On 12/14/20 8:39 AM, David Woodhouse wrote:
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index df44d9e50adc..e627139cf8cd 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -8896,7 +8896,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
> kvm_x86_ops.msr_filter_changed(vcpu);
> }
>
> - if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) {
> + if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win ||
> + kvm_xen_has_interrupt(vcpu)) {
> ++vcpu->stat.req_event;
> kvm_apic_accept_events(vcpu);
> if (vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED) {
> diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
> index 17cbb4462b7e..4bc9da9fcfb8 100644
> --- a/arch/x86/kvm/xen.c
> +++ b/arch/x86/kvm/xen.c
> @@ -176,6 +176,45 @@ void kvm_xen_setup_runstate_page(struct kvm_vcpu *v)
> kvm_xen_update_runstate(v, RUNSTATE_running, steal_time);
> }
>
> +int kvm_xen_has_interrupt(struct kvm_vcpu *v)
> +{
> + u8 rc = 0;
> +
> + /*
> + * If the global upcall vector (HVMIRQ_callback_vector) is set and
> + * the vCPU's evtchn_upcall_pending flag is set, the IRQ is pending.
> + */
> + if (v->arch.xen.vcpu_info_set && v->kvm->arch.xen.upcall_vector) {
> + struct gfn_to_hva_cache *ghc = &v->arch.xen.vcpu_info_cache;
> + struct kvm_memslots *slots = kvm_memslots(v->kvm);
> + unsigned int offset = offsetof(struct vcpu_info, evtchn_upcall_pending);
> +
To have less nesting, wouldn't it be better to invert the logic?
say:
u8 rc = 0;
struct gfn_to_hva_cache *ghc
struct kvm_memslots *slots;
unsigned int offset;
if (!v->arch.xen.vcpu_info_set || !v->kvm->arch.xen.upcall_vector)
return 0;
BUILD_BUG_ON(...)
ghc = &v->arch.xen.vcpu_info_cache;
slots = kvm_memslots(v->kvm);
offset = offsetof(struct vcpu_info, evtchn_upcall_pending);
But I think there's a flaw here. That is handling the case where you don't have a
vcpu_info registered, and only shared info. The vcpu_info is then placed elsewhere, i.e.
another offset out of shared_info -- which is *I think* the case for PVHVM Windows guests.
Perhaps introducing a helper which adds xen_vcpu_info() and returns you the hva (picking
the right cache) similar to the RFC patch. Albeit that was with page pinning, but
borrowing an older version I had with hva_to_gfn_cache incantation would probably look like:
if (v->arch.xen.vcpu_info_set) {
ghc = &v->arch.xen.vcpu_info_cache;
} else {
ghc = &v->arch.xen.vcpu_info_cache;
offset += offsetof(struct shared_info, vcpu_info);
offset += (v - kvm_get_vcpu_by_id(0)) * sizeof(struct vcpu_info);
}
if (likely(slots->generation == ghc->generation &&
!kvm_is_error_hva(ghc->hva) && ghc->memslot)) {
/* Fast path */
__get_user(rc, (u8 __user *)ghc->hva + offset);
} else {
/* Slow path */
kvm_read_guest_offset_cached(v->kvm, ghc, &rc, offset,
sizeof(rc));
}
?
Joao
