[PATCH v2 13/37] KVM: PPC: Book3S HV P9: Move radix MMU switching instructions together

[Nicholas Piggin]

Excerpts from Fabiano Rosas's message of February 27, 2021 1:56 am:
> Nicholas Piggin <npiggin at gmail.com> writes:
> 
>> Switching the MMU from radix<->radix mode is tricky particularly as the
>> MMU can remain enabled and requires a certain sequence of SPR updates.
>> Move these together into their own functions.
>>
>> This also includes the radix TLB check / flush because it's tied in to
>> MMU switching due to tlbiel getting LPID from LPIDR.
>>
>> (XXX: isync / hwsync synchronisation TBD)
> 
> I see bot mtlpidr and mtlpcr requiring a CSI in the ISA. Do you say we
> might need more than an isync?

We might need a CSI before it, we might also need a hwsync before it. I
don't know whether we need isyncs between any of them (I don't think we
should because they're all mtsprs).


> 
> Regardless, I'd expect that to be separate from the refactoring here,
> so:
> 
> Reviewed-by: Fabiano Rosas <farosas at linux.ibm.com>

Thanks,
Nick
> 
>>
>> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
>> ---
>>  arch/powerpc/kvm/book3s_hv.c | 55 +++++++++++++++++++++---------------
>>  1 file changed, 32 insertions(+), 23 deletions(-)
>>
>> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
>> index 895090636295..23d6dc04b0e9 100644
>> --- a/arch/powerpc/kvm/book3s_hv.c
>> +++ b/arch/powerpc/kvm/book3s_hv.c
>> @@ -3440,12 +3440,38 @@ static noinline void kvmppc_run_core(struct kvmppc_vcore *vc)
>>  	trace_kvmppc_run_core(vc, 1);
>>  }
>>
>> +static void switch_mmu_to_guest_radix(struct kvm *kvm, struct kvm_vcpu *vcpu, u64 lpcr)
>> +{
>> +	struct kvmppc_vcore *vc = vcpu->arch.vcore;
>> +	struct kvm_nested_guest *nested = vcpu->arch.nested;
>> +	u32 lpid;
>> +
>> +	lpid = nested ? nested->shadow_lpid : kvm->arch.lpid;
>> +
>> +	mtspr(SPRN_LPID, lpid);
>> +	mtspr(SPRN_LPCR, lpcr);
>> +	mtspr(SPRN_PID, vcpu->arch.pid);
>> +	isync();
>> +
>> +	/* TLBIEL must have LPIDR set, so set guest LPID before flushing. */
>> +	kvmppc_check_need_tlb_flush(kvm, vc->pcpu, nested);
>> +}
>> +
>> +static void switch_mmu_to_host_radix(struct kvm *kvm, u32 pid)
>> +{
>> +	mtspr(SPRN_PID, pid);
>> +	mtspr(SPRN_LPID, kvm->arch.host_lpid);
>> +	mtspr(SPRN_LPCR, kvm->arch.host_lpcr);
>> +	isync();
>> +}
>> +
>>  /*
>>   * Load up hypervisor-mode registers on P9.
>>   */
>>  static int kvmhv_load_hv_regs_and_go(struct kvm_vcpu *vcpu, u64 time_limit,
>>  				     unsigned long lpcr)
>>  {
>> +	struct kvm *kvm = vcpu->kvm;
>>  	struct kvmppc_vcore *vc = vcpu->arch.vcore;
>>  	s64 hdec;
>>  	u64 tb, purr, spurr;
>> @@ -3468,12 +3494,12 @@ static int kvmhv_load_hv_regs_and_go(struct kvm_vcpu *vcpu, u64 time_limit,
>>  	 * P8 and P9 suppress the HDEC exception when LPCR[HDICE] = 0,
>>  	 * so set HDICE before writing HDEC.
>>  	 */
>> -	mtspr(SPRN_LPCR, vcpu->kvm->arch.host_lpcr | LPCR_HDICE);
