Excerpts from Paul Mackerras's message of March 31, 2021 2:34 pm:
> On Tue, Mar 23, 2021 at 11:02:23AM +1000, Nicholas Piggin wrote:
>> This bit only applies to hash partitions.
>>
>> Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
>> ---
>> arch/powerpc/kvm/book3s_hv.c | 6 ++++++
>> arch/powerpc/kvm/book3s_hv_nested.c | 3 +--
>> 2 files changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
>> index c5de7e3f22b6..1ffb0902e779 100644
>> --- a/arch/powerpc/kvm/book3s_hv.c
>> +++ b/arch/powerpc/kvm/book3s_hv.c
>> @@ -1645,6 +1645,12 @@ static int kvm_arch_vcpu_ioctl_set_sregs_hv(struct kvm_vcpu *vcpu,
>> */
>> unsigned long kvmppc_filter_lpcr_hv(struct kvmppc_vcore *vc, unsigned long lpcr)
>> {
>> + struct kvm *kvm = vc->kvm;
>> +
>> + /* LPCR_TC only applies to HPT guests */
>> + if (kvm_is_radix(kvm))
>> + lpcr &= ~LPCR_TC;
>
> I'm not sure I see any benefit from this, and it is a little extra
> complexity.
Principle of allowing a guest to mess with as little HV state as
possible (but not littler), which I think is a good one to follow.
>
>> /* On POWER8 and above, userspace can modify AIL */
>> if (!cpu_has_feature(CPU_FTR_ARCH_207S))
>> lpcr &= ~LPCR_AIL;
>> diff --git a/arch/powerpc/kvm/book3s_hv_nested.c b/arch/powerpc/kvm/book3s_hv_nested.c
>> index f7b441b3eb17..851e3f527eb2 100644
>> --- a/arch/powerpc/kvm/book3s_hv_nested.c
>> +++ b/arch/powerpc/kvm/book3s_hv_nested.c
>> @@ -140,8 +140,7 @@ static void sanitise_hv_regs(struct kvm_vcpu *vcpu, struct hv_guest_state *hr)
>> /*
>> * Don't let L1 change LPCR bits for the L2 except these:
>> */
>> - mask = LPCR_DPFD | LPCR_ILE | LPCR_TC | LPCR_AIL | LPCR_LD |
>> - LPCR_LPES | LPCR_MER;
>> + mask = LPCR_DPFD | LPCR_ILE | LPCR_AIL | LPCR_LD | LPCR_LPES | LPCR_MER;
>
> Doesn't this make it completely impossible to set TC for any guest?
Argh, yes Fabiano pointed this out in an earlier rev and I didn't
fix this hunk after adding the filter bit. Thanks.
Thanks,
Nick
