Re: [PATCH 8/8] KVM: xen: automatically use the vcpu_info embedded in shared_info

[Paul Durrant]

On 14/09/2023 10:09, David Woodhouse wrote:
> On Thu, 2023-09-14 at 08:49 +0000, Paul Durrant wrote:
> > From: Paul Durrant <pdurrant@xxxxxxxxxx>
> >
> > Add a KVM_XEN_HVM_CONFIG_DEFAULT_VCPU_INFO flag so that the VMM knows it
> > need only set the KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO attribute in response to
> > a VCPUOP_register_vcpu_info hypercall, and modify get_vcpu_info_cache()
> > to pass back a pointer to the shared info pfn cache (and appropriate
> > offset) for any of the first 32 vCPUs if the attribute has not been set.
>
> Might be simpler just to link this behaviour to the
> KVM_XEN_ATTR_TYPE_SHARED_INFO_HVA support? If userspace sets the
> shared_info as an HVA, then the default vcpu_info will be used therein.

Well there's no problem in using the default embedded vcpu_info even if 
the guests sets the shared_info via GPA... it still saves the VMM making 
a few ioctls. So do we really want to link the two things?

  Paul