diff options
Diffstat (limited to 'target/i386/kvm/xen-emu.c')
| -rw-r--r-- | target/i386/kvm/xen-emu.c | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/target/i386/kvm/xen-emu.c b/target/i386/kvm/xen-emu.c index b52617df54..9e22c9fa02 100644 --- a/target/i386/kvm/xen-emu.c +++ b/target/i386/kvm/xen-emu.c @@ -131,6 +131,38 @@ int kvm_xen_init(KVMState *s, uint32_t hypercall_msr) return ret; } + /* If called a second time, don't repeat the rest of the setup. */ + if (s->xen_caps) { + return 0; + } + + /* + * Event channel delivery via GSI/PCI_INTX needs to poll the vcpu_info + * of vCPU0 to deassert the IRQ when ->evtchn_upcall_pending is cleared. + * + * In the kernel, there's a notifier hook on the PIC/IOAPIC which allows + * such things to be polled at precisely the right time. We *could* do + * it nicely in the kernel: check vcpu_info[0]->evtchn_upcall_pending at + * the moment the IRQ is acked, and see if it should be reasserted. + * + * But the in-kernel irqchip is deprecated, so we're unlikely to add + * that support in the kernel. Insist on using the split irqchip mode + * instead. + * + * This leaves us polling for the level going low in QEMU, which lacks + * the appropriate hooks in its PIC/IOAPIC code. Even VFIO is sending a + * spurious 'ack' to an INTX IRQ every time there's any MMIO access to + * the device (for which it has to unmap the device and trap access, for + * some period after an IRQ!!). In the Xen case, we do it on exit from + * KVM_RUN, if the flag is set to say that the GSI is currently asserted. + * Which is kind of icky, but less so than the VFIO one. I may fix them + * both later... + */ + if (!kvm_kernel_irqchip_split()) { + error_report("kvm: Xen support requires kernel-irqchip=split"); + return -EINVAL; + } + s->xen_caps = xen_caps; return 0; } @@ -684,7 +716,9 @@ static bool handle_set_param(struct kvm_xen_exit *exit, X86CPU *cpu, switch (hp.index) { case HVM_PARAM_CALLBACK_IRQ: + qemu_mutex_lock_iothread(); err = xen_evtchn_set_callback_param(hp.value); + qemu_mutex_unlock_iothread(); xen_set_long_mode(exit->u.hcall.longmode); break; default: |