On 11/16/21 15:25, David Woodhouse wrote:
+ /*
+ * If the guest requires direct access to mapped L1 pages, check
+ * the caches are valid. Will raise KVM_REQ_GET_NESTED_STATE_PAGES
+ * to go and revalidate them, if necessary.
+ */
+ if (is_guest_mode(vcpu) && kvm_x86_ops.nested_ops->check_guest_maps)
+ kvm_x86_ops.nested_ops->check_guest_maps();
+
This should not be needed, should it? As long as the gfn-to-pfn
cache's vcpu field is handled properly, the request will just cause
the vCPU not to enter. It would have to take the gpc->lock around
changes to gpc->vcpu though (meaning: it's probably best to add a
function gfn_to_pfn_cache_set_vcpu).
Doing it lockless would be harder; I cannot think of any well-known
pattern that is good for this scenario.
That check_guest_maps() function can validate the caches which the L2
guest is actually using in the VMCS02, and if they need to be refreshed
then raising a req will immediately break out of vcpu_enter_guest() to
allow that to happen.
I*think* we can just use KVM_REQ_GET_NESTED_STATE_PAGES for that and
don't need to invent a new one?
Yes, maybe even do it unconditionally?
- if (kvm_check_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu)) {
+ if (kvm_check_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu) ||
kvm_check_request(KVM_REQ_GPC_INVALIDATE, vcpu))
if the gfn-to-pfn cache's vcpu field is set/reset properly across nested
VM entry and exit.
Paolo
