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Subject: Re: [virtio-comment] [PATCH v1 1/8] admin: Add theory of operation for device migration
On Tue, Nov 07, 2023 at 03:57:29PM +0800, Zhu, Lingshan wrote: > > > On 11/7/2023 3:22 PM, Michael S. Tsirkin wrote: > > On Tue, Nov 07, 2023 at 12:05:12PM +0800, Jason Wang wrote: > > > > > > > One thing that you ignore is that, hypervisor can use what you > > > > > > > invented as a transport for VF, no? > > > > > > > > > > > > > No. by design, > > > > > It works like hypervisor traps the virito config and forwards it to admin > > > > > virtqueue and starts the device via device context. > > > > It needs more granular support than the management framework of device context. > > > It doesn't otherwise it is a design defect as you can't recover the > > > device context in the destination. > > > > > > Let me give you an example: > > > > > > 1) in the case of live migration, dst receive migration byte flows and > > > convert them into device context > > > 2) in the case of transporting, hypervisor traps virtio config and > > > convert them into the device context > > > > > > I don't see anything different in this case. Or can you give me an example? > > "trap virtio config" means "trap writes into virtio config" presumably? > > config can change itself without driver doing anything. Hypervisor > > can't trap it then. This is one of the problems with Lingshan's > > SUSPEND bit - what happens with these config changes in underspecified. > It should send a config interrupt and increase its generation. /me shrugs > By the way, is it buggy if a device suspend itself? > Is needs_reset better even not properly handled by virito driver NEEDS_RESET turned out not to be a great design. -- MST
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