From: "Tian, Kevin" <kevin.tian@intel.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>,
"Lan, Tianyu" <tianyu.lan@intel.com>,
Jan Beulich <JBeulich@suse.com>,
"yang.zhang.wz@gmail.com" <yang.zhang.wz@gmail.com>,
"Nakajima, Jun" <jun.nakajima@intel.com>,
Stefano Stabellini <sstabellini@kernel.org>
Cc: "anthony.perard@citrix.com" <anthony.perard@citrix.com>,
"xuquan8@huawei.com" <xuquan8@huawei.com>,
"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
"ian.jackson@eu.citrix.com" <ian.jackson@eu.citrix.com>,
Roger Pau Monne <roger.pau@citrix.com>
Subject: Re: Xen virtual IOMMU high level design doc V3
Date: Tue, 22 Nov 2016 06:02:14 +0000 [thread overview]
Message-ID: <AADFC41AFE54684AB9EE6CBC0274A5D18E027AB5@SHSMSX101.ccr.corp.intel.com> (raw)
In-Reply-To: <f5fe2314-8c9b-ac52-1b6d-807bc82dc517@citrix.com>
> From: Andrew Cooper [mailto:andrew.cooper3@citrix.com]
> Sent: Monday, November 21, 2016 9:41 PM
>
> On 17/11/16 15:36, Lan Tianyu wrote:
> > 3.2 l2 translation
> > 1) For virtual PCI device
> > Xen dummy xen-vIOMMU in Qemu translates IOVA to target GPA via new
> > hypercall when DMA operation happens.
> >
> > When guest triggers a invalidation operation, there maybe in-fly DMA
> > request for virtual device has been translated by vIOMMU and return back
> > Qemu. Before vIOMMU tells invalidation completed, it's necessary to make
> > sure in-fly DMA operation is completed.
> >
> > When IOMMU driver invalidates IOTLB, it also will wait until the
> > invalidation completion. We may use this to drain in-fly DMA operation
> > for virtual device.
> >
> > Guest triggers invalidation operation and trip into vIOMMU in
> > hypervisor to flush cache data. After this, it should go to Qemu to
> > drain in-fly DMA translation.
> >
> > To do that, dummy vIOMMU in Qemu registers the same MMIO region as
> > vIOMMU's and emulation part of invalidation operation in Xen hypervisor
> > returns X86EMUL_UNHANDLEABLE after flush cache. MMIO emulation part is
> > supposed to send event to Qemu and dummy vIOMMU get a chance to starts a
> > thread to drain in-fly DMA and return emulation done.
> >
> > Guest polls IVT(invalidate IOTLB) bit in the IOTLB invalidate register
> > until it's cleared after triggering invalidation. Dummy vIOMMU in Qemu
> > notifies hypervisor drain operation completed via hypercall, vIOMMU
> > clears IVT bit and guest finish invalidation operation.
>
> Having the guest poll will be very inefficient. If the invalidation
> does need to reach qemu, it will be a very long time until it
> completes. Is there no interrupt based mechanism which can be used?
> That way the guest can either handle it asynchronous itself, or block
> waiting on an interrupt, both of which are better than having it just
> spinning.
>
VT-d spec supports both poll and interrupt modes, and it's decided
by guest IOMMU driver. Not say that this design requires guest to
use poll mode. I guess Tianyu uses as an example flow.
Thanks
Kevin
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next prev parent reply other threads:[~2016-11-22 6:02 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
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 [this message]
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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