[PATCH 00/26] KVM: vfio: Hide KVM internals from others

Sean Christopherson
2023-09-16T00:32:45Z

This is a borderline RFC series to hide KVM's internals from the rest of
the kernel, where "internals" means data structures, enums, #defines,
APIs, etc. that are intended to be KVM-only, but are exposed everywhere
due to kvm_host.h (and other headers) living in the global include paths.

The motiviation for hiding KVM's internals is to allow *safely* loading a
"new" KVM module without having to reboot the host. Where "new" doesn't
have to be strictly newer, just a different incarnation of KVM. Hiding
KVM's internals means those assets can change across KVM instances without
breaking things, e.g. would allow modifying the layout of struct kvm_vcpu
to introduce new fields related to a new feature or mitigation for hardware
bugs.

The end goal for all of this is to allow loading and running multiple
instances of KVM (the module) simultaneously on a single host, e.g. to
deploy fixes, mitigations, and/or new features without having to drain
all VMs from the host.

For now, the immediate goal is to get KVM to a state where KVM x86 doesn't
expose anything to the broader world that isn't intended for external
consumption, e.g. the page write-tracking APIs used by KVM-GT.

I say this is borderline RFC because I don't think I've "formally" proposed
the idea of hiding KVM internals before now. I decided not to tag this RFC
because the changes ended up being not _that_ invasive, and everything
before the last six patches is worthwhile even if hiding internals is
ultimately rejected (IMO).

This would ideally be ~5 separate series, and I certainly have no objection
if that's how we want to get this stuff merged. E.g. (1) VFIO cleanups,
(2) drop HAVE_KVM, (3) clean up makefiles, (4) x86 perf cleanup, and
(5) final push for hiding state. The HAVE_KVM and virt/kvm include stuff
isn't strictly necessary, but I included them here because they're
relatively minor (in the grand scheme).

We've explore several alternatives to the #ifdef __KVM__ approach, and
they all sucked, hard. What I really wanted (and still want) to do, is to
bury the bulk of kvm_host.h (and other KVM headers) in virt/kvm, but every
attempt to do that ended in flames. Even with the __KVM__ guards in place,
each architecture's kvm_host.h is too intertwined with the common kvm_host.h,
and trying to extract small-ish pieces just doesn't work (each patch
inevitably snowballed into a gigantic beast).

The other idea we considered (which I thought of, and feel dirty for even
proposing it internally), is to move all headers under virt/kvm, add
virt/kvm/include to the global header path, and then have KVM x86 omit
virt/kvm/include when configured to hide KVM internals. I hate this idea
because it sets a bad precedent, and requires a lot of file movement
without providing any benefit to other architectures. E.g. I hope that
guarding KVM internals with #ifdef __KVM__ will allow us to slowly clean
things up so that some day KVM only exposes a handful of APIs to the rest
of the kernel (probably a pipe dream).

Anish Ghulati (1):
KVM: arm64: Move arm_{psci,hypercalls}.h to an internal KVM path

Sean Christopherson (25):
vfio: Wrap KVM helpers with CONFIG_KVM instead of CONFIG_HAVE_KVM
vfio: Move KVM get/put helpers to colocate it with other KVM related
code
virt: Declare and define vfio_file_set_kvm() iff CONFIG_KVM is enabled
vfio: Add struct to hold KVM assets and dedup group vs. iommufd code
vfio: KVM: Pass get/put helpers from KVM to VFIO, don't do circular
lookup
KVM: Drop CONFIG_KVM_VFIO and just look at KVM+VFIO
x86/idt: Wrap KVM logic with CONFIG_KVM instead of CONFIG_HAVE_KVM
KVM: x86: Stop selecting and depending on HAVE_KVM
KVM: arm64: Stop selecting and depending on HAVE_KVM
KVM: s390: Stop selecting and depending on HAVE_KVM
KVM: MIPS: Make HAVE_KVM a MIPS-only Kconfig
KVM: arm64: Include KVM headers to get forward declarations
KVM: arm64: Move ARM specific headers in include/kvm to arch directory
KVM: Move include/kvm/iodev.h to include/linux as kvm_iodev.h
KVM: MIPS: Stop adding virt/kvm to the arch include path
KVM: PPC: Stop adding virt/kvm to the arch include path
KVM: s390: Stop adding virt/kvm to the arch include path
KVM: Standardize include paths across all architectures
perf/x86: KVM: Have perf define a dedicated struct for getting guest
PEBS data
entry/kvm: Drop @vcpu param from arch_xfer_to_guest_mode_handle_work()
entry/kvm: KVM: Move KVM details related to signal/-EINTR into KVM
proper
KVM: arm64: Move and consolidate "public" functions in asm/kvm_host.h
powerpc/xics: Move declaration of xics_wake_cpu() out of kvm_ppc.h
KVM: PPC: Rearrange code in kvm_ppc.h to isolate "public" information
KVM: Hide KVM internal data structures and values from kernel at-large

