Hi Paolo and Gleb,

The attached file is a preliminary version of AMD vPMU support for KVM. 
Currently I am working on a formal patch set; but realized that there 
are some design choice to make (see below). I thought it is better to 
send it out now, asking for your comments before sending out patchset v1.

If you are OK with current approach, please let me know. Otherwise 
please share your suggestions/comments on the design choice (see 
suggestions below). I will send out split patch set soon.

Thanks,
-Wei

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1. OBJECTIVE
To enable PMU for guest VMs running on AMD host. Currently only software 
events are supported for AMD guest VMs. This is useless to profile guest 
VM on AMD systems.

2. CURRENT DESIGN
The design is similar to existing vPMU support. Many data structures 
such as "struct kvm_pmc" and "struct kvm_pmu" are re-used for this design.

Original pmu.c code was designed with Intel PMU in mind. To avoid the 
confusion, the current design converts existing pmu.c into intel-pmu.c 
and create a similar code, named amd-pmu.c. PMU function calls in x86.c 
are then dispatched via function pointers (i.e. struct kvm_pmu_ops). The 
initial setup is done in kvm_pmu_arch_init().

3. STATUS
I have briefly tested using AMD machine and the profiling data seems to 
be fairly accurate. With that said, more tests are required especially 
on PMI and extensive HW perf events.

4. DESIGN QUESTIONS
The current design is described in (2). However it is not perfect, 
especially due to the code similarity between intel-pmu.c and amd-pmu.c.

I have other ideas listed below. Please review and give some suggestion:

(a) Merge intel-pmu.c and amd-pmu.c into pmu.c
* PMU will probe the architecture first before first usage;
* It will still use function pointers to dispatch global functions (e.g. 
kvm_pmu_reset);
* For static functions that are the same (e.g. pmc_is_gp), we will use 
the same copy;
* For static functions that are slightly different (e.g. 
global_idx_to_pmc), we will use a shared version with if-else statement, 
depending on Intel or AMD.

I think this approach is quite acceptable, except that there will be 
many if-else in the code. Not clean enough.

(b) Convert intel-pmu.c => vmx.c and convert amd-pmu.c => svm.c
* PMU function pointers will be created in kvm_x86_ops;
* The entry functions will be created inside vmx.c and svm.c respectively;
* There might be common functions defined in pmu.c.

This design is viable too. But to be honest, it is a bit messy compared 
with (a).

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