Re: [Xen-devel] [V10 PATCH 21/23] PVH xen: VMX support of PVH guest creation/destruction

[George Dunlap <dunlapg@xxxxxxxxx>]

On Wed, Jul 24, 2013 at 2:59 AM, Mukesh Rathor <mukesh.rathor@xxxxxxxxxx> wrote:
> This patch implements the vmx portion of the guest create, ie
> vcpu and domain initialization. Some changes to support the destroy path.
>
> Change in V10:
>   - Don't call vmx_domain_initialise / vmx_domain_destroy for PVH.
>   - Do not set hvm_vcpu.guest_efer here in vmx.c.
>
> Signed-off-by: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>
> ---
>  xen/arch/x86/hvm/vmx/vmx.c |   28 ++++++++++++++++++++++++++++
>  1 files changed, 28 insertions(+), 0 deletions(-)
>
> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> index 80109c1..f6ea39a 100644
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -1076,6 +1076,28 @@ static void vmx_update_host_cr3(struct vcpu *v)
>      vmx_vmcs_exit(v);
>  }
>
> +/*
> + * PVH guest never causes CR3 write vmexit. This is called during the guest
> + * setup.
> + */
> +static void vmx_update_pvh_cr(struct vcpu *v, unsigned int cr)
> +{
> +    vmx_vmcs_enter(v);
> +    switch ( cr )
> +    {
> +    case 3:
> +        __vmwrite(GUEST_CR3, v->arch.hvm_vcpu.guest_cr[3]);
> +        hvm_asid_flush_vcpu(v);
> +        break;
> +
> +    default:
> +        printk(XENLOG_ERR
> +               "PVH: d%d v%d unexpected cr%d update at rip:%lx\n",
> +               v->domain->domain_id, v->vcpu_id, cr, __vmread(GUEST_RIP));
> +    }
> +    vmx_vmcs_exit(v);
> +}

This function seems almost completely pointless.  In the case of CR3,
it basically does exactly what the function below does.  It avoids
maybe doing something pointless, like vmx_load_ptrs(), but that should
be harmless, right?

This patch could be taken out entirely, or replaced with a simple
if(is_pvh_vcpu(v)) ASSERT(cr == 3);

 -George

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