linux-kernel - [PATCH 0/7] KVM: x86: nVMX IRQ fix and VM teardown cleanups

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Message-ID: <20250224235542.2562848-1-seanjc@google.com>
Date: Mon, 24 Feb 2025 15:55:35 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>, 
	Tianrui Zhao <zhaotianrui@...ngson.cn>, Bibo Mao <maobibo@...ngson.cn>, 
	Huacai Chen <chenhuacai@...nel.org>, Madhavan Srinivasan <maddy@...ux.ibm.com>, 
	Anup Patel <anup@...infault.org>, Paul Walmsley <paul.walmsley@...ive.com>, 
	Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
	Christian Borntraeger <borntraeger@...ux.ibm.com>, Janosch Frank <frankja@...ux.ibm.com>, 
	Claudio Imbrenda <imbrenda@...ux.ibm.com>, Sean Christopherson <seanjc@...gle.com>, 
	Paolo Bonzini <pbonzini@...hat.com>
Cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
	kvm@...r.kernel.org, loongarch@...ts.linux.dev, linux-mips@...r.kernel.org, 
	linuxppc-dev@...ts.ozlabs.org, kvm-riscv@...ts.infradead.org, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	Aaron Lewis <aaronlewis@...gle.com>, Jim Mattson <jmattson@...gle.com>, 
	Yan Zhao <yan.y.zhao@...el.com>, Rick P Edgecombe <rick.p.edgecombe@...el.com>, 
	Kai Huang <kai.huang@...el.com>, Isaku Yamahata <isaku.yamahata@...el.com>
Subject: [PATCH 0/7] KVM: x86: nVMX IRQ fix and VM teardown cleanups

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