KVM: PPC: Book3S HV: Reserve POWER8 space in get/set_one_reg

Alex,

This reserves space in get/set_one_reg ioctl for the extra guest state needed for POWER8. It doesn't implement these at all, it just reserves them so that the ABI is defined now.

A few things to note here:

- POWER8 has 6 PMCs and an additional 2 SPMCs for the supervisor. Here I'm storing these 2 SPMCs in PMC7/8.

- This add *a lot* state for transactional memory. TM suspend mode, this is unavoidable, you can't simply roll back all transactions and store only the checkpointed state. I've added this all to get/set_one_reg (including GPRs) rather than creating a new ioctl which returns a struct kvm_regs like KVM_GET_REGS does. This means we if we need to extract the TM state, we are going to need a bucket load of IOCTLs. Hopefully most of the time this will not be needed as we can look at the MSR to see if TM is active and only grab them when needed.

- The TM state is offset bu 0x1000. Other than being bigger than the SPR space, it's fairly arbitrarily chose.

- For TM, I've done away with VMX and FP and created a single 64x128 bit VSX register space.

Alex: I'll add the documentation Documentation/virtual/kvm/api.txt if you're happy with all this.

Quoted 2 lines

- The TM state is offset bu 0x1000. Other than being bigger than

the

Quoted 1 line

SPR space, it's fairly arbitrarily chose.

Quoted 4 lines · Alexander Graf

Quoted 2 lines

- The TM state is offset bu 0x1000. Other than being bigger than

the

Quoted 1 line

SPR space, it's fairly arbitrarily chose.

Make it higher, just in case....

Quoted 6 lines · Michael Neuling

Alex,

This reserves space in get/set_one_reg ioctl for the extra guest state needed for POWER8. It doesn't implement these at all, it just reserves them so that the ABI is defined now.

Quoted 4 lines

A few things to note here:

- POWER8 has 6 PMCs and an additional 2 SPMCs for the supervisor. Here I'm storing these 2 SPMCs in PMC7/8.

Is this safe to do? Are we guaranteed that POWER9 or POWER10 doesn't introduce a real PMC7?

Quoted 10 lines

- This add *a lot* state for transactional memory. TM suspend mode, this is unavoidable, you can't simply roll back all transactions and store only the checkpointed state. I've added this all to get/set_one_reg (including GPRs) rather than creating a new ioctl which returns a struct kvm_regs like KVM_GET_REGS does. This means we if we need to extract the TM state, we are going to need a bucket load of IOCTLs. Hopefully most of the time this will not be needed as we can look at the MSR to see if TM is active and only grab them when needed.

If we find this to be a performance issue, we can always add a new ioctl that allows multiple ONE_REG accesses at a time. The only reason we don't have that yet is that bulk one_reg access hasn't happened in any performance critical path so far.

Quoted 5 lines

- The TM state is offset bu 0x1000. Other than being bigger than the SPR space, it's fairly arbitrarily chose.

Quoted 5 lines

- For TM, I've done away with VMX and FP and created a single 64x128 bit VSX register space.

Alex: I'll add the documentation Documentation/virtual/kvm/api.txt if you're happy with all this.

Looks perfectly reasonable to me :).

This reserves space in get/set_one_reg ioctl for the extra guest state needed for POWER8. It doesn't implement these at all, it just reserves them so that the ABI is defined now.

A few things to note here:

- This add *a lot* state for transactional memory. TM suspend mode, this is unavoidable, you can't simply roll back all transactions and store only the checkpointed state. I've added this all to get/set_one_reg (including GPRs) rather than creating a new ioctl which returns a struct kvm_regs like KVM_GET_REGS does. This means we if we need to extract the TM state, we are going to need a bucket load of IOCTLs. Hopefully most of the time this will not be needed as we can look at the MSR to see if TM is active and only grab them when needed. If this becomes a bottle neck in future we can add another ioctl to grab all this state in one go.

- The TM state is offset by 0x80000000.

- For TM, I've done away with VMX and FP and created a single 64x128 bit VSX register space.

- I've left a space of 1 (at 0x9c) since Paulus needs to add a value which applies to POWER7 as well.

Signed-off-by Michael Neuling<[email protected]>