Re: [Xen-devel] [PATCH v4 0/3] x86: modify_ldt improvement, test, and config option

From: Boris Ostrovsky
Date: Tue Jul 28 2015 - 13:12:08 EST


On 07/28/2015 01:07 PM, Andy Lutomirski wrote:
On Tue, Jul 28, 2015 at 9:30 AM, Andrew Cooper
<andrew.cooper3@xxxxxxxxxx> wrote:
I suspect that the set_ldt(NULL, 0) call hasn't reached Xen before
xen_free_ldt() is attempting to nab back the pages which Xen still has
mapped as an LDT.

I just instrumented it with yet more LSL instructions. I'm pretty
sure that set_ldt really is clearing at least LDT entry zero.
Nonetheless the free_ldt call still oopses.


Yes, I added some instrumentation to the hypervisor and we definitely set LDT to NULL before failing.

-boris
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