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Re: [win-pv-devel] Xen windows PV driver questions


From: gaowei (Y) [mailto:gaowei17@xxxxxxxxxx] 
Sent: 17 May 2016 10:10
To: Paul Durrant; Paul Durrant
Cc: win-pv-devel@xxxxxxxxxxxxxxxxxxxx
Subject: Xen windows PV driver questions

Hello Paul
This is Wayne Gao from Huawei. Nice to talk with you. I have couples of 
technical questions regarding with Xen windows PV drivers.
Could you please take a time to help? Really appreciate your help!~
1. May I know if the latest windows PV open source code can pass the WHCK tests 
very stable and get driver signed?

> Yes. The XenServer PV drivers are based on this source with only small 
> compatibility patches.

2. From the home page, I see there is a plan to join in windows update. May I 
know how this is going on? Any plan to make it happen. Another approach is that 
Microsoft allow semiconductor company deliver inbox driver. Do we have this 

> The XenServer branded drivers are currently live on Windows Update so if 
> you're VM has the appropriate PV device then these drivers will download and 
> install. XenProject branded drivers will not go onto Windows Update.

3. I saw in current win PV driver, we add one new driver xencrsh.sys to 
complete the dump. But windows actually has the function just reuse the 
original storport miniport driver to complete the dump. Microsoft sample 
storachi driver did this way too. May I know what is special reason that we 
choose add new driver?

> The crash kernel environment is quite different to a normal kernel 
> environment. The xencrsh driver is actually linked into the normal xenvbd 
> storport driver but only activates when in the crash kernel environment. It 
> then activates as the storage driver and uses its own private interfaces to 
> talk to Xen and the PV backend (since the normal xenbus provided APIs are not 
> available).

4. I saw there is one storage filter driver that is above the storport. 
Microsoft WHCK document used to mention MS do not like any filter above 
storport. May I know what is special reason that we choose add filter drivers 
into the architecture?

> There is a filter driver called xendisk that sits above the storport PDOs. It 
> serves only to intercept the IRPs necessary to support trim/discard. Newer 
> versions of storport support trim/discard directly but the drivers cannot 
> make use of newer storport as they are designed to function on older versions 
> of Windows.
Currently, we saw all developers are from Citrix. May I know if Huawei can 
contribute on this project too?

> Absolutely. Contributions have already been made by Invisible Things Labs and 
> Amazon so I'd be happy to review contributions from Huawei.
> Cheers,
>   Paul
Thank you so much again for your help!~
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