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| author | David Woodhouse <dwmw@amazon.co.uk> | 2020-12-09 20:08:30 +0000 |
|---|---|---|
| committer | David Woodhouse <dwmw@amazon.co.uk> | 2021-02-04 14:19:39 +0000 |
| commit | 40da8ccd724f7ca2f08550a46268bc3a91cc8869 (patch) | |
| tree | 7f9240ecbda4aa6a5b33cd2b75d408aed68df5d9 /arch/x86/kvm/x86.c | |
| parent | f2340cd9e41dc463cb1189274f3db560c1dfa1f4 (diff) | |
| download | lwn-40da8ccd724f7ca2f08550a46268bc3a91cc8869.tar.gz lwn-40da8ccd724f7ca2f08550a46268bc3a91cc8869.zip | |
KVM: x86/xen: Add event channel interrupt vector upcall
It turns out that we can't handle event channels *entirely* in userspace
by delivering them as ExtINT, because KVM is a bit picky about when it
accepts ExtINT interrupts from a legacy PIC. The in-kernel local APIC
has to have LVT0 configured in APIC_MODE_EXTINT and unmasked, which
isn't necessarily the case for Xen guests especially on secondary CPUs.
To cope with this, add kvm_xen_get_interrupt() which checks the
evtchn_pending_upcall field in the Xen vcpu_info, and delivers the Xen
upcall vector (configured by KVM_XEN_ATTR_TYPE_UPCALL_VECTOR) if it's
set regardless of LAPIC LVT0 configuration. This gives us the minimum
support we need for completely userspace-based implementation of event
channels.
This does mean that vcpu_enter_guest() needs to check for the
evtchn_pending_upcall flag being set, because it can't rely on someone
having set KVM_REQ_EVENT unless we were to add some way for userspace to
do so manually.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Diffstat (limited to 'arch/x86/kvm/x86.c')
| -rw-r--r-- | arch/x86/kvm/x86.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 0f648434796f..1cedbc3d2455 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -8987,7 +8987,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) static_call(kvm_x86_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) { |