[v3,0/2] Clean the policy manipulation path in domain creation

Message

Alejandro Vallejo May 23, 2024, 9:41 a.m. UTC

v2 -> v3:
  * Style adjustments
  * Revert of loop index scope refactors

v1 -> v2:
  * Removed xc_cpu_policy from xenguest.h (dropped v1/patch1)
  * Added accessors for xc_cpu_policy so the serialised form can be extracted.
  * Modified xen-cpuid to use accessors.

==== Original cover letter ====

In the context of creating a domain, we currently issue a lot of hypercalls
redundantly while populating its CPU policy; likely a side effect of
organic growth more than anything else.

However, the worst part is not the overhead (this is a glacially cold
path), but the insane amounts of boilerplate that make it really hard to
pick apart what's going on. One major contributor to this situation is the
fact that what's effectively "setup" and "teardown" phases in policy
manipulation are not factored out from the functions that perform said
manipulations, leading to the same getters and setter being invoked many
times, when once each would do.

Another big contributor is the code being unaware of when a policy is
serialised and when it's not.

This patch attempts to alleviate this situation, yielding over 200 LoC
reduction.

Patch 1: Mechanical change. Makes xc_cpu_policy_t public so it's usable
         from clients of libxc/libxg.
Patch 2: Changes the (de)serialization wrappers in xenguest so they always
         serialise to/from the internal buffers of xc_cpu_policy_t. The
         struct is suitably expanded to hold extra information required.
Patch 3: Performs the refactor of the policy manipulation code so that it
         follows a strict: PULL_POLICIES, MUTATE_POLICY (n times), PUSH_POLICY.


Subject: [PATCH v3 0/2] *** SUBJECT HERE ***

*** BLURB HERE ***

Alejandro Vallejo (2):
  tools/xg: Streamline cpu policy serialise/deserialise calls
  tools/xg: Clean up xend-style overrides for CPU policies

 tools/include/xenguest.h            |   8 +-
 tools/libs/guest/xg_cpuid_x86.c     | 530 ++++++++++------------------
 tools/libs/guest/xg_private.h       |   2 +
 tools/libs/guest/xg_sr_common_x86.c |  56 ++-
 tools/misc/xen-cpuid.c              |  41 +--
 5 files changed, 234 insertions(+), 403 deletions(-)