Re: selftests/x86/fsgsbase_64 test problem

[H. Peter Anvin]

On 01/26/18 11:46, Andy Lutomirski wrote:
> 
> Under QEMU TCG, gs stays equal to 1.  On native or KVM, on Skylake, it
> changes to 0.
> 
> On KVM or native, I do not observe do_debug getting called with %gs ==
> 1.  On TCG, I do.  I don't think that's precisely the problem that's
> causing the test to fail, since the test doesn't use TF or ptrace, but
> I wouldn't be shocked if it's related.
> 
> hpa, any insight?
> 
> (NB: if you want to play with this as I've described it, you may need
> to make invalid_selector() in ptrace.c always return false.  The
> current implementation is too strict and causes problems.)
> 

Looking at it.  I want to grok this in the general context of fsgsbase
as well, of course.

	-hpa