Re: [RFC PATCH 06/17] KVM: PPC: e500: Add emulation helper for getting instruction ea

[Alexander Graf <agraf@suse.de>]

On 05.07.2012, at 13:39, Caraman Mihai Claudiu-B02008 wrote:

>> -----Original Message-----
>> From: kvm-ppc-owner@vger.kernel.org [mailto:kvm-ppc-
>> owner@vger.kernel.org] On Behalf Of Alexander Graf
>> Sent: Wednesday, July 04, 2012 4:56 PM
>> To: Caraman Mihai Claudiu-B02008
>> Cc: kvm-ppc@vger.kernel.org; kvm@vger.kernel.org; linuxppc-
>> dev@lists.ozlabs.org; qemu-ppc@nongnu.org
>> Subject: Re: [RFC PATCH 06/17] KVM: PPC: e500: Add emulation helper for
>> getting instruction ea
>> 
>> 
>> On 25.06.2012, at 14:26, Mihai Caraman wrote:
>> 
>>> Add emulation helper for getting instruction ea and refactor tlb
>> instruction
>>> emulation to use it.
>>> 
>>> Signed-off-by: Mihai Caraman <mihai.caraman@freescale.com>
>>> ---
>>> arch/powerpc/kvm/e500.h         |    6 +++---
>>> arch/powerpc/kvm/e500_emulate.c |   21 ++++++++++++++++++---
>>> arch/powerpc/kvm/e500_tlb.c     |   23 ++++++-----------------
>>> 3 files changed, 27 insertions(+), 23 deletions(-)
>>> 
>>> diff --git a/arch/powerpc/kvm/e500.h b/arch/powerpc/kvm/e500.h
>>> index 3e31098..70bfed4 100644
>>> --- a/arch/powerpc/kvm/e500.h
>>> +++ b/arch/powerpc/kvm/e500.h
>>> @@ -130,9 +130,9 @@ int kvmppc_e500_emul_mt_mmucsr0(struct
>> kvmppc_vcpu_e500 *vcpu_e500,
>>> 				ulong value);
>>> int kvmppc_e500_emul_tlbwe(struct kvm_vcpu *vcpu);
>>> int kvmppc_e500_emul_tlbre(struct kvm_vcpu *vcpu);
>>> -int kvmppc_e500_emul_tlbivax(struct kvm_vcpu *vcpu, int ra, int rb);
>>> -int kvmppc_e500_emul_tlbilx(struct kvm_vcpu *vcpu, int rt, int ra, int
>> rb);
>>> -int kvmppc_e500_emul_tlbsx(struct kvm_vcpu *vcpu, int rb);
>>> +int kvmppc_e500_emul_tlbivax(struct kvm_vcpu *vcpu, gva_t ea);
>>> +int kvmppc_e500_emul_tlbilx(struct kvm_vcpu *vcpu, int rt, gva_t ea);
>>> +int kvmppc_e500_emul_tlbsx(struct kvm_vcpu *vcpu, gva_t ea);
>>> int kvmppc_e500_tlb_init(struct kvmppc_vcpu_e500 *vcpu_e500);
>>> void kvmppc_e500_tlb_uninit(struct kvmppc_vcpu_e500 *vcpu_e500);
>>> 
>>> diff --git a/arch/powerpc/kvm/e500_emulate.c
>> b/arch/powerpc/kvm/e500_emulate.c
>>> index 8b99e07..81288f7 100644
>>> --- a/arch/powerpc/kvm/e500_emulate.c
>>> +++ b/arch/powerpc/kvm/e500_emulate.c
>>> @@ -82,6 +82,17 @@ static int kvmppc_e500_emul_msgsnd(struct kvm_vcpu
>> *vcpu, int rb)
>>> }
>>> #endif
>>> 
>>> +static inline ulong kvmppc_get_ea_indexed(struct kvm_vcpu *vcpu, int
>> ra, int rb)
>>> +{
>>> +	ulong ea;
>>> +
>>> +	ea = kvmppc_get_gpr(vcpu, rb);
>>> +	if (ra)
>>> +		ea += kvmppc_get_gpr(vcpu, ra);
>>> +
>>> +	return ea;
>>> +}
>>> +
>> 
>> Please move this one to arch/powerpc/include/asm/kvm_ppc.h.
> 
> Yep. This is similar with what I had in my internal version before emulation
> refactoring took place upstream. The only difference is that I split the embedded
> and server implementation touching this files:
> 	arch/powerpc/include/asm/kvm_booke.h
> 	arch/powerpc/include/asm/kvm_book3s.h
> 
> Which approach do you prefer?

This is generic code to me, so it shouldn't go into booke/book3s specific files.

> 
>> 
>>> int kvmppc_core_emulate_op(struct kvm_run *run, struct kvm_vcpu *vcpu,
>>>                           unsigned int inst, int *advance)
>>> {
>>> @@ -89,6 +100,7 @@ int kvmppc_core_emulate_op(struct kvm_run *run,
>> struct kvm_vcpu *vcpu,
>>> 	int ra = get_ra(inst);
>>> 	int rb = get_rb(inst);
>>> 	int rt = get_rt(inst);
>>> +	gva_t ea;
>>> 
>>> 	switch (get_op(inst)) {
>>> 	case 31:
>>> @@ -113,15 +125,18 @@ int kvmppc_core_emulate_op(struct kvm_run *run,
>> struct kvm_vcpu *vcpu,
>>> 			break;
>>> 
>>> 		case XOP_TLBSX:
>>> -			emulated = kvmppc_e500_emul_tlbsx(vcpu,rb);
>>> +			ea = kvmppc_get_ea_indexed(vcpu, ra, rb);
>>> +			emulated = kvmppc_e500_emul_tlbsx(vcpu, ea);
>>> 			break;
>>> 
>>> 		case XOP_TLBILX:
>>> -			emulated = kvmppc_e500_emul_tlbilx(vcpu, rt, ra, rb);
>>> +			ea = kvmppc_get_ea_indexed(vcpu, ra, rb);
>>> +			emulated = kvmppc_e500_emul_tlbilx(vcpu, rt, ea);
>> 
>> What's the point in hiding ra+rb, but not rt? I like the idea of hiding
>> the register semantics, but please move rt into a local variable that
>> gets passed as pointer to kvmppc_e500_emul_tlbilx.
> 
> Why to send it as a pointer? rt which should be rather named t in this case
> is an [in] value for tlbilx, according to section 6.11.4.9 in the PowerISA 2.06b.

Because usually rt in the PPC ISA denotes a _t_arget _r_egister. The field here really is called "T" to denote the _t_ype of the operation which you correctly pointed out. Could you please change this misnaming along the way and mask it accordingly?


Alex