEB.2.02.1601071200210.13564@kaball.uk.xensource.com> (raw) In-Reply-To: <1452152339.6096.78.camel@redhat.com> CC'ing the Xen x86 maintainers On Thu, 7 Jan 2016, Gerd Hoffmann wrote: > Hi, > > > One thing I don't like about this is that it is going to skip the checks > > done in xen_pt_initfn. > > Hmm? Those checks are still done when you assign a igd ... Their failure doesn't affect the creation of the bridge. > > For example it is going to create the isa bridge, > > even if there is going to be an error loading the vga bios or if the > > device specified is not even an Intel graphic card. > > Creating the special igd-isa-bridge is no longer tied to actually > assigning a igd, but to the igd-passthru=on machine option being present > (and machine type being 'pc'). and machine type 'xenfv', unless I am mistaken? > xen_pt_initfn checks that igd-passthru=on is set in case it finds a igd > device is assigned, that will make sure the igd-isa-bridge is present. > > But, yes, you can create a igd-isa-bridge now even when not assigning a > igd device, either by specifying igd-passthru=on or using -device. I > fail to see why this is a problem though, care to explain? It is going to change the PCI layout of any virtual machines with a config file containing gfx_passthru="igd" and no pci config line. A Xen 4.7 user could add gfx_passthru="igd" to all her VM config files, because actually it does nothing unless an Intel graphic card is assigned to the VM. With this change she couldn't migrate their VMs from Xen 4.7 to Xen 4.8 safely because suddenly a new bridge appears. That said Xen 4.7 hasn't been released yet, so we could still change the intended behaviour. But it would require a bit of coordination (the qemu-xen tree in 4.7 is based on v2.4.1). > Also note that moving this to machine init nicely handles the fact that > the igd-isa-bridge is needed on 'pc' only, not on 'q35'. If you don't > want create the igd-isa-bridge in machine init, what is your alternative > suggestion to handle this? Maybe we could retain the check whether an Intel graphic card has been assigned?
next prev parent reply other threads:[~2016-01-07 13:11 UTC|newest] Thread overview: 132+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-01-05 11:41 [Qemu-devel] [PATCH v3 00/11] igd passthrough chipset tweaks Gerd Hoffmann 2016-01-05 11:41 ` Gerd Hoffmann 2016-01-05 11:41 ` [Qemu-devel] [PATCH v3 01/11] pc: wire up TYPE_IGD_PASSTHROUGH_I440FX_PCI_DEVICE for !xen Gerd Hoffmann 2016-01-05 11:41 ` Gerd Hoffmann 2016-01-05 11:41 ` [Qemu-devel] [PATCH v3 02/11] pc: remove has_igd_gfx_passthru global Gerd Hoffmann 2016-01-05 11:41 ` Gerd Hoffmann 2016-01-06 14:32 ` [Qemu-devel] [Xen-devel] " Stefano Stabellini 2016-01-06 14:32 ` Stefano Stabellini 2016-01-19 15:09 ` [Qemu-devel] " Eduardo Habkost 2016-01-19 15:09 ` Eduardo Habkost 2016-01-05 11:41 ` [Qemu-devel] [PATCH v3 03/11] pc: