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From: "Tian, Kevin" <kevin.tian@intel.com>
To: Stefano Stabellini <sstabellini@kernel.org>
Cc: "Lan, Tianyu" <tianyu.lan@intel.com>,
	"yang.zhang.wz@gmail.com" <yang.zhang.wz@gmail.com>,
	"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
	"Nakajima, Jun" <jun.nakajima@intel.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	"Dong, Eddie" <eddie.dong@intel.com>,
	"jbeulich@suse.com" <jbeulich@suse.com>,
	"anthony.perard@citrix.com" <anthony.perard@citrix.com>,
	"boris.ostrovsky@oracle.com" <boris.ostrovsky@oracle.com>,
	"ian.jackson@eu.citrix.com" <ian.jackson@eu.citrix.com>,
	Roger Pau Monne <roger.pau@citrix.com>
Subject: Re: Current PVH/HVMlite work and planning (was :Re: Discussion about virtual iommu support for Xen guest)
Date: Tue, 7 Jun 2016 05:48:54 +0000	[thread overview]
Message-ID: <AADFC41AFE54684AB9EE6CBC0274A5D15F891672@SHSMSX101.ccr.corp.intel.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1606031754260.2590@sstabellini-ThinkPad-X260>

> From: Stefano Stabellini
> Sent: Saturday, June 04, 2016 12:57 AM
> 
> > > >
> > > > How stable is the HVMLite today? Is it already in production usage?
> > > >
> > > > Wonder whether you have some detail thought how full PCI root complex
> > > > emulation will be done in Xen (including how to interact with Qemu)...
> > >
> > > I haven't looked into much detail regarding all this, since as I said, it's
> > > still a little bit far away in the PVH/HVMlite roadmap, we have more
> > > pressing issues to solve before getting to the point of implementing
> > > PCI-passthrough. I expect Xen is going to intercept all PCI accesses and is
> > > then going to forward them to the ioreq servers that have been registered
> > > for that specific config space, but this of course needs much more thought
> > > and a proper design document.
> > >
> > > > As I just wrote in another mail, if we just hit for HVM first, will it work if
> > > > we implement vIOMMU in Xen but still relies on Qemu root complex to
> > > > report to the guest?
> > >
> > > This seems quite inefficient IMHO (but I don't know that much about all this
> > > vIOMMU stuff). If you implement vIOMMU inside of Xen, but the PCI root
> > > complex is inside of Qemu aren't you going to perform quite a lot of jumps
> > > between Xen and QEMU just to access the vIOMMU?
> > >
> > > I expect something like:
> > >
> > > Xen traps PCI access -> QEMU -> Xen vIOMMU implementation
> > >
> >
> > I hope the role of Qemu is just to report vIOMMU related information, such
> > as DMAR, etc. so guest can enumerate the presence of vIOMMU, while
> > the actual emulation is done by vIOMMU in hypervisor w/o going through
> > Qemu.
> >
> > However just realized even for above purpose, there's still some interaction
> > required between Qemu and Xen vIOMMU, e.g. register base of vIOMMU and
> > devices behind vIOMMU are reported thru ACPI DRHD which means Xen vIOMMU
> > needs to know the configuration in Qemu which might be dirty to define such
> > interfaces between Qemu and hypervisor. :/
> 
> PCI accesses don't need to be particularly fast, they should not be on
> the hot path.
> 
> How bad this interface between QEMU and vIOMMU in Xen would look like?
> Can we make a short list of basic operations that we would need to
> support to get a clearer idea?

Below is a quick thought of basic operations between vIOMMU and a PCI 
root-complex, if they are not putting together:
(come from VT-d spec, section 8, "BIOS Consideration")

1) vIOMMU reports its presence including capabilities to root-complex:
	- interrupt remapping, ATS, etc.
	- type of devices (virtual, PV, passthrough)... (???TBD)

2) root-complex notifies vIOMMU about:
	- base of vIOMMU registers (DRHD)
	- devices attached to this vIOMMU (DRHD)
		* dynamic update due to hotplug or PCI resource rebalancing

3) Additionally as I mentioned in another thread, Qemu need to query
vIOMMU whether a virtual DMA should be blocked, if vIOMMU for virtual
devices are also put in Xen

Other BIOS structures (ATS, RMRR, hotplug, etc.) are optional so I haven't
thought carefully now. They may require additional interactions if required.

