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[v2,0/7] Removing support for 32bit KVM/arm host

Message ID 20200324103350.138077-1-maz@kernel.org (mailing list archive)
Headers show
Series Removing support for 32bit KVM/arm host | expand

Message

Marc Zyngier March 24, 2020, 10:33 a.m. UTC 
KVM/arm was merged just over 7 years ago, and has lived a very quiet
life so far. It mostly works if you're prepared to deal with its
limitations, it has been a good prototype for the arm64 version,
but it suffers a few problems:

- It is incomplete (no debug support, no PMU)
- It hasn't followed any of the architectural evolutions
- It has zero^W very few users (I don't count myself here)
- It is more and more getting in the way of new arm64 developments

There has been quite a bit of discussion (see [1]) on whether we were
depriving users of something they were depending on. Most people
didn't object, and actually supported the removal. A few people *did*
object to the removal:

- Takashi uses it on a regular basis for developments
- Daniel uses it as well, although he doesn't depend on it
- Marek and Bartlomiej said that Samsung use it internally, without
  any description of their usage model

Alghouth I can really sympathetize with people above, I still don't
think we should keep the 32bit port artificially alive for the sake of
it, specially considering that the whole of the 32bit architecture is
in best effort, maintenance mode. I'd rather drop KVM support now,
while it is still in a decent shape, rather than seeing it bit-rot
like it happened for ia64. I also plan to keep maintaining it in the
various stable kernels, up to (and including) 5.6.

To reiterate: 32bit guest support for arm64 stays, of course. Only
32bit host goes. Once this is merged, I plan to move virt/kvm/arm to
arm64, and cleanup all the now unnecessary abstractions.

The patches have been generated with the -D option to avoid spamming
everyone with huge diffs, and there is a kvm-arm/goodbye branch in
my kernel.org repository.

* From v1:
  - Rebased on top of kvmarm/next
  - Simplified the HYP vector replacement code
  - Updated the MAINTAINERS file
  - Collected Acks

[1] https://lore.kernel.org/linux-arm-kernel/20200210141324.21090-1-maz@kernel.org/

Marc Zyngier (7):
  arm: Unplug KVM from the build system
  arm: Remove KVM from config files
  arm: Remove 32bit KVM host support
  arm: Remove HYP/Stage-2 page-table support
  arm: Remove GICv3 vgic compatibility macros
  arm: Remove the ability to set HYP vectors outside of the decompressor
  MAINTAINERS: RIP KVM/arm