>> +	mtspr(SPRN_LPCR, kvm->arch.host_lpcr | LPCR_HDICE);
>>  	isync();
>>
>>  	hdec = time_limit - mftb();
>>  	if (hdec < 0) {
>> -		mtspr(SPRN_LPCR, vcpu->kvm->arch.host_lpcr);
>> +		mtspr(SPRN_LPCR, kvm->arch.host_lpcr);
>>  		isync();
>>  		return BOOK3S_INTERRUPT_HV_DECREMENTER;
>>  	}
>> @@ -3508,7 +3534,6 @@ static int kvmhv_load_hv_regs_and_go(struct kvm_vcpu *vcpu, u64 time_limit,
>>  	}
>>  	mtspr(SPRN_CIABR, vcpu->arch.ciabr);
>>  	mtspr(SPRN_IC, vcpu->arch.ic);
>> -	mtspr(SPRN_PID, vcpu->arch.pid);
>>
>>  	mtspr(SPRN_PSSCR, vcpu->arch.psscr | PSSCR_EC |
>>  	      (local_paca->kvm_hstate.fake_suspend << PSSCR_FAKE_SUSPEND_LG));
>> @@ -3522,8 +3547,7 @@ static int kvmhv_load_hv_regs_and_go(struct kvm_vcpu *vcpu, u64 time_limit,
>>
>>  	mtspr(SPRN_AMOR, ~0UL);
>>
>> -	mtspr(SPRN_LPCR, lpcr);
>> -	isync();
>> +	switch_mmu_to_guest_radix(kvm, vcpu, lpcr);
>>
>>  	kvmppc_xive_push_vcpu(vcpu);
>>
>> @@ -3562,7 +3586,6 @@ static int kvmhv_load_hv_regs_and_go(struct kvm_vcpu *vcpu, u64 time_limit,
>>  		mtspr(SPRN_DAWR1, host_dawr1);
>>  		mtspr(SPRN_DAWRX1, host_dawrx1);
>>  	}
>> -	mtspr(SPRN_PID, host_pidr);
>>
>>  	/*
>>  	 * Since this is radix, do a eieio; tlbsync; ptesync sequence in
>> @@ -3577,9 +3600,6 @@ static int kvmhv_load_hv_regs_and_go(struct kvm_vcpu *vcpu, u64 time_limit,
>>  	if (cpu_has_feature(CPU_FTR_ARCH_31))
>>  		asm volatile(PPC_CP_ABORT);
>>
>> -	mtspr(SPRN_LPID, vcpu->kvm->arch.host_lpid);	/* restore host LPID */
>> -	isync();
>> -
>>  	vc->dpdes = mfspr(SPRN_DPDES);
>>  	vc->vtb = mfspr(SPRN_VTB);
>>  	mtspr(SPRN_DPDES, 0);
>> @@ -3596,7 +3616,8 @@ static int kvmhv_load_hv_regs_and_go(struct kvm_vcpu *vcpu, u64 time_limit,
>>  	}
>>
>>  	mtspr(SPRN_HDEC, 0x7fffffff);
>> -	mtspr(SPRN_LPCR, vcpu->kvm->arch.host_lpcr);
>> +
>> +	switch_mmu_to_host_radix(kvm, host_pidr);
>>
>>  	return trap;
>>  }
>> @@ -4130,7 +4151,7 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit,
>>  {
>>  	struct kvm_run *run = vcpu->run;
>>  	int trap, r, pcpu;
>> -	int srcu_idx, lpid;
>> +	int srcu_idx;
>>  	struct kvmppc_vcore *vc;
>>  	struct kvm *kvm = vcpu->kvm;
>>  	struct kvm_nested_guest *nested = vcpu->arch.nested;
>> @@ -4204,13 +4225,6 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit,
>>  	vc->vcore_state = VCORE_RUNNING;
>>  	trace_kvmppc_run_core(vc, 0);
>>
>> -	if (cpu_has_feature(CPU_FTR_HVMODE)) {
>> -		lpid = nested ? nested->shadow_lpid : kvm->arch.lpid;
>> -		mtspr(SPRN_LPID, lpid);
>> -		isync();
>> -		kvmppc_check_need_tlb_flush(kvm, pcpu, nested);
>> -	}
>> -
>>  	guest_enter_irqoff();
>>
>>  	srcu_idx = srcu_read_lock(&kvm->srcu);
>> @@ -4229,11 +4243,6 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit,
>>
>>  	srcu_read_unlock(&kvm->srcu, srcu_idx);
>>
>> -	if (cpu_has_feature(CPU_FTR_HVMODE)) {
>> -		mtspr(SPRN_LPID, kvm->arch.host_lpid);
>> -		isync();
>> -	}
>> -
>>  	set_irq_happened(trap);
>>
>>  	kvmppc_set_host_core(pcpu);
>