MAINTAINERS | 1 -
arch/arm64/Kconfig | 1 -
.../arm64/include/asm/kvm_arch_timer.h | 2 +
arch/arm64/include/asm/kvm_emulate.h | 3 +
arch/arm64/include/asm/kvm_host.h | 57 ++--
arch/arm64/include/asm/kvm_mmu.h | 4 +
.../arm64/include/asm/kvm_pmu.h | 2 +
.../arm64/include/asm/kvm_vgic.h | 2 +-
arch/arm64/kernel/asm-offsets.c | 2 +
arch/arm64/kvm/Kconfig | 2 -
arch/arm64/kvm/Makefile | 2 -
arch/arm64/kvm/arch_timer.c | 5 +-
arch/arm64/kvm/arm.c | 9 +-
{include => arch/arm64}/kvm/arm_hypercalls.h | 0
{include => arch/arm64}/kvm/arm_psci.h | 0
arch/arm64/kvm/guest.c | 2 +-
arch/arm64/kvm/handle_exit.c | 2 +-
arch/arm64/kvm/hyp/Makefile | 4 +-
arch/arm64/kvm/hyp/include/hyp/switch.h | 4 +-
arch/arm64/kvm/hyp/nvhe/Makefile | 3 +-
arch/arm64/kvm/hyp/nvhe/switch.c | 4 +-
arch/arm64/kvm/hyp/vhe/Makefile | 2 +-
arch/arm64/kvm/hyp/vhe/switch.c | 4 +-
arch/arm64/kvm/hypercalls.c | 4 +-
arch/arm64/kvm/pmu-emul.c | 6 +-
arch/arm64/kvm/psci.c | 4 +-
arch/arm64/kvm/pvtime.c | 2 +-
arch/arm64/kvm/reset.c | 3 +-
arch/arm64/kvm/trace_arm.h | 2 +-
arch/arm64/kvm/trng.c | 2 +-
arch/arm64/kvm/vgic/vgic-debug.c | 2 +-
arch/arm64/kvm/vgic/vgic-init.c | 2 +-
arch/arm64/kvm/vgic/vgic-irqfd.c | 2 +-
arch/arm64/kvm/vgic/vgic-kvm-device.c | 2 +-
arch/arm64/kvm/vgic/vgic-mmio-v2.c | 4 +-
arch/arm64/kvm/vgic/vgic-mmio-v3.c | 4 +-
arch/arm64/kvm/vgic/vgic-mmio.c | 6 +-
arch/arm64/kvm/vgic/vgic-v2.c | 2 +-
arch/arm64/kvm/vgic/vgic-v3.c | 2 +-
arch/mips/include/asm/kvm_host.h | 5 +-
arch/mips/kernel/asm-offsets.c | 2 +
arch/mips/kvm/Kconfig | 3 +
arch/mips/kvm/Makefile | 2 -
arch/powerpc/include/asm/kvm_book3s.h | 3 +
arch/powerpc/include/asm/kvm_book3s_64.h | 2 +
arch/powerpc/include/asm/kvm_booke.h | 4 +
arch/powerpc/include/asm/kvm_host.h | 7 +-
arch/powerpc/include/asm/kvm_ppc.h | 306 +++++++++---------
arch/powerpc/include/asm/xics.h | 3 +
arch/powerpc/kernel/asm-offsets.c | 1 +
arch/powerpc/kvm/Kconfig | 1 -
arch/powerpc/kvm/Makefile | 2 -
arch/powerpc/kvm/mpic.c | 2 +-
arch/riscv/include/asm/kvm_host.h | 3 +
arch/riscv/kernel/asm-offsets.c | 1 +
arch/riscv/kvm/Makefile | 2 -
arch/riscv/kvm/aia_aplic.c | 2 +-
arch/riscv/kvm/aia_imsic.c | 2 +-
arch/riscv/kvm/vcpu.c | 2 +-
