Excerpts from Fabiano Rosas's message of July 1, 2021 3:51 am:
> Nicholas Piggin <npig...@gmail.com> writes:
>
>> Some of the DAWR SPR access is already predicated on dawr_enabled(),
>> apply this to the remainder of the accesses.
>>
>> Signed-off-by: Nicholas Piggin <npig...@gmail.com>
>> ---
>> arch/powerpc/kvm/book3s_hv_p9_entry.c | 34 ++++++++++++++++-----------
>> 1 file changed, 20 insertions(+), 14 deletions(-)
>>
>> diff --git a/arch/powerpc/kvm/book3s_hv_p9_entry.c
>> b/arch/powerpc/kvm/book3s_hv_p9_entry.c
>> index 7aa72efcac6c..f305d1d6445c 100644
>> --- a/arch/powerpc/kvm/book3s_hv_p9_entry.c
>> +++ b/arch/powerpc/kvm/book3s_hv_p9_entry.c
>> @@ -638,13 +638,16 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64
>> time_limit, unsigned long lpc
>>
>> host_hfscr = mfspr(SPRN_HFSCR);
>> host_ciabr = mfspr(SPRN_CIABR);
>> - host_dawr0 = mfspr(SPRN_DAWR0);
>> - host_dawrx0 = mfspr(SPRN_DAWRX0);
>> host_psscr = mfspr(SPRN_PSSCR);
>> host_pidr = mfspr(SPRN_PID);
>> - if (cpu_has_feature(CPU_FTR_DAWR1)) {
>> - host_dawr1 = mfspr(SPRN_DAWR1);
>> - host_dawrx1 = mfspr(SPRN_DAWRX1);
>> +
>> + if (dawr_enabled()) {
>> + host_dawr0 = mfspr(SPRN_DAWR0);
>> + host_dawrx0 = mfspr(SPRN_DAWRX0);
>> + if (cpu_has_feature(CPU_FTR_DAWR1)) {
>> + host_dawr1 = mfspr(SPRN_DAWR1);
>> + host_dawrx1 = mfspr(SPRN_DAWRX1);
>
> The userspace needs to enable DAWR1 via KVM_CAP_PPC_DAWR1. That cap is
> not even implemented in QEMU currently, so we never allow the guest to
> set vcpu->arch.dawr1. If we check for kvm->arch.dawr1_enabled instead of
> the CPU feature, we could shave some more time here.
Ah good point, yes let's do that.
Thanks,
Nick
