Hi Amit, On 25/02/2019 17:39, James Morse wrote: > On 19/02/2019 09:24, Amit Daniel Kachhap wrote: >> From: Mark Rutland <mark.rutland@xxxxxxx> >> When restoring HCR_EL2 for the host, KVM uses HCR_HOST_VHE_FLAGS, which >> is a constant value. This works today, as the host HCR_EL2 value is >> always the same, but this will get in the way of supporting extensions >> that require HCR_EL2 bits to be set conditionally for the host. >> >> To allow such features to work without KVM having to explicitly handle >> every possible host feature combination, this patch has KVM save/restore >> for the host HCR when switching to/from a guest HCR. The saving of the >> register is done once during cpu hypervisor initialization state and is >> just restored after switch from guest. >> >> For fetching HCR_EL2 during kvm initialisation, a hyp call is made using >> kvm_call_hyp and is helpful in NHVE case. >> >> For the hyp TLB maintenance code, __tlb_switch_to_host_vhe() is updated >> to toggle the TGE bit with a RMW sequence, as we already do in >> __tlb_switch_to_guest_vhe(). >> >> The value of hcr_el2 is now stored in struct kvm_cpu_context as both host >> and guest can now use this field in a common way. >> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c >> index 9e350fd3..8e18f7f 100644 >> --- a/virt/kvm/arm/arm.c >> +++ b/virt/kvm/arm/arm.c >> @@ -1328,6 +1328,7 @@ static void cpu_hyp_reinit(void) >> cpu_init_hyp_mode(NULL); >> >> kvm_arm_init_debug(); >> + __cpu_copy_hyp_conf(); > > Your commit message says: > | The saving of the register is done once during cpu hypervisor initialization state > > But cpu_hyp_reinit() is called each time secondary CPUs come online. Its also called as > part of the cpu-idle mechanism via hyp_init_cpu_pm_notifier(). cpu-idle can ask the > firmware to power-off the CPU until an interrupt becomes pending for it. KVM's EL2 state > disappears when this happens, these calls take care of setting it back up again. On Juno, > this can happen tens of times a second, and this adds an extra call to EL2. The bit I missed was the MDCR_EL2 copy is behind kvm_arm_init_debug(), so we already have an unnecessary EL2 call here, so its nothing new. Assuming the deactivate_traps_vhe_put() vcpu isn't needed, and with Mark's comments addressed: Reviewed-by: James Morse <james.morse@xxxxxxx> If we can avoid repeated calls to EL2 once we've got HCR_EL2+MDCR_EL2, even better! Thanks, James _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
