linux-kernel - Re: [GIT PULL] KVM: Generic changes for 6.20

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Message-ID: <CABgObfZeV6D-2cEht1300xNgxYtz=mi6oX4-D8x7exittEe22Q@mail.gmail.com>
Date: Mon, 9 Feb 2026 18:38:11 +0100
From: Paolo Bonzini <pbonzini@...hat.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL] KVM: Generic changes for 6.20

On Sat, Feb 7, 2026 at 5:10 AM Sean Christopherson <seanjc@...gle.com> wrote:
>  - Document that vcpu->mutex is take outside of kvm->slots_lock, which is all
>    kinds of unintuitive, but is unfortunately the existing behavior for
>    multiple architectures, and in a weird way actually makes sense.

I disagree that it is "arguably wrong" how you put it in the commit
message. vcpu->mutex is really a "don't worry about multiple ioctls at
the same time" mutex that tries to stay out of the way.  It only
becomes unintuitive in special cases like
tdx_acquire_vm_state_locks().

By itself this would not be a reason to resend, but while at it you
could mention that vcpu->mutex is taken outside kvm->slots_arch_lock?

Paolo

> ----------------------------------------------------------------
> Sean Christopherson (2):
>       KVM: Remove subtle "struct kvm_stats_desc" pseudo-overlay
>       Documentation: KVM: Formalizing taking vcpu->mutex *outside* of kvm->slots_lock
>
>  Documentation/virt/kvm/locking.rst |  2 +
>  arch/arm64/kvm/guest.c             |  4 +-
>  arch/loongarch/kvm/vcpu.c          |  2 +-
>  arch/loongarch/kvm/vm.c            |  2 +-
>  arch/mips/kvm/mips.c               |  4 +-
>  arch/powerpc/kvm/book3s.c          |  4 +-
>  arch/powerpc/kvm/booke.c           |  4 +-
>  arch/riscv/kvm/vcpu.c              |  2 +-
>  arch/riscv/kvm/vm.c                |  2 +-
>  arch/s390/kvm/kvm-s390.c           |  4 +-
>  arch/x86/kvm/x86.c                 |  4 +-
>  include/linux/kvm_host.h           | 83 ++++++++++++++++----------------------
>  include/uapi/linux/kvm.h           |  8 ++++
>  virt/kvm/binary_stats.c            |  2 +-
>  virt/kvm/kvm_main.c                | 20 ++++-----
>  15 files changed, 72 insertions(+), 75 deletions(-)
>