Re: [Xen-devel] Hypercalls in Intel-VT

["Ashish Bijlani" <ashish.bijlani@xxxxxxxxx>]

that means dom0 doesn't make trap to ring 0 root VMX mode for privileged operations like updating cr3?

On 10/26/07, Dong, Eddie < eddie.dong@xxxxxxxxx> wrote:

DOm0 works in ring 1 root VMX mode. Anyway can switch from ring 1 to ring 0 can be used for accessing privileged resource such as INT xx, or thru exception like I/O.

 

But HVM works in non root VMX mode though ring=0, so you need to switch from non root VMX mode to root VMX mode to access privileged resource. VM Exit is the only way to do this.

---

From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Ashish Bijlani
Sent: 2007年10月26日 9:14
To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-devel] Hypercalls in Intel-VT

how does dom0 on intel-vt gets privileges to access the hardware devices? i mean does it get these privileges through superpages?

On 10/25/07, Cui, Dexuan <dexuan.cui@xxxxxxxxx> wrote:

> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx [mailto: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Ashish Bijlani
> Sent: 2007年10月26日 8:20
> To: xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-devel] Hypercalls in Intel-VT

>
> could there be a way to make a transition into xen without a vmexit upon executing an iret inside a guest os krnl?
I think we are talking about VMX guest -- the answer it NO...  For an VMX guest to return to Xen, a VMexit is a must. You can refert to Intel Software Developer Manual 3B for details.

-- Dexuan

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