Re: Installing WinPV drivers on Windows 2019

[Jan Bakuwel <jan.bakuwel@xxxxxxxxx>]

Hi Paul,

On 9/06/20 7:27 pm, Paul Durrant wrote:
> > -----Original Message-----
> > From: Jan Bakuwel <jan.bakuwel@xxxxxxxxx>
> > Sent: 09 June 2020 03:33
> > To: paul@xxxxxxx; win-pv-devel@xxxxxxxxxxxxxxxxxxxx
> > Subject: Re: Installing WinPV drivers on Windows 2019
> >
> > Hi Paul,
> > > Hi Jan,
> > >
> > >     Oddly the summary analysis below fingers the network driver but when I pull 
> > > the dump into windbg,
> > it clearly points at a stack overflow in a thread starting in xenvbd...
> >
> > I'm not familiar with Windows driver debugging but trust you when you
> > say it is :-)
> >
> > Any suggestions where we can go from here?
> Hi Jan,
>
> I think you are hitting a bug in Windows itself that was worked around by this 
> commit in XENVIF:
>
> https://xenbits.xen.org/gitweb/?p=pvdrivers/win/xenvif.git;a=commit;h=4f85d00477b0931d4367a34de4f84d54b0f04d4e
>
> ---
> Replace uses of MmAllocatePagesForMdlEx in __AllocatePage
>
> Windows appears to have an edge case bug in which zeroing
> memory using MmAllocatePAgesForMdlEx (which in Win 10 1803
> happens even if you specify MM_DONT_ZERO_ALLOCATION) can cause
> a BSOD 139 1e.
>
> This commit uses MmAllocateContinguousMemorySpecifyCache
> to allocate memory instead, then builds and Mdl to wrap
> it up.
>
> __AllocatePages is left unchanged (as we don't want
> to allocate multiple contiguous pages).  This issue
> has not been seen outside of xenvif calls to
> __AllocatePage and we expect a fix to the underlying
> Windows problem in the near future
>
> Signed-off-by: Ben.Chalmers <ben.chalmers@xxxxxxxxxx>
> ---
>
> Firstly, is your installation fully updated?
That depends on Microsoft :-) ... the server is set to auto update.

I just hit "Check for Updates" and the server pulled in three updates: 
one for Windows Defender, one KB4551853 and one for Adobe Flash, none of 
them related.
> If so then it appears Microsoft have *still* not fixed this, despite it being 
> identified in 2018, in which case I will clone the above commit into XENVBD and 
> also amend any other drivers using MmAllocatePagesForMdlEx() with that option.
I think it's safe to conclude that Microsoft indeed has not fixed this. 
Not really surprising, eh?
Many thanks for your help, looking forward to the new drivers.

kind regards,
Jan