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[Xen-devel] xm block-attach DomID tap:aio:/...

Hi folks,

I meet a problem when developing windows PV drivers for Xen. Now my drivers can support adding a 'file' type backend media as a VBD device using 'xm block-attach' command. With the same code, 'xm block-attach' a 'tap:aio' type backend media cannot works fine on my PV drivers. But if I add a 'file' type backend media to windows VM and set set it to 'tap:aio' type, it works fine. Since my driver didn't get WHQL digital signature, when adding a new device VM, windows will pops up a 'Find new hardware' dialog to install drivers for it even there is a device object represents for it. When installing driver for new storage class device, windows PnP manager will remove the device object and add a new one represents for the new device. In this progress, I will set device backend state to XenbusStateClosing->XenbusStateClosed ->XenbusStateInitWait and then reinitialize the device. If it's a 'file' type, all these progress works fine, but it's a 'type:aio' type, my drivers cannot get any response from ring buffer for Read/Write scsi command.

So does anybody can give me some brief guide on difference between 'file' type and 'tap:aio' type as a backend media for a frontend PV drivers? And I want to confirm that a 'tap:aio' type backend can work well when backend state changed as XenbusStateInitWait->XenbusStateConnected-> XenbusStateClosing->XenbusStateClosed ->XenbusStateInitWait->XenbusStateConnected. I know that a 'file' type backend is Yes, I think 'tap:aio' type is Yes either, just want to conform.

James, any suggestion?

BTW, I use OVM 2.1.2 based on Xen 3.1 series.

Merry Christmas and Happy New Year!


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