Re: [Xen-devel] Ring3 Hypercalls from HVM DomU

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2011-12-05 at 06:23 +0000, Zhang, Xiantao wrote:
> That is because âint $0x92â only switch the context to guestâs IDT
> instead of hypervisorâs IDT by default.

"by default"? Is there some mechanism by which an int instruction in
non-root mode can cause a vmexit to a host IDT entry instead of the
guest IDT? I didn't see it based on a quick skim of relevant chapters of
the SDM.

Ian.

> 
> Xiantao
> 
>  
> 
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Srujan
> Kotikela
> Sent: Saturday, December 03, 2011 4:52 AM
> To: xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-devel] Ring3 Hypercalls from HVM DomU
> 
>  
> 
> Hi,
> 
>  
> 
> 
> I have created hypercalls that can be invoked from ring-3 by setting
> the ring-3 gate in xen. This works fine when I invoke the hypercall
> from Dom0. I want to invoke the same from a HVM DomU. But I keep
> getting the segmentation fault when I invoke the ring3_hyperacall from
> HVM DomU. Any ideas?
> 
> The setting up gate is as follows:
> _set_gate(idt_table+0x92, 14, 3, &hypercall);
> 
> 
> 
> The hypercall invoking code looks like this:
> int ring3_hypercall(unsigned long va, int command)
> {
>     int ret;
> 
>     asm("int $0x92" : "=a"(ret) : "a"(40), "b"(va), "c"(command));
>     
>     return ret;
> }
> 
> ~ SDK
> 
> 



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