• Nicholas Piggin's avatar
    powerpc/64s: Revert setting of LPCR[LPES] on POWER9 · 8d1b48ef
    Nicholas Piggin authored
    The XIVE enablement patches included a change to set the LPES (Logical
    Partitioning Environment Selector) bit (bit # 3) in LPCR (Logical Partitioning
    Control Register) on POWER9 hosts. This bit sets external interrupts to guest
    delivery mode, which uses SRR0/1. The host's EE interrupt handler is written to
    expect HSRR0/1 (for earlier CPUs). This should be fine because XIVE is
    configured not to deliver EEs to the host (Hypervisor Virtulization Interrupt is
    used instead) so the EE handler should never be executed.
    
    However a bug in interrupt controller code, hardware, or odd configuration of a
    simulator could result in the host getting an EE incorrectly. Keeping the EE
    delivery mode matching the host EE handler prevents strange crashes due to using
    the wrong exception registers.
    
    KVM will configure the LPCR to set LPES prior to running a guest so that EEs are
    delivered to the guest using SRR0/1.
    
    Fixes: 08a1e650 ("powerpc: Fixup LPCR:PECE and HEIC setting on POWER9")
    Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
    [mpe: Massage change log to avoid referring to LPES0 which is now renamed LPES]
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    8d1b48ef
cpu_setup_power.S 4.64 KB