On Wed, Oct 17, 2012 at 4:29 PM, Peter Maydell <peter.maydell@xxxxxxxxxx> wrote:
> On 14 October 2012 01:04, Christoffer Dall
> <c.dall@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>> On ARM (and possibly other architectures) some bits are specific to the
>> model being emulated for the guest and user space needs a way to tell
>> the kernel about those bits. An example is mmio device base addresses,
>> where KVM must know the base address for a given device to properly
>> emulate mmio accesses within a certain address range or directly map a
>> device with virtualiation extensions into the guest address space.
>>
>> We try to make this API slightly more generic than for our specific use,
>> but so far only the VGIC uses this feature.
>>
>> Signed-off-by: Christoffer Dall <c.dall@xxxxxxxxxxxxxxxxxxxxxx>
>> ---
>> Documentation/virtual/kvm/api.txt | 30 ++++++++++++++++++++++++++++++
>> arch/arm/include/asm/kvm.h | 13 +++++++++++++
>> arch/arm/include/asm/kvm_mmu.h | 1 +
>> arch/arm/include/asm/kvm_vgic.h | 6 ++++++
>> arch/arm/kvm/arm.c | 31 ++++++++++++++++++++++++++++++-
>> arch/arm/kvm/vgic.c | 34 +++++++++++++++++++++++++++++++---
>> include/linux/kvm.h | 8 ++++++++
>> 7 files changed, 119 insertions(+), 4 deletions(-)
>>
>> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
>> index 26e953d..30ddcac 100644
>> --- a/Documentation/virtual/kvm/api.txt
>> +++ b/Documentation/virtual/kvm/api.txt
>> @@ -2118,6 +2118,36 @@ for the emulated platofrm (see KVM_SET_DEVICE_ADDRESS), but before the CPU is
>> initally run.
>>
>>
>> +4.80 KVM_SET_DEVICE_ADDRESS
>> +
>> +Capability: KVM_CAP_SET_DEVICE_ADDRESS
>> +Architectures: arm
>> +Type: vm ioctl
>> +Parameters: struct kvm_device_address (in)
>> +Returns: 0 on success, -1 on error
>> +Errors:
>> + ENODEV: The device id is unknwown
>
> "unknown"
>
>> + ENXIO: Device not supported in configuration
>
> "in this configuration" ? (I'm guessing this is for "you tried to
> map a GIC when this CPU doesn't have a GIC" and similar errors?)
>
>> + E2BIG: Address outside of guest physical address space
>
> I would say "outside" rather than "outside of" here.
>
>> +
>> +struct kvm_device_address {
>> + __u32 id;
>> + __u64 addr;
>> +};
>> +
>> +Specify a device address in the guest's physical address space where guests
>> +can access emulated or directly exposed devices, which the host kernel needs
>> +to know about. The id field is an architecture specific identifier for a
>> +specific device.
>> +
>> +ARM divides the id field into two parts, a device ID and an address type id
>
> We should be consistent about whether ID is capitalised or not.
>
indeed
>> +specific to the individual device.
>> +
>> + bits: | 31 ... 16 | 15 ... 0 |
>> + field: | device id | addr type id |
>
> This doesn't say whether userspace is allowed to make this ioctl
> multiple times for the same device. This could be any of:
> * undefined behaviour
> * second call fails with some errno
> * second call overrides first one
>
I added an error condition EEXIST, but since this is trying to not be
arm-vgic specific this is really up to the individual device - maybe
we can have some polymorphic device that moves around later.
> It also doesn't say that you're supposed to call this after CREATE
> and before INIT of the irqchip. (Nor does it say what happens if
> you call it at some other time.)
>
same non-device specific argument as above.
Thanks,
-Christoffer
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