move igd support code to igd.c Gerd Hoffmann 2016-01-05 11:41 ` Gerd Hoffmann 2016-01-05 11:41 ` [Qemu-devel] [PATCH v3 04/11] igd: switch TYPE_IGD_PASSTHROUGH_I440FX_PCI_DEVICE to realize Gerd Hoffmann 2016-01-05 11:41 ` Gerd Hoffmann 2016-01-06 14:32 ` [Qemu-devel] " Stefano Stabellini 2016-01-06 14:32 ` Stefano Stabellini 2016-01-23 14:51 ` [Qemu-devel] " Eduardo Habkost 2016-01-23 14:51 ` Eduardo Habkost 2016-01-25 8:59 ` [Qemu-devel] " Gerd Hoffmann 2016-01-25 8:59 ` Gerd Hoffmann 2016-01-25 11:53 ` [Qemu-devel] " Stefano Stabellini 2016-01-25 11:53 ` Stefano Stabellini 2016-01-05 11:41 ` [Qemu-devel] [PATCH v3 05/11] igd: TYPE_IGD_PASSTHROUGH_I440FX_PCI_DEVICE: call parent realize Gerd Hoffmann 2016-01-05 11:41 ` Gerd Hoffmann 2016-01-06 14:41 ` [Qemu-devel] " Stefano Stabellini 2016-01-06 14:41 ` Stefano Stabellini 2016-01-06 15:45 ` [Qemu-devel] " Gerd Hoffmann 2016-01-06 15:45 ` Gerd Hoffmann 2016-01-19 15:13 ` [Qemu-devel] " Eduardo Habkost 2016-01-19 15:13 ` Eduardo Habkost 2016-01-20 9:10 ` [Qemu-devel] " Gerd Hoffmann 2016-01-20 9:10 ` Gerd Hoffmann 2016-01-23 14:52 ` [Qemu-devel] " Eduardo Habkost 2016-01-23 14:52 ` Eduardo Habkost 2016-01-05 11:41 ` [Qemu-devel] [PATCH v3 06/11] igd: use defines for standard pci config space offsets Gerd Hoffmann 2016-01-05 11:41 ` Gerd Hoffmann 2016-01-06 14:43 ` [Qemu-devel] " Stefano Stabellini 2016-01-06 14:43 ` Stefano Stabellini 2016-01-05 11:41 ` [Qemu-devel] [PATCH v3 07/11] igd: revamp host config read Gerd Hoffmann 2016-01-05 11:41 ` Gerd Hoffmann 2016-01-06 15:02 ` [Qemu-devel] " Stefano Stabellini 2016-01-06 15:02 ` Stefano Stabellini 2016-01-06 15:51 ` [Qemu-devel] " Gerd Hoffmann 2016-01-06 15:51 ` Gerd Hoffmann 2016-01-06 16:23 ` [Qemu-devel] [Xen-devel] " Stefano Stabellini 2016-01-06 16:23 ` Stefano Stabellini 2016-01-05 11:41 ` [Qemu-devel] [PATCH v3 08/11] igd: add q35 support Gerd Hoffmann 2016-01-05 11:41 ` Gerd Hoffmann 2016-01-05 11:41 ` [Qemu-devel] [PATCH v3 09/11] igd: move igd-passthrough-isa-bridge to igd.c too Gerd Hoffmann 2016-01-05 11:41 ` Gerd Hoffmann 2016-01-05 11:41 ` [Qemu-devel] [PATCH v3 10/11] igd: handle igd-passthrough-isa-bridge setup in realize() Gerd Hoffmann 2016-01-05 11:41 ` Gerd Hoffmann 2016-01-06 15:29 ` [Qemu-devel] " Stefano Stabellini 2016-01-06 15:29 ` Stefano Stabellini 2016-01-06 15:52 ` [Qemu-devel] " Gerd Hoffmann 2016-01-06 15:52 ` Gerd Hoffmann 2016-01-05 11:41 ` [Qemu-devel] [PATCH v3 11/11] igd: move igd-passthrough-isa-bridge creation to machine init Gerd Hoffmann 2016-01-05 11:41 ` Gerd Hoffmann 2016-01-06 15:36 ` [Qemu-devel] " Stefano Stabellini 2016-01-06 15:36 ` Stefano Stabellini 2016-01-07 7:38 ` [Qemu-devel] " Gerd Hoffmann 2016-01-07 7:38 ` Gerd Hoffmann 2016-01-07 13:10 ` Stefano Stabellini [this message] 2016-01-07 13:10 ` Stefano Stabellini 2016-01-07 15:50 ` [Qemu-devel] " Gerd Hoffmann 2016-01-07 15:50 ` Gerd Hoffmann 