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Re: [Xen-devel] PRIVCMD in HVM DomU

To: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] PRIVCMD in HVM DomU
From: Srujan Kotikela <ksrujandas@xxxxxxxxx>
Date: Tue, 21 Jun 2011 10:53:15 -0500
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I am using 2.6.18 kernel. I am going to try with a newer kernel (>=

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
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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