From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 CBA022F5A22 for ; Fri, 7 Nov 2025 01:29:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762478988; cv=none; b=VLQ5WJKST4ltNVs1wlRN2GIut2nefIYTxbQkKPwGYiG8J6ZTnRD6WHi3NQV3GeHmqiRZOrfnZDhsGg29UHirTZ35lksB91HJDpi2jojtds8D6UcC1QwKAHtmrA61hkH80NMaB0CbS5MOksGPLn+P8R6X6dm/SaiGbWM5aFXpSLY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762478988; c=relaxed/simple; bh=c8trCTn3z0/KWshOsHyPm3MhkSeG9Y5AD65+gAtTTcc=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=ToJcETb0Od3MjkxY5NRQsNWhUiUCUnH/FSQS0xHbdq/grIi0dj5zvG7Xniv2NltJAL0IH7kRmwBpELki3Rs893xMuxPQBvdjLrFlwlcuJc5J+bSzbFbtIfmnYqI9huHpN/Ubyw91D96++g3kJwkg1FYftvkPwxjtfW1Kl35ToTI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=jjT1UVn3; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="jjT1UVn3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 58562C16AAE; Fri, 7 Nov 2025 01:29:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762478988; bh=c8trCTn3z0/KWshOsHyPm3MhkSeG9Y5AD65+gAtTTcc=; h=From:To:Cc:Subject:Date:From; b=jjT1UVn3ZkxuKbtnjmNuyWFRHVAEKShZ3WMFWGK0Vb9yq3IOn5/HbYdu6bG9qPvq+ kQezKLIL2HsxyxD0j6kblXVM1Smk/LPdNYCJ49TXvuY8wV83TXczPZpmoH+ToIwpgJ swUC4dRtBJSHYcU7eX4kKL/jtBfhzylM3mCtpyTOmBBIQv/cZ9Q0oDlZB4aamZFX20 MWDqDIAKkfWYLVfzsLH0P2cGV8STrGWjy5VuFyfOP0cuPK0OtLPPjVpJSZAdykJSVz onUyACyCN3LC8jSBr6/75C9r0yYgWiIv998PYt7mAl6du3GSF4CTJJYbKiUgCUmwC+ f6Ms7nAUT5YdA== From: Oliver Upton To: kvmarm@lists.linux.dev Cc: Marc Zyngier , Joey Gouly , Suzuki K Poulose , Zenghui Yu , Oliver Upton Subject: [PATCH] KVM: arm64: vgic-v3: Reinstate IRQ lock ordering for LPI xarray Date: Thu, 6 Nov 2025 17:29:44 -0800 Message-ID: <20251107012944.1708811-1-oupton@kernel.org> X-Mailer: git-send-email 2.47.3 Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Zenghui reports that running a KVM guest with an assigned device and lockdep enabled produces an unfriendly splat due to an inconsistent irq context when taking the lpi_xa's spinlock. This is no good as in rare cases the last reference to an LPI can get dropped after injection of a cached LPI translation. In this case, vgic_put_irq() will release the IRQ struct and take the lpi_xa's spinlock to erase it from the xarray. Reinstate the IRQ ordering and update the lockdep hint accordingly. Note that there is no irqsave equivalent of might_lock(), so just explictly grab and release the spinlock on lockdep kernels. Reported-by: Zenghui Yu Closes: https://lore.kernel.org/kvmarm/b4d7cb0f-f007-0b81-46d1-998b15cc14bc@huawei.com/ Fixes: 982f31bbb5b0 ("KVM: arm64: vgic-v3: Don't require IRQs be disabled for LPI xarray lock") Signed-off-by: Oliver Upton --- arch/arm64/kvm/vgic/vgic-init.c | 2 +- arch/arm64/kvm/vgic/vgic-its.c | 7 ++++--- arch/arm64/kvm/vgic/vgic.c | 23 +++++++++++++++-------- 3 files changed, 20 insertions(+), 12 deletions(-) diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c index 1796b1a22a72..7208776ba4bf 100644 --- a/arch/arm64/kvm/vgic/vgic-init.c +++ b/arch/arm64/kvm/vgic/vgic-init.c @@ -53,7 +53,7 @@ void kvm_vgic_early_init(struct kvm *kvm) { struct vgic_dist *dist = &kvm->arch.vgic; - xa_init(&dist->lpi_xa); + xa_init_flags(&dist->lpi_xa, XA_FLAGS_LOCK_IRQ); } /* CREATION */ diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c index ce3e3ed3f29f..f162206adb48 100644 --- a/arch/arm64/kvm/vgic/vgic-its.c +++ b/arch/arm64/kvm/vgic/vgic-its.c @@ -78,6 +78,7 @@ static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid, { struct vgic_dist *dist = &kvm->arch.vgic; struct vgic_irq *irq = vgic_get_irq(kvm, intid), *oldirq; + unsigned long flags; int ret; /* In this case there is no put, since we keep the reference. */ @@ -88,7 +89,7 @@ static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid, if (!irq) return ERR_PTR(-ENOMEM); - ret = xa_reserve(&dist->lpi_xa, intid, GFP_KERNEL_ACCOUNT); + ret = xa_reserve_irq(&dist->lpi_xa, intid, GFP_KERNEL_ACCOUNT); if (ret) { kfree(irq); return ERR_PTR(ret); @@ -103,7 +104,7 @@ static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid, irq->target_vcpu = vcpu; irq->group = 1; - xa_lock(&dist->lpi_xa); + xa_lock_irqsave(&dist->lpi_xa, flags); /* * There could be a race with another vgic_add_lpi(), so we need to @@ -125,7 +126,7 @@ static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid, } out_unlock: - xa_unlock(&dist->lpi_xa); + xa_unlock_irqrestore(&dist->lpi_xa, flags); if (ret) return ERR_PTR(ret); diff --git a/arch/arm64/kvm/vgic/vgic.c b/arch/arm64/kvm/vgic/vgic.c index 6dd5a10081e2..8d20c53faef0 100644 --- a/arch/arm64/kvm/vgic/vgic.c +++ b/arch/arm64/kvm/vgic/vgic.c @@ -28,7 +28,7 @@ struct vgic_global kvm_vgic_global_state __ro_after_init = { * kvm->arch.config_lock (mutex) * its->cmd_lock (mutex) * its->its_lock (mutex) - * vgic_dist->lpi_xa.xa_lock + * vgic_dist->lpi_xa.xa_lock must be taken with IRQs disabled * vgic_cpu->ap_list_lock must be taken with IRQs disabled * vgic_irq->irq_lock must be taken with IRQs disabled * @@ -141,32 +141,39 @@ static __must_check bool vgic_put_irq_norelease(struct kvm *kvm, struct vgic_irq void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq) { struct vgic_dist *dist = &kvm->arch.vgic; + unsigned long flags; - if (irq->intid >= VGIC_MIN_LPI) - might_lock(&dist->lpi_xa.xa_lock); + /* + * Normally the lock is only taken when the refcount drops to 0. + * Acquire/release it early on lockdep kernels to make locking issues + * in rare release paths a bit more obvious. + */ + if (IS_ENABLED(CONFIG_LOCKDEP) && irq->intid >= VGIC_MIN_LPI) { + guard(spinlock_irqsave)(&dist->lpi_xa.xa_lock); + } if (!__vgic_put_irq(kvm, irq)) return; - xa_lock(&dist->lpi_xa); + xa_lock_irqsave(&dist->lpi_xa, flags); vgic_release_lpi_locked(dist, irq); - xa_unlock(&dist->lpi_xa); + xa_unlock_irqrestore(&dist->lpi_xa, flags); } static void vgic_release_deleted_lpis(struct kvm *kvm) { struct vgic_dist *dist = &kvm->arch.vgic; - unsigned long intid; + unsigned long flags, intid; struct vgic_irq *irq; - xa_lock(&dist->lpi_xa); + xa_lock_irqsave(&dist->lpi_xa, flags); xa_for_each(&dist->lpi_xa, intid, irq) { if (irq->pending_release) vgic_release_lpi_locked(dist, irq); } - xa_unlock(&dist->lpi_xa); + xa_unlock_irqrestore(&dist->lpi_xa, flags); } void vgic_flush_pending_lpis(struct kvm_vcpu *vcpu) base-commit: 6146a0f1dfae5d37442a9ddcba012add260bceb0 -- 2.47.3