Re: [PATCH 20/30] nVMX: Exiting from L2 to L1

[Avi Kivity <avi@redhat.com>]

On 05/08/2011 11:25 AM, Nadav Har'El wrote:
> This patch implements nested_vmx_vmexit(), called when the nested L2 guest
> exits and we want to run its L1 parent and let it handle this exit.
>
> Note that this will not necessarily be called on every L2 exit. L0 may decide
> to handle a particular exit on its own, without L1's involvement; In that
> case, L0 will handle the exit, and resume running L2, without running L1 and
> without calling nested_vmx_vmexit(). The logic for deciding whether to handle
> a particular exit in L1 or in L0, i.e., whether to call nested_vmx_vmexit(),
> will appear in the next patch.
>
>
> /*
> + * prepare_vmcs12 is part of what we need to do when the nested L2 guest exits
> + * and we want to prepare to run its L1 parent. L1 keeps a vmcs for L2 (vmcs12),
> + * and this function updates it to reflect the changes to the guest state while
> + * L2 was running (and perhaps made some exits which were handled directly by L0
> + * without going back to L1), and to reflect the exit reason.
> + * Note that we do not have to copy here all VMCS fields, just those that
> + * could have changed by the L2 guest or the exit - i.e., the guest-state and
> + * exit-information fields only. Other fields are modified by L1 with VMWRITE,
> + * which already writes to vmcs12 directly.
> + */
> +void prepare_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
> +{
<snip>

> +	vmcs12->vmcs_link_pointer = vmcs_read64(VMCS_LINK_POINTER);

Again, this should be emulated, not assigned to the guest.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.