[Xen-devel] Re: [RFC, PATCH 8/24] i386 Vmi syscall assembly

[Chris Wright <chrisw@xxxxxxxxxxxx>]

* Zachary Amsden (zach@xxxxxxxxxx) wrote:
> These changes are sufficient to glue the Linux low level entry points to
> hypervisor event injection by emulating the native processor exception
> frame interface.

There's a bit more going on in the Xen changes to entry.S.  The STI/CLI
abstraction definitely gets partway there.  Then there's some bits that
use (in your terms) __STI, __CLI.  It's in code that's a pure addition
so it's tempting to simply make a mechanism for the additions, but it's a bit
too intertwined to just separate that code, as there's calls from core
entry.S into the Xen additions.

> N.B. Sti; Sysexit is a required abstraction, as the STI instruction implies
> holdoff of interrupts, which is destroyed by any NOP padding.

Or just disable systenter ;-)  Random question...do you support systenter?
Sounds slower than int80, since it should require 3->0->1->0->3 transitions.
Just idly curious if you've done benchmarks to see the difference.

thanks,
-chris

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