Re: XENFEAT_supervisor_mode_kernel ???

[Mukesh Rathor <mukesh.rathor@oracle.com>]

Oh, cool. I was looking at syscalls on PV x86_64 guests, and one of my 
thoughts was running in HVM mode but do all MMU stuff using hypercalls like 
PV. Other than having to change the hyp domain create portions, setting things 
up, is there a technical reason it can't be done today... thanks, Mukesh

Keir Fraser wrote:
> On 20/11/08 22:42, "Mukesh Rathor" <mukesh.rathor@oracle.com> wrote:
> 
>> I'm trying ot figure out what that's all about? I see in 64 PV domU, it's
>> being checked prior to returning from syscall.  On the xen side, I see it tied
>> to supervisor_mode_kernel, but the only info I find is changelog comment which
>> suggests it's purpose is to allow dom0 run in ring 0... So why the check in a
>> domU kernel?
> 
> It's useful if the hypervisor runs the guest kernel in ring 0. Current Xen
> doesn't do that, but in future we may run 64-bit PV guests in HVM context as
> that may actually be faster.
> 
>  -- Keir
>