linux-kernel - Re: [PATCH 2/2] KVM: x86: Clear pv_unhalted on all transitions to KVM_MP_STATE

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Message-ID: <CALMp9eRB025OAi2fpdweKr+fOAovmOKfF7XPwvf8HJKbJSvmhg@mail.gmail.com>
Date: Wed, 5 Feb 2025 10:45:08 -0800
From: Jim Mattson <jmattson@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>, 
	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"H . Peter Anvin" <hpa@...or.com>, David Woodhouse <dwmw2@...radead.org>, Paul Durrant <paul@....org>, 
	Gleb Natapov <gleb@...hat.com>, Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>, 
	Suzuki Poulose <suzuki@...ibm.com>, Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>, 
	Jan Kiszka <jan.kiszka@...mens.com>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] KVM: x86: Clear pv_unhalted on all transitions to KVM_MP_STATE_RUNNABLE

On Mon, Jan 13, 2025 at 12:02 PM Jim Mattson <jmattson@...gle.com> wrote:
>
> In kvm_set_mp_state(), ensure that vcpu->arch.pv.pv_unhalted is always
> cleared on a transition to KVM_MP_STATE_RUNNABLE, so that the next HLT
> instruction will be respected.
>
> The "fixes" list may be incomplete.

The only commit I'm not sure of is commit 1a65105a5aba ("KVM: x86/xen:
handle PV spinlocks slowpath"). That commit introduces an mp_state
transition to KVM_MP_STATE_RUNNABLE  without clearing pv_unhalted, so
perhaps it should be in the "fixes" list. OTOH, this seems to be an
independent implementation of PV spinlocks, so maybe it's not a
problem.

> Fixes: 6aef266c6e17 ("kvm hypervisor : Add a hypercall to KVM hypervisor to support pv-ticketlocks")
> Fixes: b6b8a1451fc4 ("KVM: nVMX: Rework interception of IRQs and NMIs")
> Fixes: 38c0b192bd6d ("KVM: SVM: leave halted state on vmexit")
> Signed-off-by: Jim Mattson <jmattson@...gle.com>