| Message ID | 20210305150638.2675513-4-npiggin@gmail.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | KVM: PPC: Book3S: C-ify the P9 entry/exit code | expand |
| Related | show |
Hi Nick, > This SPR is set to 0 twice when exiting the guest. > Indeed it is. I checked the ISA because I'd never heard of the PSPB SPR before! It's the Problem State Priority Boost register. Before I knew what it was, I was slightly concerned that the chip might change the value while the other mtsprs were running, but given that it's just affects the priority boost states that problem state can use, I don't think that is actually going to happen. I also checked the commit that introduced it - commit 95a6432ce903 ("KVM: PPC: Book3S HV: Streamlined guest entry/exit path on P9 for radix guests"), and there wasn't any justification for having a double mtspr. So, this seems good: Reviewed-by: Daniel Axtens <dja@axtens.net> Kind regards, Daniel > Suggested-by: Fabiano Rosas <farosas@linux.ibm.com> > Signed-off-by: Nicholas Piggin <npiggin@gmail.com> > --- > arch/powerpc/kvm/book3s_hv.c | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c > index 2e29b96ef775..0542d7f17dc3 100644 > --- a/arch/powerpc/kvm/book3s_hv.c > +++ b/arch/powerpc/kvm/book3s_hv.c > @@ -3758,7 +3758,6 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit, > mtspr(SPRN_DSCR, host_dscr); > mtspr(SPRN_TIDR, host_tidr); > mtspr(SPRN_IAMR, host_iamr); > - mtspr(SPRN_PSPB, 0); > > if (host_amr != vcpu->arch.amr) > mtspr(SPRN_AMR, host_amr); > -- > 2.23.0
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index 2e29b96ef775..0542d7f17dc3 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -3758,7 +3758,6 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit, mtspr(SPRN_DSCR, host_dscr); mtspr(SPRN_TIDR, host_tidr); mtspr(SPRN_IAMR, host_iamr); - mtspr(SPRN_PSPB, 0); if (host_amr != vcpu->arch.amr) mtspr(SPRN_AMR, host_amr);
This SPR is set to 0 twice when exiting the guest. Suggested-by: Fabiano Rosas <farosas@linux.ibm.com> Signed-off-by: Nicholas Piggin <npiggin@gmail.com> --- arch/powerpc/kvm/book3s_hv.c | 1 - 1 file changed, 1 deletion(-)