• Oliver Upton's avatar
    KVM: arm64: Load the stage-2 MMU context in kvm_vcpu_load_vhe() · 934bf871
    Oliver Upton authored
    To date the VHE code has aggressively reloaded the stage-2 MMU context
    on every guest entry, despite the fact that this isn't necessary. This
    was probably done for consistency with the nVHE code, which needs to
    switch in/out the stage-2 MMU context as both the host and guest run at
    EL1.
    
    Hoist __load_stage2() into kvm_vcpu_load_vhe(), thus avoiding a reload
    on every guest entry/exit. This is likely to be beneficial to systems
    with one of the speculative AT errata, as there is now one fewer context
    synchronization event on the guest entry path. Additionally, it is
    possible that implementations have hitched correctness mitigations on
    writes to VTTBR_EL2, which are now elided on guest re-entry.
    
    Note that __tlb_switch_to_guest() is deliberately left untouched as it
    can be called outside the context of a running vCPU.
    
    Link: https://lore.kernel.org/r/20231018233212.2888027-6-oliver.upton@linux.devSigned-off-by: default avatarOliver Upton <oliver.upton@linux.dev>
    934bf871
switch.c 7.41 KB