FreeBSD 12.1 i386 on Hyper-V Fails to Mount Root

[Konstantin Belousov]

On Mon, May 17, 2021 at 06:33:19AM +0000, Wei Hu wrote:
> > -----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. 

It was mailed for you after your query, then I pinged you several times.
Anyway, look at and try https://reviews.freebsd.org/D30310

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