[XenPPC] A bunch of questions - arch_vcpu, hcall/papr/hypercall

[Christian Ehrhardt <ehrhardt@xxxxxxxxxxxxxxxxxx>]

Hi everyone,
I have several issues where I need your help to understand xenppc so 
that I don't get lost in the code. I try to number the questions so no 
one can be overseen in the text.
1. arch_vcpu
I order to be able to save/restore performance sprs I need a per vcpu 
storage, because it only affects our architecture it seemed logic to put 
that into arch_vcpu (defined in include/asm-powerpc/domain.h). I 
searched for a while with grep, cscope, ... but unfortunately I can't 
find the initialization of the variables in the arch_vcpu struct. I 
found some initializations of the similar arch_domain in 
arch/powerpc/domain.c and the general vcpu initialization in 
common/domain.c.
The only related arch dependent init is in arch/powerpc/domain.c in the 
function alloc_vcpu_struct, but it looked to small for me because it 
only does alloc/memset zero.
I need to initialize my variables, so I welcome every hint where I could 
find (or create if really not existant) the initialization of the 
arch_vcpu part.
2. background hcall, hypercall, papr call
Sorry for the confusion jimi, but up to your last mails I don't even 
know that they are different things. I know the "xen hypercalls" from 
the xen docs, but can someone please describe (or point to a doc) what 
the other(s) is/are?
Whats the difference between them?
When do we use which kind of call in xenppc?
Hopefully I understand the suggestion of "ppc_md.enable_pmcs = 
xen_enable_pmcs;" from Jimi after that ;)
3. background hcall, hypercall, papr call - second one
I hope to get a "I see" with the answer to number two, but it would be 
really helpful to have some brief cookbook like instructions that 
describe for the different calls what is and where it need to be 
implemented - look there for an example.
Here a wrong example what I hope to get ;)
Xen Hypercall foo_op:
0. Xen & Domain set up an event channel foo_chan - look in 
xen/bar/file.c & arch/powerpc/platforms/xen/hcall.c
1. The Domain needs to setup a irq vector for the irq of the event 
channel - look arch/powerpc/foo.c
2. Xen uses the event channel to notify the domain - look 
xen/arch/powerpc/foo.c
papr hcall XY:
1. ...


--

Grüsse / regards, 
Christian Ehrhardt
IBM Linux Technology Center, Open Virtualization
+49 7031/16-3385
Ehrhardt@xxxxxxxxxxxxxxxxxxx
Ehrhardt@xxxxxxxxxx

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