RE: [Xen-devel] frontend and backend devices and differenttypes of hw - pci for example

["Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>]

> While I'm on the subject, I'd personally like to see guests 
> granted IO access slightly differently.  There are two ways 
> to grant IO access on x86: change the IOPL (giving the guest 
> access to all IO ports) or set IO bits in the TSS (giving 
> fine grained control).  The problem with the latter is that guest
> *apps* will be able to access the hardware; essentially x86 
> gives you coarse grained control and ring-level protection, 
> or vice-versa.
> 
> Since people often like to partition their systems using Xen, 
> I don't really like giving apps easy access to the hardware 
> in this way.  I'd like to have the option of trapping IO port 
> writes in Xen and verifying the guest's IO privileges in 
> software, then emulating the write. 

That's how it works in -unstable today...

Ian

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