[v5,00/12] x86: major paravirt cleanup

Message

Jürgen Groß March 8, 2021, 12:28 p.m. UTC

This is a major cleanup of the paravirt infrastructure aiming at
eliminating all custom code patching via paravirt patching.

This is achieved by using ALTERNATIVE instead, leading to the ability
to give objtool access to the patched in instructions.

In order to remove most of the 32-bit special handling from pvops the
time related operations are switched to use static_call() instead.

At the end of this series all paravirt patching has to do is to
replace indirect calls with direct ones. In a further step this could
be switched to static_call(), too.

Changes in V5:
- patches 1-5 of V4 dropped, as already applied
- new patches 1+3
- fixed patch 2
- split V4 patch 8 into patches 4+5
- use flag byte instead of negative feature bit for "not feature"

Changes in V4:
- fixed several build failures
- removed objtool patch, as objtool patches are in tip now
- added patch 1 for making usage of static_call easier
- even more cleanup

Changes in V3:
- added patches 7 and 12
- addressed all comments

Changes in V2:
- added patches 5-12

Juergen Gross (12):
  staticcall: move struct static_call_key definition to
    static_call_types.h
  x86/paravirt: switch time pvops functions to use static_call()
  x86/alternative: drop feature parameter from ALTINSTR_REPLACEMENT()
  x86/alternative: support not-feature
  x86/alternative: support ALTERNATIVE_TERNARY
  x86: add new features for paravirt patching
  x86/paravirt: remove no longer needed 32-bit pvops cruft
  x86/paravirt: simplify paravirt macros
  x86/paravirt: switch iret pvops to ALTERNATIVE
  x86/paravirt: add new macros PVOP_ALT* supporting pvops in
    ALTERNATIVEs
  x86/paravirt: switch functions with custom code to ALTERNATIVE
  x86/paravirt: have only one paravirt patch function

 arch/arm/include/asm/paravirt.h               |  14 +-
 arch/arm/kernel/paravirt.c                    |   9 +-
 arch/arm64/include/asm/paravirt.h             |  14 +-
 arch/arm64/kernel/paravirt.c                  |  13 +-
 arch/x86/Kconfig                              |   1 +
 arch/x86/entry/entry_32.S                     |   4 +-
 arch/x86/entry/entry_64.S                     |   2 +-
 arch/x86/include/asm/alternative-asm.h        |  10 +
 arch/x86/include/asm/alternative.h            |  28 ++-
 arch/x86/include/asm/cpufeature.h             |   2 +
 arch/x86/include/asm/cpufeatures.h            |   2 +
 arch/x86/include/asm/irqflags.h               |   7 +-
 arch/x86/include/asm/mshyperv.h               |   2 +-
 arch/x86/include/asm/paravirt.h               | 167 +++++++-------
 arch/x86/include/asm/paravirt_types.h         | 210 +++++++-----------
 arch/x86/kernel/Makefile                      |   3 +-
 arch/x86/kernel/alternative.c                 |  37 ++-
 arch/x86/kernel/asm-offsets.c                 |   7 -
 arch/x86/kernel/cpu/vmware.c                  |   5 +-
 arch/x86/kernel/kvm.c                         |   2 +-
 arch/x86/kernel/kvmclock.c                    |   2 +-
 arch/x86/kernel/paravirt-spinlocks.c          |   9 +
 arch/x86/kernel/paravirt.c                    |  78 ++-----
 arch/x86/kernel/paravirt_patch.c              |  99 ---------
 arch/x86/kernel/tsc.c                         |   2 +-
 arch/x86/xen/enlighten_pv.c                   |   4 +-
 arch/x86/xen/time.c                           |  11 +-
 drivers/xen/time.c                            |   3 +-
 include/linux/static_call.h                   |  18 --
 include/linux/static_call_types.h             |  18 ++
 tools/include/linux/static_call_types.h       |  18 ++
 tools/objtool/arch/x86/include/arch/special.h |   6 +-
 32 files changed, 339 insertions(+), 468 deletions(-)
 delete mode 100644 arch/x86/kernel/paravirt_patch.c

Comments

Peter Zijlstra March 8, 2021, 4:31 p.m. UTC | #1

On Mon, Mar 08, 2021 at 01:28:32PM +0100, Juergen Gross wrote:
> This is a major cleanup of the paravirt infrastructure aiming at
> eliminating all custom code patching via paravirt patching.
> 
> This is achieved by using ALTERNATIVE instead, leading to the ability
> to give objtool access to the patched in instructions.
> 
> In order to remove most of the 32-bit special handling from pvops the
> time related operations are switched to use static_call() instead.
> 
> At the end of this series all paravirt patching has to do is to
> replace indirect calls with direct ones. In a further step this could
> be switched to static_call(), too.

Acked-by: Peter Zijlstra (Intel) <[e-mail]>

I've rebased my objtool/retpoline branch on top of this, will post
if/when this hits tip. Negative alternative works like a charm.