On Wed, Jul 19, 2023 at 05:54:00PM +0000, Raghavendra Rao Ananta wrote: > For protected kvm, the CPU hotplug 'down' logic currently brings > down the timer and vGIC, essentially disabling interrupts. However, > because of how the 'kvm_arm_hardware_enabled' flag is designed, it > never re-enables them back on the CPU hotplug 'up' path. Hence, > clean up the logic to maintain the CPU hotplug up/down symmetry. Correct me if I am wrong, but this issue exists outside of cpu hotplug, right? init_subsystems() calls _kvm_arch_hardware_enable() on all cores, which only sets up the hyp cpu context and not the percpu interrupts. Similar issue exists for the cpu that calls do_pkvm_init(). I'll also note kvm_arm_hardware_enabled is deceptively vague, as it only keeps track of whether or not the hyp cpu context has been initialized. May send a cleanup here in a bit. Perhaps this for the changelog: KVM: arm64: Fix hardware enable/disable flows for pKVM When running in protected mode, the hyp stub is disabled after pKVM is initialized, meaning the host cannot enable/disable the hyp at runtime. As such, kvm_arm_hardware_enabled is always 1 after initialization, and kvm_arch_hardware_enable() never enables the vgic maintenance irq or timer irqs. Unconditionally enable/disable the vgic + timer irqs in the respective calls, instead relying on the percpu bookkeeping in the generic code to keep track of which cpus have the interrupts unmasked. > Fixes: 466d27e48d7c ("KVM: arm64: Simplify the CPUHP logic") > Reported-by: Oliver Upton <oliver.upton@xxxxxxxxx> > Suggested-by: Oliver Upton <oliver.upton@xxxxxxxxx> > Signed-off-by: Raghavendra Rao Ananta <rananta@xxxxxxxxxx> > --- > arch/arm64/kvm/arm.c | 14 ++++---------- > 1 file changed, 4 insertions(+), 10 deletions(-) > > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c > index c2c14059f6a8..010ebfa69650 100644 > --- a/arch/arm64/kvm/arm.c > +++ b/arch/arm64/kvm/arm.c > @@ -1867,14 +1867,10 @@ static void _kvm_arch_hardware_enable(void *discard) > > int kvm_arch_hardware_enable(void) > { > - int was_enabled = __this_cpu_read(kvm_arm_hardware_enabled); > - > _kvm_arch_hardware_enable(NULL); > > - if (!was_enabled) { > - kvm_vgic_cpu_up(); > - kvm_timer_cpu_up(); > - } > + kvm_vgic_cpu_up(); > + kvm_timer_cpu_up(); > > return 0; > } > @@ -1889,10 +1885,8 @@ static void _kvm_arch_hardware_disable(void *discard) > > void kvm_arch_hardware_disable(void) > { > - if (__this_cpu_read(kvm_arm_hardware_enabled)) { > - kvm_timer_cpu_down(); > - kvm_vgic_cpu_down(); > - } > + kvm_timer_cpu_down(); > + kvm_vgic_cpu_down(); > > if (!is_protected_kvm_enabled()) > _kvm_arch_hardware_disable(NULL); > -- > 2.41.0.487.g6d72f3e995-goog > -- Thanks, Oliver