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

[Nikolay Nikolaev]

On Sat, Nov 29, 2014 at 1:28 PM, Christoffer Dall
<christoffer.dall at linaro.org> wrote:
> On Mon, Nov 24, 2014 at 11:26:51PM +0200, 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..81230da 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;
>>  }
>>
>> +/**
>> + * kvm_handle_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;
>> +}
>> +
>>  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;
>> +
>
> Is this stuff always synchronously handled so that the mmio is properly
> populated upon handle_kernel_mmio on reads?

If I get it right the kvm_io_bus_ API is intended to work
synchronously. Of course it probably depends
on how the registered device handles the read/write call.
Or maybe I misunderstand your question? Please clarify in that case.

regards,
Nikolay Nikolaev

>
> -Christoffer