On Fri, Feb 04, 2022 at 03:13:52PM +0100, Jan Beulich wrote:
> On 04.02.2022 15:08, Thomas Gleixner wrote:
> > On Fri, Feb 04 2022 at 10:23, Jan Beulich wrote:
> >> On 30.11.2021 12:09, Jan Beulich wrote:
> >>> I think it is b968e84b509d ("x86/iopl: Fake iopl(3) CLI/STI usage")
> >>> which uncovered an issue with get_desc() trying to access the GDT, as
> >>> introduced by 670f928ba09b ("x86/insn-eval: Add utility function to
> >>> get segment descriptor"). When running in a PV domain under Xen, the
> >>> (hypervisor's) GDT isn't accessible; with UMIP enabled by Xen even
> >>> SGDT wouldn't work, as the kernel runs in ring 3.
> >>>
> >>> There's currently no hypercall to retrieve a descriptor from the GDT.
> >>> It is instead assumed that kernels know where their present GDT
> >>> lives. Can the native_store_gdt() be replaced there, please?
> >>>
> >>> For context (I don't think it should matter much here) I'm observing
> >>> this with the kernel put underneath a rather old distro, where
> >>> hwclock triggers this path.
> >>
> >> I'd like to note that the issue still exists in 5.16.
> >
> > I'd like to note, that I've seen no patches to that effect.
>
> I could have worded it that way as well, yes.
Hi Jan, I am sorry I missed your email. I'll look at the issue you
describe and get back to you.
Thanks and BR,
Ricardo
