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Re: [Xen-devel] [PATCH 3/2] x86/desc: Drop __HYPERVISOR_CS32

On 09.08.2019 14:39, Andrew Cooper wrote:
Xen, being 64bit only these days, has no use for a 32bit Ring 0 code segment.

Delete __HYPERVISOR_CS32 and remove it from the GDTs.  Also delete
__HYPERVISOR_CS64 and use __HYPERVISOR_CS uniformly.

Long, long ago we've been considering doing this. Agreed,
nothing has surfaced to actually use it, but I wouldn't
subscribe to "has no use": We will need it if we ever want
to be able to run on 32-bit EFI _and_ invoke runtime
services there. Back then through the consideration against
dropping it was that we may want to invoke 32-bit BIOS
services (PCI, VGA) from the hypervisor.

Of course it wouldn't be terribly difficult to re-instate
these selectors / descriptors, but still. Nevertheless, if
you're convinced of the move despite the remarks above ...

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Acked-by: Jan Beulich <jbeulich@xxxxxxxx>


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