 Documentation/virt/kvm/arm/hyp-abi.rst |    5 +
 MAINTAINERS                            |    5 +-
 arch/arm/Kconfig                       |    2 -
 arch/arm/Makefile                      |    1 -
 arch/arm/configs/axm55xx_defconfig     |    2 -
 arch/arm/include/asm/arch_gicv3.h      |  114 --
 arch/arm/include/asm/kvm_arm.h         |  239 ----
 arch/arm/include/asm/kvm_asm.h         |   77 --
 arch/arm/include/asm/kvm_coproc.h      |   36 -
 arch/arm/include/asm/kvm_emulate.h     |  372 ------
 arch/arm/include/asm/kvm_host.h        |  457 --------
 arch/arm/include/asm/kvm_hyp.h         |  127 ---
 arch/arm/include/asm/kvm_mmu.h         |  435 -------
 arch/arm/include/asm/kvm_ras.h         |   14 -
 arch/arm/include/asm/pgtable-3level.h  |   20 -
 arch/arm/include/asm/pgtable.h         |    9 -
 arch/arm/include/asm/sections.h        |    6 +-
 arch/arm/include/asm/stage2_pgtable.h  |   75 --
 arch/arm/include/asm/virt.h            |   17 -
 arch/arm/include/uapi/asm/kvm.h        |  314 -----
 arch/arm/kernel/asm-offsets.c          |   11 -
 arch/arm/kernel/hyp-stub.S             |   39 +-
 arch/arm/kernel/vmlinux-xip.lds.S      |    8 -
 arch/arm/kernel/vmlinux.lds.S          |    8 -
 arch/arm/kernel/vmlinux.lds.h          |   10 -
 arch/arm/kvm/Kconfig                   |   59 -
 arch/arm/kvm/Makefile                  |   43 -
 arch/arm/kvm/coproc.c                  | 1455 ------------------------
 arch/arm/kvm/coproc.h                  |  130 ---
 arch/arm/kvm/coproc_a15.c              |   39 -
 arch/arm/kvm/coproc_a7.c               |   42 -
 arch/arm/kvm/emulate.c                 |  166 ---
 arch/arm/kvm/guest.c                   |  387 -------
 arch/arm/kvm/handle_exit.c             |  175 ---
 arch/arm/kvm/hyp/Makefile              |   34 -
 arch/arm/kvm/hyp/banked-sr.c           |   70 --
 arch/arm/kvm/hyp/cp15-sr.c             |   72 --
 arch/arm/kvm/hyp/entry.S               |  121 --
 arch/arm/kvm/hyp/hyp-entry.S           |  295 -----
 arch/arm/kvm/hyp/s2-setup.c            |   22 -
 arch/arm/kvm/hyp/switch.c              |  242 ----
 arch/arm/kvm/hyp/tlb.c                 |   68 --
 arch/arm/kvm/hyp/vfp.S                 |   57 -
 arch/arm/kvm/init.S                    |  157 ---
 arch/arm/kvm/interrupts.S              |   36 -
 arch/arm/kvm/irq.h                     |   16 -
 arch/arm/kvm/reset.c                   |   86 --
 arch/arm/kvm/trace.h                   |   86 --
 arch/arm/kvm/vgic-v3-coproc.c          |   27 -
 arch/arm/mach-exynos/Kconfig           |    2 +-
 arch/arm/mm/mmu.c                      |   26 -
 51 files changed, 16 insertions(+), 6300 deletions(-)
 delete mode 100644 arch/arm/include/asm/kvm_arm.h
 delete mode 100644 arch/arm/include/asm/kvm_asm.h
 delete mode 100644 arch/arm/include/asm/kvm_coproc.h
 delete mode 100644 arch/arm/include/asm/kvm_emulate.h
 delete mode 100644 arch/arm/include/asm/kvm_host.h
 delete mode 100644 arch/arm/include/asm/kvm_hyp.h
 delete mode 100644 arch/arm/include/asm/kvm_mmu.h
 delete mode 100644 arch/arm/include/asm/kvm_ras.h
 delete mode 100644 arch/arm/include/asm/stage2_pgtable.h
 delete mode 100644 arch/arm/include/uapi/asm/kvm.h
 delete mode 100644 arch/arm/kvm/Kconfig
 delete mode 100644 arch/arm/kvm/Makefile
 delete mode 100644 arch/arm/kvm/coproc.c
 delete mode 100644 arch/arm/kvm/coproc.h
 delete mode 100644 arch/arm/kvm/coproc_a15.c
 delete mode 100644 arch/arm/kvm/coproc_a7.c
 delete mode 100644 arch/arm/kvm/emulate.c
 delete mode 100644 arch/arm/kvm/guest.c
 delete mode 100644 arch/arm/kvm/handle_exit.c
 delete mode 100644 arch/arm/kvm/hyp/Makefile
 delete mode 100644 arch/arm/kvm/hyp/banked-sr.c
 delete mode 100644 arch/arm/kvm/hyp/cp15-sr.c
 delete mode 100644 arch/arm/kvm/hyp/entry.S
 delete mode 100644 arch/arm/kvm/hyp/hyp-entry.S
 delete mode 100644 arch/arm/kvm/hyp/s2-setup.c
 delete mode 100644 arch/arm/kvm/hyp/switch.c
 delete mode 100644 arch/arm/kvm/hyp/tlb.c
 delete mode 100644 arch/arm/kvm/hyp/vfp.S
 delete mode 100644 arch/arm/kvm/init.S
 delete mode 100644 arch/arm/kvm/interrupts.S
 delete mode 100644 arch/arm/kvm/irq.h
 delete mode 100644 arch/arm/kvm/reset.c
 delete mode 100644 arch/arm/kvm/trace.h
 delete mode 100644 arch/arm/kvm/vgic-v3-coproc.c

Comments

Quentin Perret March 26, 2020, 10:17 a.m. UTC | #1 
Hi Marc,

On Tuesday 24 Mar 2020 at 10:33:43 (+0000), Marc Zyngier wrote:
> Marc Zyngier (7):
>   arm: Unplug KVM from the build system
>   arm: Remove KVM from config files
>   arm: Remove 32bit KVM host support
>   arm: Remove HYP/Stage-2 page-table support
>   arm: Remove GICv3 vgic compatibility macros
>   arm: Remove the ability to set HYP vectors outside of the decompressor
>   MAINTAINERS: RIP KVM/arm

I've been staring at these patches for some time now and all looks good
to me. So, for the entire series:

Reviewed-by: Quentin Perret <qperret@google.com>

FWIW, as mentioned in a previous thread, I'm currently working with Will
on an extension of KVM to support guest isolation, and the arm32 port
was unfortunately making it really hard to do intrusive changes, so this
is much appreciated!

Thanks,
Quentin