Re: [Xen-devel] xc_altp2m_set_vcpu_enable_notify fail

[Big Strong <fangtuo90@xxxxxxxxx>]

Your opinion is inspiring. During the past days, I've tried to directly call HVMOP_altp2m_vcpu_enable_notify in guest by ioctl, this time it fails for "domain is null" checking. I thought it might because the guest is not able to achieve the vcpu info of its current state. While in dom0, this is not a problem. But dom0 is unable to call  HVMOP_altp2m_vcpu_enable_notify for the guest. How can I solve this contradiction?

2016-05-12 23:17 GMT+08:00 Wei Liu <wei.liu2@xxxxxxxxxx>:

On Thu, May 12, 2016 at 09:00:12PM +0800, Big Strong wrote:
> I'm still not very clear why would do_altp2m_op change the domain to
> current domain (which is dom0 in my case) when the cmd is
> HVMOP_altp2m_vcpu_enable_notify
> <http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/arch/x86/hvm/hvm.c;hb=743289d0296268fe6bad64531a24d8053afeb062#l6198>.
> As to my case, it would prevent the dom0 to set the #ve info page for other
> domUs because the check of is_hvm_domain would fail
> <http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/arch/x86/hvm/hvm.c;hb=743289d0296268fe6bad64531a24d8053afeb062#l6204>and
> the function will returns directly.
>

Maybe the intent of that HVMOP is to get called directly by the guest
that is interested in such event?

I looks like a natural restriction to me because the vcpu needs to set
up handler for #ve AIUI. It's not likely that Dom0 can do this for
arbitrary guest.

Wei.

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