From patchwork Wed Jan 24 20:49:02 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Oliver Upton X-Patchwork-Id: 13529658 Received: from out-172.mta1.migadu.com (out-172.mta1.migadu.com [95.215.58.172]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6ADCC1350E8 for ; Wed, 24 Jan 2024 20:49:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706129381; cv=none; b=m4RigZE1KmxXUZ95yc68vQxD58L6DSK0Tafn7WiQOiefzyJ2s7F8qa+/bL0e8I5pAf4nbRV32uhsg0igaG5C+9OkZoX6AXaskD/G5jAU065nbY9lNGuhyatx1WbIX4f0i+fEI/QuDhxm6Y/lhwxC9F4zGvhY2UXw3trPxg40L7Q= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706129381; c=relaxed/simple; bh=DAkL2Y9gxAm/I7me//FA38b8lKO9PwoCRKLKU4/roWc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=eyE5DH+YIn7DSn4au5tJfslNGOxWd8An3s0Gg9EdfagTMGwH9VGu2+a9zvumzE50fWL4jieV/eHv0kc+HbiWOpPVOMaSj04fclmEM68RbVLx1SaVlRCvHQ1sMcVXmD7+KuoevbqWc4x2kVOzUQ2s1nsjrDZdXR6QO/k+NjDVy3U= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=SqbU3ANK; arc=none smtp.client-ip=95.215.58.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="SqbU3ANK" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1706129376; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=t+qjGFCXzXN4Bwc8iaYXwhCvz8/RNxUojqqBTdUJ0KM=; b=SqbU3ANKSAqHlEzCx0w6jK0PtznQH31HZOLK8yjb43D0hZl042x2NxiiTABADbuelBSBCv EW3i/orakJzSy5v1io8w5tQ+XghZRna9t02DIuJ8caJDLUbylgSUrD4voVXCBMdxBm8dBA pmlNRtkmpdXaHvrR99MoTP10smAyWZA= From: Oliver Upton To: kvmarm@lists.linux.dev Cc: kvm@vger.kernel.org, Marc Zyngier , James Morse , Suzuki K Poulose , Zenghui Yu , Raghavendra Rao Ananta , Jing Zhang , Oliver Upton Subject: [PATCH 08/15] KVM: arm64: vgic: Rely on RCU protection in vgic_get_lpi() Date: Wed, 24 Jan 2024 20:49:02 +0000 Message-ID: <20240124204909.105952-9-oliver.upton@linux.dev> In-Reply-To: <20240124204909.105952-1-oliver.upton@linux.dev> References: <20240124204909.105952-1-oliver.upton@linux.dev> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT Stop acquiring the lpi_list_lock in favor of RCU for protecting the read-side critical section in vgic_get_lpi(). In order for this to be safe, we also need to be careful not to take a reference on an irq with a refcount of 0, as it is about to be freed. Signed-off-by: Oliver Upton --- arch/arm64/kvm/vgic/vgic.c | 9 ++++----- arch/arm64/kvm/vgic/vgic.h | 11 ++++++++--- 2 files changed, 12 insertions(+), 8 deletions(-) diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c index be3ed4c5e1fa..949af87bb599 100644 --- a/arch/arm64/kvm/vgic/vgic.c +++ b/arch/arm64/kvm/vgic/vgic.c @@ -62,15 +62,14 @@ static struct vgic_irq *vgic_get_lpi(struct kvm *kvm, u32 intid) { struct vgic_dist *dist = &kvm->arch.vgic; struct vgic_irq *irq = NULL; - unsigned long flags; - raw_spin_lock_irqsave(&dist->lpi_list_lock, flags); + rcu_read_lock(); irq = xa_load(&dist->lpi_xa, intid); - if (irq) - vgic_get_irq_kref(irq); + if (irq && !vgic_try_get_irq_kref(irq)) + irq = NULL; - raw_spin_unlock_irqrestore(&dist->lpi_list_lock, flags); + rcu_read_unlock(); return irq; } diff --git a/arch/arm64/kvm/vgic/vgic.h b/arch/arm64/kvm/vgic/vgic.h index 8d134569d0a1..20886f57416a 100644 --- a/arch/arm64/kvm/vgic/vgic.h +++ b/arch/arm64/kvm/vgic/vgic.h @@ -220,12 +220,17 @@ void vgic_v2_vmcr_sync(struct kvm_vcpu *vcpu); void vgic_v2_save_state(struct kvm_vcpu *vcpu); void vgic_v2_restore_state(struct kvm_vcpu *vcpu); -static inline void vgic_get_irq_kref(struct vgic_irq *irq) +static inline bool vgic_try_get_irq_kref(struct vgic_irq *irq) { if (irq->intid < VGIC_MIN_LPI) - return; + return true; + + return kref_get_unless_zero(&irq->refcount); +} - kref_get(&irq->refcount); +static inline void vgic_get_irq_kref(struct vgic_irq *irq) +{ + WARN_ON_ONCE(!vgic_try_get_irq_kref(irq)); } void vgic_v3_fold_lr_state(struct kvm_vcpu *vcpu);