Re: [PATCH v10 00/18] Enable FSGSBASE instructions

[Sasha Levin]

On Sun, May 10, 2020 at 05:50:28PM -0700, Andi Kleen wrote:
> > So this is a check that checks if you're running in user mode if
> > you have a debug trap with single step, but somehow it triggered
> > for a user segment.
> >
> > Probably the regs got corrupted.
> >
> > Sasha, I suspect you're missing a mov %rsp,%rdi somewhere in the
> > debug entry path that sets up the regs argument for the C code.
>
> ... Ah never mind. Thomas has a better explanation.

FWIW, this series was heavily tested for the past few months to the
point that we're comfortable in enabling it for 3rd party users on
Azure:
https://bugs.launchpad.net/ubuntu/+source/linux-azure/+bug/1877425.

--
Thanks,
Sasha