i386/kvm: Set Xen vCPU ID in KVM
There are (at least) three different vCPU ID number spaces. One is the internal KVM vCPU index, based purely on which vCPU was chronologically created in the kernel first. If userspace threads are all spawned and create their KVM vCPUs in essentially random order, then the KVM indices are basically random too. The second number space is the APIC ID space, which is consistent and useful for referencing vCPUs. MSIs will specify the target vCPU using the APIC ID, for example, and the KVM Xen APIs also take an APIC ID from userspace whenever a vCPU needs to be specified (as opposed to just using the appropriate vCPU fd). The third number space is not normally relevant to the kernel, and is the ACPI/MADT/Xen CPU number which corresponds to cs->cpu_index. But Xen timer hypercalls use it, and Xen timer hypercalls *really* want to be accelerated in the kernel rather than handled in userspace, so the kernel needs to be told. Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Reviewed-by: Paul Durrant <paul@xen.org>
This commit is contained in:
parent
f66b8a83c5
commit
5e691a955a
|
@ -1884,6 +1884,11 @@ int kvm_arch_init_vcpu(CPUState *cs)
|
|||
}
|
||||
}
|
||||
|
||||
r = kvm_xen_init_vcpu(cs);
|
||||
if (r) {
|
||||
return r;
|
||||
}
|
||||
|
||||
kvm_base += 0x100;
|
||||
#else /* CONFIG_XEN_EMU */
|
||||
/* This should never happen as kvm_arch_init() would have died first. */
|
||||
|
|
|
@ -52,6 +52,34 @@ int kvm_xen_init(KVMState *s, uint32_t hypercall_msr)
|
|||
return 0;
|
||||
}
|
||||
|
||||
int kvm_xen_init_vcpu(CPUState *cs)
|
||||
{
|
||||
int err;
|
||||
|
||||
/*
|
||||
* The kernel needs to know the Xen/ACPI vCPU ID because that's
|
||||
* what the guest uses in hypercalls such as timers. It doesn't
|
||||
* match the APIC ID which is generally used for talking to the
|
||||
* kernel about vCPUs. And if vCPU threads race with creating
|
||||
* their KVM vCPUs out of order, it doesn't necessarily match
|
||||
* with the kernel's internal vCPU indices either.
|
||||
*/
|
||||
if (kvm_xen_has_cap(EVTCHN_SEND)) {
|
||||
struct kvm_xen_vcpu_attr va = {
|
||||
.type = KVM_XEN_VCPU_ATTR_TYPE_VCPU_ID,
|
||||
.u.vcpu_id = cs->cpu_index,
|
||||
};
|
||||
err = kvm_vcpu_ioctl(cs, KVM_XEN_VCPU_SET_ATTR, &va);
|
||||
if (err) {
|
||||
error_report("kvm: Failed to set Xen vCPU ID attribute: %s",
|
||||
strerror(-err));
|
||||
return err;
|
||||
}
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
uint32_t kvm_xen_get_caps(void)
|
||||
{
|
||||
return kvm_state->xen_caps;
|
||||
|
|
|
@ -24,5 +24,6 @@
|
|||
#define XEN_VERSION(maj, min) ((maj) << 16 | (min))
|
||||
|
||||
int kvm_xen_init(KVMState *s, uint32_t hypercall_msr);
|
||||
int kvm_xen_init_vcpu(CPUState *cs);
|
||||
|
||||
#endif /* QEMU_I386_KVM_XEN_EMU_H */
|
||||
|
|
Loading…
Reference in New Issue