2016-01-08 11:20 ` Stefano Stabellini 2016-01-08 11:20 ` Stefano Stabellini 2016-01-08 12:12 ` [Qemu-devel] " Stefano Stabellini 2016-01-08 12:12 ` Stefano Stabellini 2016-01-08 12:32 ` Gerd Hoffmann 2016-01-08 12:32 ` Gerd Hoffmann 2016-01-08 12:38 ` [Qemu-devel] " Stefano Stabellini 2016-01-08 12:38 ` Stefano Stabellini 2016-01-05 13:07 ` [Qemu-devel] [PATCH v3 00/11] igd passthrough chipset tweaks Michael S. Tsirkin 2016-01-05 13:07 ` Michael S. Tsirkin 2016-01-28 19:35 ` [Qemu-devel] [vfio-users] " Alex Williamson 2016-01-28 19:35 ` Alex Williamson 2016-01-29 2:22 ` [Qemu-devel] [iGVT-g] " Kay, Allen M 2016-01-29 2:22 ` Kay, Allen M 2016-01-29 2:54 ` [Qemu-devel] " Alex Williamson 2016-01-29 2:54 ` Alex Williamson 2016-01-29 6:21 ` [Qemu-devel] " Jike Song 2016-01-29 6:21 ` Jike Song 2016-01-29 21:58 ` [Qemu-devel] " Kay, Allen M 2016-01-29 21:58 ` Kay, Allen M 2016-02-02 7:07 ` [Qemu-devel] " Tian, Kevin 2016-02-02 7:07 ` Tian, Kevin 2016-02-02 19:10 ` [Qemu-devel] " Kay, Allen M 2016-02-02 19:10 ` [iGVT-g] " Kay, Allen M 2016-02-02 19:37 ` [Qemu-devel] [iGVT-g] [vfio-users] " Alex Williamson 2016-02-02 19:37 ` Alex Williamson 2016-02-02 23:32 ` [Qemu-devel] " Kay, Allen M 2016-02-02 23:32 ` Kay, Allen M 2016-01-29 7:09 ` [Qemu-devel] " Gerd Hoffmann 2016-01-29 7:09 ` Gerd Hoffmann 2016-01-29 17:59 ` [Qemu-devel] " Alex Williamson 2016-01-29 17:59 ` Alex Williamson 2016-01-30 1:18 ` [Qemu-devel] [iGVT-g] " Kay, Allen M 2016-01-30 1:18 ` Kay, Allen M 2016-01-31 17:42 ` [Qemu-devel] " Alex Williamson 2016-01-31 17:42 ` Alex Williamson 2016-02-02 0:04 ` [Qemu-devel] " Kay, Allen M 2016-02-02 0:04 ` Kay, Allen M 2016-02-02 6:42 ` [Qemu-devel] [Xen-devel] " Tian, Kevin 2016-02-02 6:42 ` Tian, Kevin 2016-02-02 11:50 ` [Qemu-devel] " David Woodhouse 2016-02-02 11:50 ` David Woodhouse 2016-02-02 14:54 ` [Qemu-devel] " Alex Williamson 2016-02-02 14:54 ` Alex Williamson 2016-02-02 15:06 ` [Qemu-devel] " David Woodhouse 2016-02-02 15:06 ` David Woodhouse 2016-02-02 14:38 ` [Qemu-devel] " Alex Williamson 2016-02-02 14:38 ` Alex Williamson 2016-02-01 12:49 ` [Qemu-devel] " Gerd Hoffmann 2016-02-01 12:49 ` Gerd Hoffmann 2016-02-01 22:16 ` [Qemu-devel] " Alex Williamson 2016-02-01 22:16 ` Alex Williamson 2016-02-02 7:43 ` [Qemu-devel] [vfio-users] " Gerd Hoffmann 2016-02-02 7:43 ` Gerd Hoffmann 2016-02-02 7:01 ` [Qemu-devel] [iGVT-g] " Tian, Kevin 2016-02-02 7:01 ` [iGVT-g] " Tian, Kevin 2016-02-02 8:56 ` [Qemu-devel] [iGVT-g] [vfio-users] " Gerd Hoffmann 2016-02-02 8:56 ` Gerd Hoffmann 2016-02-02 16:31 ` [Qemu-devel] " Kevin O'Connor 2016-02-02 16:31 ` Kevin O'Connor 2016-02-02 16:49 ` [Qemu-devel] " Laszlo Ersek 2016-02-02 16:49 ` Laszlo Ersek 2016-02-02 20:18 ` [Qemu-devel] " Alex Williamson 2016-02-02 20:18 ` Alex Williamson 2016-02-03 6:08 ` [Qemu-devel] " Tian, Kevin 2016-02-03 6:08 ` Tian, Kevin
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