Re: [Xen-devel] Changing semantics of ioperm() on Xen x86-64?

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 18 Apr 2006, at 22:50, Anthony Liguori wrote:

> As part of the Xen x86-64 Linux port, we've changed the ioperm() 
> syscall to always modify the IOPL instead of actually modifying the IO 
> bitmap in the TSS like we do on x86-32.  Is there a particular reason 
> for doing this?
> I'm completely guessing here that this may allow us to avoid changing 
> the TR when changing from user/kernel mode but that doesn't seem like 
> that huge of a gain.
> I don't expect that there are many apps that would rely on using 
> ioperm to restrict access to only certain ranges of ports so I don't 
> think this is a security problem but it still is a little 
> discomforting.
As Ian said, x86/64 port took an old snap of the i386 port and has gone 
stale in quite a few ways. It needs some maintenance TLC. i386 did the 
same thing with ioperm() until io bitmap support was added to Xen.
 -- Keir


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