Thanks
Kevin
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  reply	other threads:[~2016-06-07  5:48 UTC|newest]

Thread overview: 86+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-05-26  8:29 Discussion about virtual iommu support for Xen guest Lan Tianyu
2016-05-26  8:42 ` Dong, Eddie
2016-05-27  2:26   ` Lan Tianyu
2016-05-27  8:11     ` Tian, Kevin
2016-05-26 11:35 ` Andrew Cooper
2016-05-27  8:19   ` Lan Tianyu
2016-06-02 15:03     ` Lan, Tianyu
2016-06-02 18:58       ` Andrew Cooper
2016-06-03 11:01         ` Current PVH/HVMlite work and planning (was :Re: Discussion about virtual iommu support for Xen guest) Roger Pau Monne
2016-06-03 11:21           ` Tian, Kevin
2016-06-03 11:52             ` Roger Pau Monne
2016-06-03 12:11               ` Tian, Kevin
2016-06-03 16:56                 ` Stefano Stabellini
2016-06-07  5:48                   ` Tian, Kevin [this message]
2016-06-03 11:17         ` Discussion about virtual iommu support for Xen guest Tian, Kevin
2016-06-03 13:09           ` Lan, Tianyu
2016-06-03 14:00             ` Andrew Cooper
2016-06-03 13:51           ` Andrew Cooper
2016-06-03 14:31             ` Jan Beulich
2016-06-03 17:14             ` Stefano Stabellini
2016-06-07  5:14               ` Tian, Kevin
2016-06-07  7:26                 ` Jan Beulich
2016-06-07 10:07                 ` Stefano Stabellini
2016-06-08  8:11                   ` Tian, Kevin
2016-06-26 13:42                     ` Lan, Tianyu
2016-06-29  3:04                       ` Tian, Kevin
2016-07-05 13:37                         ` Lan, Tianyu
2016-07-05 13:57                           ` Jan Beulich
2016-07-05 14:19                             ` Lan, Tianyu
2016-08-17 12:05                             ` Xen virtual IOMMU high level design doc Lan, Tianyu
2016-08-17 12:42                               ` Paul Durrant
2016-08-18  2:57                                 ` Lan, Tianyu
2016-08-25 11:11                               ` Jan Beulich
2016-08-31  8:39                                 ` Lan Tianyu
2016-08-31 12:02                                   ` Jan Beulich
2016-09-01  1:26                                     ` Tian, Kevin
2016-09-01  2:35                                     ` Lan Tianyu
2016-09-15 14:22                               ` Lan, Tianyu
2016-10-05 18:36                                 ` Konrad Rzeszutek Wilk
2016-10-11  1:52                                   ` Lan Tianyu
2016-11-23 18:19                               ` Edgar E. Iglesias
2016-11-23 19:09                                 ` Stefano Stabellini
2016-11-24  2:00                                   ` Tian, Kevin
2016-11-24  4:09                                     ` Edgar E. Iglesias
2016-11-24  6:49                                       ` Lan Tianyu
2016-11-24 13:37                                         ` Edgar E. Iglesias
2016-11-25  2:01                                           ` Xuquan (Quan Xu)
2016-11-25  5:53                                           ` Lan, Tianyu
2016-10-18 14:14                             ` Xen virtual IOMMU high level design doc V2 Lan Tianyu
2016-10-18 19:17                               ` Andrew Cooper
2016-10-20  9:53                                 ` Tian, Kevin
2016-10-20 18:10                                   ` Andrew Cooper
2016-10-20 14:17                                 ` Lan Tianyu
2016-10-20 20:36                                   ` Andrew Cooper
2016-10-22  7:32                                     ` Lan, Tianyu
2016-10-26  9:39                                       ` Jan Beulich
2016-10-26 15:03                                         ` Lan, Tianyu
2016-11-03 15:41                                         ` Lan, Tianyu
2016-10-28 15:36                                     ` Lan Tianyu
2016-10-18 20:26                               ` Konrad Rzeszutek Wilk
2016-10-20 10:11                                 ` Tian, Kevin
2016-10-20 14:56                                 ` Lan, Tianyu
2016-10-26  9:36                               ` Jan Beulich
2016-10-26 14:53                                 ` Lan, Tianyu
2016-11-17 15:36                             ` Xen virtual IOMMU high level design doc V3 Lan Tianyu
2016-11-18 19:43                               ` Julien Grall
2016-11-21  2:21                                 ` Lan, Tianyu
2016-11-21 13:17                                   ` Julien Grall
2016-11-21 18:24                                     ` Stefano Stabellini
2016-11-21  7:05                               ` Tian, Kevin
2016-11-23  1:36                                 ` Lan Tianyu
2016-11-21 13:41                               ` Andrew Cooper
2016-11-22  6:02                                 ` Tian, Kevin
2016-11-22  8:32                                 ` Lan Tianyu
2016-11-22 10:24                               ` Jan Beulich
2016-11-24  2:34                                 ` Lan Tianyu
2016-06-03 19:51             ` Is: 'basic pci bridge and root device support. 'Was:Re: Discussion about virtual iommu support for Xen guest Konrad Rzeszutek Wilk
2016-06-06  9:55               ` Jan Beulich
2016-06-06 17:25                 ` Konrad Rzeszutek Wilk
2016-08-02 15:15     ` Lan, Tianyu
2016-05-27  8:35   ` Tian, Kevin
2016-05-27  8:46     ` Paul Durrant
2016-05-27  9:39       ` Tian, Kevin
2016-05-31  9:43   ` George Dunlap
2016-05-27  2:26 ` Yang Zhang
2016-05-27  8:13   ` Tian, Kevin

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