This was _supposed_ to be a tiny one-off patch to fix a nVMX bug where KVM
fails to detect that, after nested VM-Exit, L1 has a pending IRQ (or NMI).
But because x86's nested teardown flows are garbage (KVM simply forces a
nested VM-Exit to put the vCPU back into L1), that simple fix snowballed.
The immediate issue is that checking for a pending interrupt accesses the
legacy PIC, and x86's kvm_arch_destroy_vm() currently frees the PIC before
destroying vCPUs, i.e. checking for IRQs during the forced nested VM-Exit
results in a NULL pointer deref (or use-after-free if KVM didn't nullify
the PIC pointer). That's patch 1.
Patch 2 is the original nVMX fix.
The remaining patches attempt to bring a bit of sanity to x86's VM
teardown code, which has accumulated a lot of cruft over the years. E.g.
KVM currently unloads each vCPU's MMUs in a separate operation from
destroying vCPUs, all because when guest SMP support was added, KVM had a
kludgy MMU teardown flow that broken when a VM had more than one 1 vCPU.
And that oddity lived on, for 18 years...
Sean Christopherson (7):
KVM: x86: Free vCPUs before freeing VM state
KVM: nVMX: Process events on nested VM-Exit if injectable IRQ or NMI
is pending
KVM: Assert that a destroyed/freed vCPU is no longer visible
KVM: x86: Don't load/put vCPU when unloading its MMU during teardown
KVM: x86: Unload MMUs during vCPU destruction, not before
KVM: x86: Fold guts of kvm_arch_sync_events() into
kvm_arch_pre_destroy_vm()
KVM: Drop kvm_arch_sync_events() now that all implementations are nops
arch/arm64/include/asm/kvm_host.h | 2 --
arch/loongarch/include/asm/kvm_host.h | 1 -
arch/mips/include/asm/kvm_host.h | 1 -
arch/powerpc/include/asm/kvm_host.h | 1 -
arch/riscv/include/asm/kvm_host.h | 2 --
arch/s390/include/asm/kvm_host.h | 1 -
arch/x86/kvm/vmx/nested.c | 11 +++++++
arch/x86/kvm/x86.c | 42 ++++++++++-----------------
include/linux/kvm_host.h | 1 -
virt/kvm/kvm_main.c | 9 +++++-
10 files changed, 34 insertions(+), 37 deletions(-)
base-commit: fed48e2967f402f561d80075a20c5c9e16866e53
--
2.48.1.658.g4767266eb4-goog
