Re: [Xen-devel] [PATCH] x86-64: clear DF for kernel when forwarding syscall

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

>>> Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> 06/25/07 12:02 AM >>>
>On 24/6/07 11:58, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:
>
>> I had sent a mail to that effect (at least I think I had) - on x86-64, this
>> may
>> be the preferred way (at least for the !XEN_COMPAT case), but the i386
>> kernel has to remain runnable on 32-bit Xen, and doing gp-fault-recoverable
>> MSR accesses doesn't buy us anything in terms of not needing specialized
>> Xen code (i.e. if we need special Xen code, we can equally well do
>> hypercalls).
>> For that reason, at this point I implemented both access methods, but haven't
>> got around yet to make the kernel side use them.
>
>The only problem is it probably requires an entirely new top-level hypercall
>because it's not going to fit into the constraints of the existing
>callback_op(). 

Why? The flags mask can be put in the offset/address field, and there's nothing
preventing the guest from putting NULL or even garbage in the selector field on
32-bits.

Jan

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel