On 04/13/2015 08:57 PM, Jan Kiszka wrote:
On 2015-04-13 19:48, Avi Kivity wrote:
I think that Xen does (or did) something along the lines of disabling
IST usage (by playing with the descriptors in the IDT) and then
re-enabling them when exiting to userspace.
So we would reuse that active stack for the current IST users until
then.
Yes.
But I bet there are subtle details that prevent a simple switch at
IDT level. Hmm, no low-hanging fruit it seems...
For sure. It's not insurmountable, but fairly hard.
[17] http://thread.gmane.org/gmane.comp.emulators.kvm.devel/26712/
That thread proposed the complete IST removal. But, given that we still
have it 7 years later,
Well, it's not as if a crack team of kernel hackers was laboring night
and day to remove it, but...
I suppose that was not very welcome in general.
Simply removing it is impossible, or an NMI happening immediately after
SYSCALL will hit user-provided %rsp.
Thanks,
Jan
PS: For the Jailhouse readers: we don't use IST.
You don't have userspace, yes? Only guests?
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
