Re: [Xen-devel] PRIVCMD in HVM DomU

[Srujan Kotikela <ksrujandas@xxxxxxxxx>]

Hi,

I am using 2.6.18 kernel. I am going to try with a newer kernel (>= 2.6.36.7). 

Meanwhile I was looking at the following code in tools/firmware/hvmloader/hypercall.h

 44 #define _hypercall0(type, name)                                         \

 45 ({                                                                      \
 46         long __res;                                                     \

 47         asm volatile (                                                  \
 48                 "call "hypercall_pa" + " STR(__HYPERVISOR_##name * 32)  \

 49                 : "=a" (__res)                                          \

 50                 :                                                       \
 51                 : "memory" );                                           \

 52         (type)__res;                                                    \

 53 })

I have few doubts in the code. 

The name argument in the above macro referes to the name(string type) of the hypercall like: do_vcpu_op, is it correct?

What does the type argument refering to? 

Should this code be invoked from kernel-space or user-space (if CONFIG_XENFS is enabled).

--
Srujan D. Kotikela

On Tue, Jun 21, 2011 at 9:12 AM, Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx> wrote:

On Mon, 20 Jun 2011, Srujan Kotikela wrote:
> Hi,
>
> I am trying to make a hypercall from a HVM guest. I tried by copying all the xen-libs from Dom0 to DomU. I am getting an
> error PRIV_CMD not found (obviously). I have searched online and found installing PV on HVM drivers is a way to go about
> it. However, this won't guarantee that I can make all the hypercalls (correct me if I am wrong).
>
> I am trying to invoke a custom hypercall (done by modifying xen_source in dom0). So, is it not possible to have just the
> priv cmd interface in the DomU and invoke a hypercall with xen libraries copied from Dom0 (these libs have my custom
> hypercall included)?

What kernel version are you using?
If you make sure CONFIG_XEN_PVHVM is enabled in your kernel config, you
should have all the mechanisms in place in the kernel to issue
hypercalls.
At that point if you also make sure CONFIG_XENFS is enabled, you should
also be able to issue hypercalls from userland.

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