Re: FSGSBASE causing panic on 5.9-rc1

[Andy Lutomirski]

On Thu, Aug 20, 2020 at 6:43 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>
> On 19/08/20 23:25, Andy Lutomirski wrote:
> >         wrmsrl(MSR_KERNEL_GS_BASE, current->thread.gsbase);
> >         load_gs_index(svm->host.gs);
> >
> > Surely that should do load_gs_index() *before* wrmsrl().  But that's
> > not the problem at hand.
>
> The wrmsrl is writing the inactive GS base so the ordering between
> load_gs_index and wrmsrl(MSR_KERNEL_GS_BASE) should be irrelevant?

load_gs_index() sets the index between a pair of swapgs's -- it writes
the inactive base, too.

--Andy