From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 06E76435523 for ; Wed, 26 Aug 2026 17:37:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787765866; cv=none; b=E6UYgLUTXlWU++79IcDRBhNMNZcqESS3NYKpQH8Xa2nS9sw8f3gW5pkDPrY0MKixN+az2qPpIAAtDhzHakEDu2+/FNDUaKqByW06PzFrqKKZIOToQKqUl0TTwHYY1y0I3zvK/sZYGdnow026GwQkZGW2kAo34ZhWuzuAg0622G8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787765866; c=relaxed/simple; bh=J56Od10YjLBfXjaRtkbFgU50yw7N6bEFMogt4hSy9o4=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=QbqvleU36o/7td28C5h/fnu+fTKsHSddu6Cc1FK5Nra+d5BLVEEDMTBNUdvzDrKsascwu+23bDJC9lQp6yarRvzrNayamnv1eeLp6q1PonpR3ibknhZbJ+wCtkxjr98op9irXYND98eN7+VqOQVrsbSR1f26XRErIo1jr2hzSKk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=ctt9Emt8; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ctt9Emt8" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1787765854; 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; bh=f7NGWrMVOmUns/2V3+RO3qremiV9F2t/yCezPuNANs4=; b=ctt9Emt8O+0kkpxfetW2NekYvpi513xoGV0zSglcDhT0fpLVTm1wo0bC5Nj4IB8nZ0H3w8 edrusM5Avik70V9Kt/BRefF+JQcKtWJWVX3Rgdelbny4bypJWKD/Yb0YPXSpT654HCnKHt LMHnBRlTNvxe1/tnLiUf83ay1CbjzG0= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-522-wV5FI6iTPKWlzZKe162mDw-1; Wed, 26 Aug 2026 13:37:28 -0400 X-MC-Unique: wV5FI6iTPKWlzZKe162mDw-1 X-Mimecast-MFC-AGG-ID: wV5FI6iTPKWlzZKe162mDw_1787765846 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 296B91862D5C; Wed, 26 Aug 2026 17:37:26 +0000 (UTC) Received: from llong-thinkpadp16vgen1.rmtusnh.csb (headnet05.pony-001.prod.iad2.dc.redhat.com [10.2.32.117]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 1CB5E1800598; Wed, 26 Aug 2026 17:37:23 +0000 (UTC) From: Waiman Long To: "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Long Li , Saurabh Sengar , Michael Kelley Cc: linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, Waiman Long Subject: [PATCH] Drivers: hv: Avoid infinite retry loop in init_vp_index() Date: Wed, 26 Aug 2026 13:37:10 -0400 Message-ID: <20260826173710.511604-1-longman@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 There is a retry loop in init_vp_index() where the CPUs from a certain node are stripped out if they have already been in the allocated cpumask or not in HK_TYPE_MANAGED_IRQ housekeeping cpumask. If there is no CPU left, the allocated cpumask is ignored and the process is retried again. However, if the HK_TYPE_MANAGED_IRQ housekeeping cpumask turns out not to contain any CPU in that particular node, that will become an infinite retry loop. This particular problem was reported by sashiko [1]. This should rarely happen, but we still need to guard against this. Fix this infinite loop problem by ignoring the HK_TYPE_MANAGED_IRQ housekeeping cpumask if the allocated cpumask has already been cleared before. Since the HK_TYPE_MANAGED_IRQ housekeeping cpumask is supposed to be used on a best effort basis, it is OK to ignore it in this particular case. Also add a check_hkcpu boolean flag in struct vmbus_channel to control the HK_TYPE_MANAGED_IRQ housekeeping CPU check in target_cpu_store() and init_vp_index(). Link: https://sashiko.dev/#/message/20260422030903.E1BFCC2BCB0%40smtp.kernel.org [1] Fixes: 6640b5df1a38 ("Drivers: hv: vmbus: Don't assign VMbus channel interrupts to isolated CPUs") Signed-off-by: Waiman Long --- drivers/hv/channel_mgmt.c | 14 +++++++++++--- drivers/hv/vmbus_drv.c | 3 ++- include/linux/hyperv.h | 7 +++++++ 3 files changed, 20 insertions(+), 4 deletions(-) diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c index 89d214dda360..30d91668e1c5 100644 --- a/drivers/hv/channel_mgmt.c +++ b/drivers/hv/channel_mgmt.c @@ -774,6 +774,7 @@ static void init_vp_index(struct vmbus_channel *channel) } for (i = 1; i <= ncpu + 1; i++) { + channel->check_hkcpu = true; while (true) { numa_node = next_numa_node_id++; if (numa_node == nr_node_ids) { @@ -788,14 +789,21 @@ static void init_vp_index(struct vmbus_channel *channel) retry: cpumask_xor(available_mask, allocated_mask, cpumask_of_node(numa_node)); - cpumask_and(available_mask, available_mask, hk_mask); + if (channel->check_hkcpu) + cpumask_and(available_mask, available_mask, hk_mask); if (cpumask_empty(available_mask)) { /* * We have cycled through all the CPUs in the node; - * reset the allocated map. + * reset the allocated map. If the allocated map has + * already been cleared, we will have to ignore the + * HK_TYPE_MANAGED_IRQ housekeeping cpumask as its use + * is on a best effort basis, not a must. */ - cpumask_clear(allocated_mask); + if (!cpumask_empty(allocated_mask)) + cpumask_clear(allocated_mask); + else + channel->check_hkcpu = false; goto retry; } diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index 6824bd7cb3c4..bea578cd0aa7 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -1751,7 +1751,8 @@ int vmbus_channel_set_cpu(struct vmbus_channel *channel, u32 target_cpu) if (target_cpu >= nr_cpumask_bits) return -EINVAL; - if (!cpumask_test_cpu(target_cpu, housekeeping_cpumask(HK_TYPE_MANAGED_IRQ))) + if (channel->check_hkcpu && + !cpumask_test_cpu(target_cpu, housekeeping_cpumask(HK_TYPE_MANAGED_IRQ))) return -EINVAL; if (!cpu_online(target_cpu)) diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h index a2b484679eb4..0d8df79c26ca 100644 --- a/include/linux/hyperv.h +++ b/include/linux/hyperv.h @@ -831,6 +831,13 @@ struct vmbus_channel { */ bool out_full_flag; + /* + * Check target_cpu in target_cpu_store() to make sure that it is in the + * HK_TYPE_MANAGED_IRQ housekeeping cpumask and reject it if not when + * the flag is set. + */ + bool check_hkcpu; + /* Channel callback's invoked in softirq context */ struct tasklet_struct callback_event; void (*onchannel_callback)(void *context); -- 2.55.0