FreeBSD 12.1 i386 on Hyper-V Fails to Mount Root

[Wei Hu]

> -----Original Message-----
> From: Konstantin Belousov <kostikbel at gmail.com>
> Sent: Monday, May 17, 2021 1:47 PM
> To: Wei Hu <weh at microsoft.com>
> Cc: Harry Schmalzbauer <freebsd at omnilan.de>; Chris Knight
> <stryqx at gmail.com>; freebsd-virtualization at freebsd.org
> Subject: Re: FreeBSD 12.1 i386 on Hyper-V Fails to Mount Root
> 
> On Mon, May 17, 2021 at 04:12:20AM +0000, Wei Hu wrote:
> > Copy Kib  who was the author of PTI and other relate patches.
> >
> > This looks to be caused by Meltdown and Spectre mitigation patches
> > which were checked into head couple years ago. See this link for details about
> these patches:
> > https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwiki
> > .freebsd.org%2FSpeculativeExecutionVulnerabilities&data=04%7C01%7C
> >
> weh%40microsoft.com%7Cd7b33cd5fc774c88310008d918f744c4%7C72f988bf
> 86f14
> >
> 1af91ab2d7cd011db47%7C1%7C0%7C637568272592647219%7CUnknown%7
> CTWFpbGZsb
> >
> 3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%
> 3D%
> >
> 7C1000&sdata=5HjRc67IiHlrpR5bgWwJq9opMwBKudlHJpElsDZkS4A%3D&
> amp;re
> > served=0
> >
> > The amd64  patches also caused problems on Hyper-V (triple fault) when
> > vmbus and other HyperV drivers (netvsc, storvsc etc) were loaded
> > separately. The workaround for this on amd64 is either build these
> > Hyper-V modules into the kernel or completely disable mitigation by
> > setting vm.pmap.pti="0" in /boot/loader.conf in the affect FreeBSD guests.
> >
> For amd64 I posted the patch to supposedly fix the issue, you did not
> responded.
> 
I am sorry I might have missed your review request. Would you please let me 
know the link to the patch or the commit if you already have checked in? I will
need to test and inform the parties who got affected. 

For the issue on i386, any plan to fix it.

Thanks,
Wei