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* [PATCH 0/7] KVM: Ensure WAIT requests actually wait
@ 2026-10-28 19:02 Sean Christopherson
  2026-10-28 19:02 ` [PATCH 1/7] KVM: s390: Drop unused and unreachable kvm_arch_vcpu_should_kick() Sean Christopherson
                   ` (6 more replies)
  0 siblings, 7 replies; 8+ messages in thread
From: Sean Christopherson @ 2026-10-28 19:02 UTC (permalink / raw)
  To: Marc Zyngier, Oliver Upton, Tianrui Zhao, Bibo Mao, Huacai Chen,
	Madhavan Srinivasan, Anup Patel, Paul Walmsley, Palmer Dabbelt,
	Albert Ou, Sean Christopherson, Paolo Bonzini
  Cc: Fuad Tabba, Joey Gouly, Steffen Eiden, Suzuki K Poulose,
	Zenghui Yu, Nicholas Piggin, Atish Patra, Alexandre Ghiti,
	linux-arm-kernel, kvmarm, kvm, loongarch, linux-mips,
	linuxppc-dev, kvm-riscv, linux-riscv, linux-kernel,
	Stefan Teodorescu

Fix a bug in where kvm_make_request_and_kick() won't actually wait if the
kick races without another non-waiting kick.  The issue is that all of the
conditional kvm_arch_vcpu_should_kick() implementations are missing this code:

	if (req & KVM_REQUEST_WAIT)
		return mode != OUTSIDE_GUEST_MODE;

Thankfully, kvm_request_needs_ipi() does the right thing, so this doesn't
affect kvm_make_all_cpus_request() or kvm_make_vcpus_request_mask(), i.e. it's
limited to x86 SNP's used of kvm_make_request_and_kick().

To fix, address this TODO:

  /* TODO: merge with kvm_arch_vcpu_should_kick */

and purge kvm_arch_vcpu_should_kick().  As usual, PPC makes that difficult
because it has wonky code that is poorly documented.  For reasons unknown,
kvm_vcpu_kick() unconditionally returns true on (most flavors of) PPC.  To
preserve that behavior, add a compatibility wrapper in PPC, along with a
@force param to __kvm_vcpu_kick().

This series would ideally go into 7.4, even though it's obviously not small,
as guest_memfd in-place conversion massively widens the window where a missed
kick+wait can lead to the host trying to reclaim an in-use VMSA page, which
is generally fatal to the host.

Sean Christopherson (7):
  KVM: s390: Drop unused and unreachable kvm_arch_vcpu_should_kick()
  KVM: Add a @force param to __kvm_vcpu_kick() for PPC backwards
    compatibility
  KVM: PPC: Explicitly force IPIs when directly kicking vCPUs
  KVM: MIPS: Rework kvm_arch_vcpu_should_kick() to use standard
    implementation
  KVM: Move kvm_arch_vcpu_should_kick() to common code as
    kvm_vcpu_should_kick()
  KVM: Plumb the full request into __kvm_vcpu_kick()
  KVM: Drop kvm_vcpu_should_kick() and use kvm_request_needs_ipi()

 arch/arm64/kvm/arm.c               |  5 -----
 arch/loongarch/kvm/vcpu.c          |  5 -----
 arch/mips/kvm/mips.c               |  5 -----
 arch/powerpc/include/asm/kvm_ppc.h | 13 ++++++++++++-
 arch/powerpc/kvm/book3s.c          |  4 ++--
 arch/powerpc/kvm/book3s_pr.c       |  2 +-
 arch/powerpc/kvm/booke.c           |  6 +++---
 arch/powerpc/kvm/e500_emulate.c    |  2 +-
 arch/powerpc/kvm/powerpc.c         |  7 +------
 arch/riscv/kvm/vcpu.c              |  5 -----
 arch/s390/kvm/s390/s390.c          |  7 -------
 arch/x86/kvm/x86.c                 |  5 -----
 include/linux/kvm_host.h           |  7 +++----
 virt/kvm/kvm_main.c                | 28 ++++++++++++++++------------
 14 files changed, 39 insertions(+), 62 deletions(-)


base-commit: 7e60162b16f9da0d2fa83da5c1723b6853a0ac1d
-- 
2.56.0.313.g2479322e68-goog



^ permalink raw reply	[flat|nested] 8+ messages in thread
end of thread, other threads:[~2026-10-28 19:03 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-10-28 19:02 [PATCH 0/7] KVM: Ensure WAIT requests actually wait Sean Christopherson
2026-10-28 19:02 ` [PATCH 1/7] KVM: s390: Drop unused and unreachable kvm_arch_vcpu_should_kick() Sean Christopherson
2026-10-28 19:02 ` [PATCH 2/7] KVM: Add a @force param to __kvm_vcpu_kick() for PPC backwards compatibility Sean Christopherson
2026-10-28 19:02 ` [PATCH 3/7] KVM: PPC: Explicitly force IPIs when directly kicking vCPUs Sean Christopherson
2026-10-28 19:02 ` [PATCH 4/7] KVM: MIPS: Rework kvm_arch_vcpu_should_kick() to use standard implementation Sean Christopherson
2026-10-28 19:02 ` [PATCH 5/7] KVM: Move kvm_arch_vcpu_should_kick() to common code as kvm_vcpu_should_kick() Sean Christopherson
2026-10-28 19:02 ` [PATCH 6/7] KVM: Plumb the full request into __kvm_vcpu_kick() Sean Christopherson
2026-10-28 19:02 ` [PATCH 7/7] KVM: Drop kvm_vcpu_should_kick() and use kvm_request_needs_ipi() Sean Christopherson

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