arch/s390/Kconfig | 1 -
arch/s390/include/asm/kvm_host.h | 7 +-
arch/s390/kernel/asm-offsets.c | 1 +
arch/s390/kvm/Kconfig | 2 -
arch/s390/kvm/Makefile | 2 -
arch/x86/Kconfig | 1 -
arch/x86/events/core.c | 5 +-
arch/x86/events/intel/core.c | 18 +-
arch/x86/events/perf_event.h | 3 +-
arch/x86/include/asm/hardirq.h | 2 +-
arch/x86/include/asm/idtentry.h | 2 +-
arch/x86/include/asm/irq.h | 2 +-
arch/x86/include/asm/irq_vectors.h | 2 +-
arch/x86/include/asm/kvm_host.h | 12 +-
arch/x86/include/asm/perf_event.h | 12 +-
arch/x86/kernel/idt.c | 2 +-
arch/x86/kernel/irq.c | 4 +-
arch/x86/kvm/Kconfig | 3 -
arch/x86/kvm/Makefile | 1 -
arch/x86/kvm/i8254.h | 2 +-
arch/x86/kvm/ioapic.h | 2 +-
arch/x86/kvm/irq.h | 2 +-
arch/x86/kvm/lapic.h | 2 +-
arch/x86/kvm/vmx/pmu_intel.c | 16 +-
arch/x86/kvm/vmx/vmx.c | 11 +-
arch/x86/kvm/vmx/vmx.h | 2 +-
arch/x86/kvm/x86.c | 3 +-
drivers/s390/crypto/vfio_ap_drv.c | 1 +
drivers/s390/crypto/vfio_ap_ops.c | 2 +
drivers/vfio/device_cdev.c | 9 +-
drivers/vfio/group.c | 18 +-
drivers/vfio/vfio.h | 26 +-
drivers/vfio/vfio_main.c | 139 ++++----
include/linux/entry-kvm.h | 10 +-
include/linux/kvm_host.h | 17 +-
include/{kvm/iodev.h => linux/kvm_iodev.h} | 0
include/linux/kvm_types.h | 3 +
include/linux/vfio.h | 6 +-
include/trace/events/kvm.h | 5 +
kernel/entry/kvm.c | 13 +-
scripts/gdb/linux/constants.py.in | 2 +-
scripts/gdb/linux/interrupts.py | 2 +-
tools/arch/x86/include/asm/irq_vectors.h | 2 +-
virt/kvm/Kconfig | 6 -
virt/kvm/Makefile.kvm | 6 +-
virt/kvm/coalesced_mmio.c | 3 +-
virt/kvm/eventfd.c | 2 +-
virt/kvm/kvm_main.c | 3 +-
virt/kvm/vfio.c | 9 +-
virt/kvm/vfio.h | 2 +-
109 files changed, 489 insertions(+), 440 deletions(-)
rename include/kvm/arm_arch_timer.h => arch/arm64/include/asm/kvm_arch_timer.h (98%)
rename include/kvm/arm_pmu.h => arch/arm64/include/asm/kvm_pmu.h (99%)
rename include/kvm/arm_vgic.h => arch/arm64/include/asm/kvm_vgic.h (99%)
rename {include => arch/arm64}/kvm/arm_hypercalls.h (100%)
rename {include => arch/arm64}/kvm/arm_psci.h (100%)
rename include/{kvm/iodev.h => linux/kvm_iodev.h} (100%)

base-commit: 0bb80ecc33a8fb5a682236443c1e740d5c917d1d
--
2.42.0.459.ge4e396fd5e-goog