On 2/5/19 6:28 AM, David Gibson wrote:
> On Mon, Feb 04, 2019 at 12:30:39PM +0100, Cédric Le Goater wrote:
>> On 2/4/19 5:45 AM, David Gibson wrote:
>>> On Mon, Jan 07, 2019 at 07:43:18PM +0100, Cédric Le Goater wrote:
>>>> This will let the guest create a memory mapping to expose the ESB MMIO
>>>> regions used to control the interrupt sources, to trigger events, to
>>>> EOI or to turn off the sources.
>>>>
>>>> Signed-off-by: Cédric Le Goater <clg@xxxxxxxx>
>>>> ---
>>>> arch/powerpc/include/uapi/asm/kvm.h | 4 ++
>>>> arch/powerpc/kvm/book3s_xive_native.c | 97 +++++++++++++++++++++++++++
>>>> 2 files changed, 101 insertions(+)
>>>>
>>>> diff --git a/arch/powerpc/include/uapi/asm/kvm.h b/arch/powerpc/include/uapi/asm/kvm.h
>>>> index 8c876c166ef2..6bb61ba141c2 100644
>>>> --- a/arch/powerpc/include/uapi/asm/kvm.h
>>>> +++ b/arch/powerpc/include/uapi/asm/kvm.h
>>>> @@ -675,4 +675,8 @@ struct kvm_ppc_cpu_char {
>>>> #define KVM_XICS_PRESENTED (1ULL << 43)
>>>> #define KVM_XICS_QUEUED (1ULL << 44)
>>>>
>>>> +/* POWER9 XIVE Native Interrupt Controller */
>>>> +#define KVM_DEV_XIVE_GRP_CTRL 1
>>>> +#define KVM_DEV_XIVE_GET_ESB_FD 1
>>>
>>> Introducing a new FD for ESB and TIMA seems overkill. Can't you get
>>> to both with an mmap() directly on the xive device fd? Using the
>>> offset to distinguish which one to map, obviously.
>>
>> The page offset would define some sort of user API. It seems feasible.
>> But I am not sure this would be practical in the future if we need to
>> tune the length.
>
> Um.. why not? I mean, yes the XIVE supports rather a lot of
> interrupts, but we have 64-bits of offset we can play with - we can
> leave room for billions of ESB slots and still have room for billions
> of VPs.
So the first 4 pages could be the TIMA pages and then would come
the pages for the interrupt ESBs. I think that we can have different
vm_fault handler for each mapping.
I wonder how this will work out with pass-through. As Paul said in
a previous email, it would be better to let QEMU request a new
mapping to handle the ESB pages of the device being passed through.
I guess this is not a special case, just another offset and length.
I will give it a try.
Thanks,
C.
