Re: [PATCH v3 00/13] xen: drop hypercall function tables

[Jan Beulich <jbeulich@xxxxxxxx>]

On 09.12.2021 10:10, Juergen Gross wrote:
> On 09.12.21 10:05, Jan Beulich wrote:
>> On 08.12.2021 16:55, Juergen Gross wrote:
>>> In order to avoid indirect function calls on the hypercall path as
>>> much as possible this series is removing the hypercall function tables
>>> and is replacing the hypercall handler calls via the function array
>>> by automatically generated call macros.
>>>
>>> Another by-product of generating the call macros is the automatic
>>> generating of the hypercall handler prototypes from the same data base
>>> which is used to generate the macros.
>>>
>>> This has the additional advantage of using type safe calls of the
>>> handlers and to ensure related handler (e.g. PV and HVM ones) share
>>> the same prototypes.
>>>
>>> A very brief performance test (parallel build of the Xen hypervisor
>>> in a 6 vcpu guest) showed a very slim improvement (less than 1%) of
>>> the performance with the patches applied. The test was performed using
>>> a PV and a PVH guest.
>>>
>>> Changes in V2:
>>> - new patches 6, 14, 15
>>> - patch 7: support hypercall priorities for faster code
>>> - comments addressed
>>>
>>> Changes in V3:
>>> - patches 1 and 4 removed as already applied
>>> - comments addressed
>>>
>>> Juergen Gross (13):
>>>    xen: move do_vcpu_op() to arch specific code
>>>    xen: harmonize return types of hypercall handlers
>>>    xen: don't include asm/hypercall.h from C sources
>>>    xen: include compat/platform.h from hypercall.h
>>>    xen: generate hypercall interface related code
>>>    xen: use generated prototypes for hypercall handlers
>>>    x86/pv-shim: don't modify hypercall table
>>>    xen/x86: don't use hypercall table for calling compat hypercalls
>>>    xen/x86: call hypercall handlers via generated macro
>>>    xen/arm: call hypercall handlers via generated macro
>>>    xen/x86: add hypercall performance counters for hvm, correct pv
>>>    xen: drop calls_to_multicall performance counter
>>>    tools/xenperf: update hypercall names
>>
>> It's not easy to tell which, if any, of the later patches are fully
>> independent of earlier ones and could go in ahead of those awaiting
>> further acks. Do you have any suggestion there, or should we wait
>> until things can be applied in order?
> 
> I think all but the last patch should be applied in order. The last one
> obviously can be applied at any time.

Hmm, I think 11 and 12 are fine to go ahead as well; I actually need them
for some immediate purpose and hence I did pull them (but nothing else)
into my local tree, without observing issues.

Jan