• Michael S. Tsirkin's avatar
    KVM: host side for eoi optimization · ae7a2a3f
    Michael S. Tsirkin authored
    Implementation of PV EOI using shared memory.
    This reduces the number of exits an interrupt
    causes as much as by half.
    
    The idea is simple: there's a bit, per APIC, in guest memory,
    that tells the guest that it does not need EOI.
    We set it before injecting an interrupt and clear
    before injecting a nested one. Guest tests it using
    a test and clear operation - this is necessary
    so that host can detect interrupt nesting -
    and if set, it can skip the EOI MSR.
    
    There's a new MSR to set the address of said register
    in guest memory. Otherwise not much changed:
    - Guest EOI is not required
    - Register is tested & ISR is automatically cleared on exit
    
    For testing results see description of previous patch
    'kvm_para: guest side for eoi avoidance'.
    Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
    Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
    ae7a2a3f
cpuid.c 17.3 KB