[PATCH v2 2/5] KVM: ARM: on IO mem abort - route the call to KVM MMIO bus

[Nikolay Nikolaev]

On Mon, Jan 12, 2015 at 7:09 PM, Eric Auger <eric.auger at linaro.org> wrote:
> Hi Nikolay,
> On 12/07/2014 10:37 AM, Nikolay Nikolaev wrote:
>> On IO memory abort, try to handle the MMIO access thorugh the KVM
>> registered read/write callbacks. This is done by invoking the relevant
>> kvm_io_bus_* API.
>>
>> Signed-off-by: Nikolay Nikolaev <n.nikolaev at virtualopensystems.com>
>> ---
>>  arch/arm/kvm/mmio.c |   33 +++++++++++++++++++++++++++++++++
>>  1 file changed, 33 insertions(+)
>>
>> diff --git a/arch/arm/kvm/mmio.c b/arch/arm/kvm/mmio.c
>> index 4cb5a93..e42469f 100644
>> --- a/arch/arm/kvm/mmio.c
>> +++ b/arch/arm/kvm/mmio.c
>> @@ -162,6 +162,36 @@ static int decode_hsr(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>>       return 0;
>>  }
>>
>> +/**
>> + * handle_kernel_mmio - handle an in-kernel MMIO access
>> + * @vcpu:    pointer to the vcpu performing the access
>> + * @run:     pointer to the kvm_run structure
>> + * @mmio:    pointer to the data describing the access
>> + *
>> + * returns true if the MMIO access has been performed in kernel space,
>> + * and false if it needs to be emulated in user space.
>> + */
>> +static bool handle_kernel_mmio(struct kvm_vcpu *vcpu, struct kvm_run *run,
>> +             struct kvm_exit_mmio *mmio)
>> +{
>> +     int ret;
>> +
>> +     if (mmio->is_write) {
>> +             ret = kvm_io_bus_write(vcpu, KVM_MMIO_BUS, mmio->phys_addr,
>> +                             mmio->len, &mmio->data);
>> +
>> +     } else {
>> +             ret = kvm_io_bus_read(vcpu, KVM_MMIO_BUS, mmio->phys_addr,
>> +                             mmio->len, &mmio->data);
>> +     }
>> +     if (!ret) {
>> +             kvm_prepare_mmio(run, mmio);
>> +             kvm_handle_mmio_return(vcpu, run);
>> +     }
>> +
>> +     return !ret;
> in case ret < 0 (-EOPNOTSUPP = -95) aren't we returning true too? return
> (ret==0)?
>
>> +}
>> +
>>  int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
>>                phys_addr_t fault_ipa)
>>  {
>> @@ -200,6 +230,9 @@ int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
>>       if (vgic_handle_mmio(vcpu, run, &mmio))
>>               return 1;
>>
>> +     if (handle_kernel_mmio(vcpu, run, &mmio))
>> +             return 1;
>> +
>>       kvm_prepare_mmio(run, &mmio);
>>       return 0;
> currently the io_mem_abort returned value is not used by mmu.c code. I
> think this should be handed in kvm_handle_guest_abort. What do you think?

You're right that the returned value is not handled further after we
exit io_mem_abort, it's just passed up the call stack.
However I'm not sure how to handle it better. If you have ideas, please share.

regards,
Nikolay Nikolaev

>
> Best Regards
>
> Eric
>>  }
>>
>