Re: [PATCH v2 1/7] KVM: arm64: Move OUTSIDE_GUEST_MODE publication past context being saved
flat view
From: Fuad Tabba <fuad.tabba@linux.dev>
Date: 2026-09-29 13:00:03
Also in:
kvmarm, stable
Hi Marc, On Tue, 29 Sep 2026 10:35:42 +0100, Marc Zyngier [off-list ref] wrote: [...]
Move the publication of OUTSIDE_GUEST_MODE to the point where the state is actually written, and give this write release semantics to ensure the correct ordering. Signed-off-by: Marc Zyngier <maz@kernel.org> Cc: stable@vger.kernel.org
No Fixes: tag? [...]
quoted hunk ↗ jump to hunk
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
[...]
quoted hunk ↗ jump to hunk
@@ -1386,6 +1385,12 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu) kvm_arch_vcpu_ctxsync_fp(vcpu); + /* + * All the state has been synchronised, let advertise + * we're outside of the guest. + */ + smp_store_release(&vcpu->mode, OUTSIDE_GUEST_MODE);
Pardon my atomics :), but what does the release pair with? On the halt path, the only reader I can find is the cmpxchg() in kvm_vcpu_exiting_guest_mode(), and the LPI-disable and MOVALL halts then take ap_list_lock or irq_lock. Would WRITE_ONCE() be enough? Should the early exit path (the kvm_vcpu_exit_request() bail-out) get the same treatment? I think that's what Sashiko is trying to say in the patch 5 review [1]. nit: "let advertise" -> "publish"? Cheers, /fuad [1] https://sashiko.dev/#/patchset/20260929093548.3598547-1-maz%40kernel.org?part=5