Re: Is espfix64's double-fault thing OK on Xen?

From: H. Peter Anvin
Date: Mon Jul 14 2014 - 18:23:32 EST

On 07/14/2014 02:35 PM, Andy Lutomirski wrote:
> Presumably the problem is here:
> ENTRY(xen_iret)
> pushq $0
> 1: jmp hypercall_iret
> ENDPATCH(xen_iret)
> This seems rather unlikely to work on the espfix stack.
> Maybe espfix64 should be disabled when running on Xen and Xen should
> implement its own espfix64 in the hypervisor.

Perhaps the first question is: is espfix even necessary on Xen? How
does the Xen PV IRET handle returning to a 16-bit stack segment?


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