From: Sean Christopherson <seanjc@google.com>
To: Jim Mattson <jmattson@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
David Woodhouse <dwmw2@infradead.org>,
Paul Durrant <paul@xen.org>, Gleb Natapov <gleb@redhat.com>,
Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
Suzuki Poulose <suzuki@in.ibm.com>,
Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
Jan Kiszka <jan.kiszka@siemens.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] KVM: x86: Clear pv_unhalted on all transitions to KVM_MP_STATE_RUNNABLE
Date: Wed, 12 Feb 2025 08:49:22 -0800 [thread overview]
Message-ID: <Z6zREu-pShh-ivK-@google.com> (raw)
In-Reply-To: <CALMp9eRB025OAi2fpdweKr+fOAovmOKfF7XPwvf8HJKbJSvmhg@mail.gmail.com>
On Wed, Feb 05, 2025, Jim Mattson wrote:
> On Mon, Jan 13, 2025 at 12:02 PM Jim Mattson <jmattson@google.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.
I'll add it to the list, and drop the "list may be incomplete" line.
KVM_HC_KICK_CPU is unreachable if Xen hypercalls are enabled, but nothing would
prevent a clever guest from sending an virtual IPI with APIC_DM_REMRD. Whether
or not that makes the Xen code a KVM bug is definitely debatable, but I can't
imagine will care about Fixes being slightly overzealous.
next prev parent reply other threads:[~2025-02-12 16:49 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-01-13 20:01 [PATCH 0/2] KVM: x86: Clean up MP_STATE transitions Jim Mattson
2025-01-13 20:01 ` [PATCH 1/2] KVM: x86: Introduce kvm_set_mp_state() Jim Mattson
2025-02-12 16:42 ` Sean Christopherson
2025-01-13 20:01 ` [PATCH 2/2] KVM: x86: Clear pv_unhalted on all transitions to KVM_MP_STATE_RUNNABLE Jim Mattson
2025-02-05 18:45 ` Jim Mattson
2025-02-12 16:49 ` Sean Christopherson [this message]
2025-02-15 0:50 ` [PATCH 0/2] KVM: x86: Clean up MP_STATE transitions Sean Christopherson
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