• Radim Krčmář's avatar
    KVM: x86: add KVM_CAP_X2APIC_API · 37131313
    Radim Krčmář authored
    KVM_CAP_X2APIC_API is a capability for features related to x2APIC
    enablement.  KVM_X2APIC_API_32BIT_FORMAT feature can be enabled to
    extend APIC ID in get/set ioctl and MSI addresses to 32 bits.
    Both are needed to support x2APIC.
    
    The feature has to be enableable and disabled by default, because
    get/set ioctl shifted and truncated APIC ID to 8 bits by using a
    non-standard protocol inspired by xAPIC and the change is not
    backward-compatible.
    
    Changes to MSI addresses follow the format used by interrupt remapping
    unit.  The upper address word, that used to be 0, contains upper 24 bits
    of the LAPIC address in its upper 24 bits.  Lower 8 bits are reserved as
    0.  Using the upper address word is not backward-compatible either as we
    didn't check that userspace zeroed the word.  Reserved bits are still
    not explicitly checked, but non-zero data will affect LAPIC addresses,
    which will cause a bug.
    Signed-off-by: default avatarRadim Krčmář <rkrcmar@redhat.com>
    Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
    37131313
irq_comm.c 11.5 KB