Re: [PATCH v6 00/17] KVM: PPC: Book3S HV: add XIVE native exploitation mode

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On 4/30/19 12:11 PM, Paul Mackerras wrote:
> On Thu, Apr 18, 2019 at 12:39:25PM +0200, Cédric Le Goater wrote:
>> On the POWER9 processor, the XIVE interrupt controller can control
>> interrupt sources using MMIOs to trigger events, to EOI or to turn off
>> the sources. Priority management and interrupt acknowledgment is also
>> controlled by MMIO in the CPU presenter sub-engine.
>>
>> PowerNV/baremetal Linux runs natively under XIVE but sPAPR guests need
>> special support from the hypervisor to do the same. This is called the
>> XIVE native exploitation mode and today, it can be activated under the
>> PowerPC Hypervisor, pHyp. However, Linux/KVM lacks XIVE native support
>> and still offers the old interrupt mode interface using a KVM device
>> implementing the XICS hcalls over XIVE.
>>
>> The following series is proposal to add the same support under KVM.
>>
>> A new KVM device is introduced for the XIVE native exploitation
>> mode. It reuses most of the XICS-over-XIVE glue implementation
>> structures which are internal to KVM but has a completely different
>> interface. A set of KVM device ioctls provide support for the
>> hypervisor calls, all handled in QEMU, to configure the sources and
>> the event queues. From there, all interrupt control is transferred to
>> the guest which can use MMIOs.
>>
>> These MMIO regions (ESB and TIMA) are exposed to guests in QEMU,
>> similarly to VFIO, and the associated VMAs are populated dynamically
>> with the appropriate pages using a fault handler. These are now
>> implemented using mmap()s of the KVM device fd.
>>
>> Migration has its own specific needs regarding memory. The patchset
>> provides a specific control to quiesce XIVE before capturing the
>> memory. The save and restore of the internal state is based on the
>> same ioctls used for the hcalls.
>>
>> On a POWER9 sPAPR machine, the Client Architecture Support (CAS)
>> negotiation process determines whether the guest operates with a
>> interrupt controller using the XICS legacy model, as found on POWER8,
>> or in XIVE exploitation mode. Which means that the KVM interrupt
>> device should be created at run-time, after the machine has started.
>> This requires extra support from KVM to destroy KVM devices. It is
>> introduced at the end of the patchset and requires some attention.
>>
>> This is based on Linux 5.1-rc5 and is a candidate for 5.2. The OPAL
>> patches have been merged now.
> 
> Thanks, patch series applied to my kvm-ppc-next tree.  I added two
> patches of mine on top to make sure we exclude other execution paths
> in the device release method, and to clear the escalation interrupt
> hardware pointers on release.  I also modified your last patch to free
> the xive structures in book3s.c rather than powerpc.c in order to fix
> compilation for Book E configs.

OK. I have one minor cleanup removing bogus checks in the release method 
of the KVM device. 

Thanks,

C.



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