From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 7FCE0478E53 for ; Tue, 14 Jul 2026 13:06:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784034388; cv=none; b=eOJbpurtp/Yrf8upNYckSO3eazPIxc1REh7VYofGO5lXG9DSkqedyNPzkRFf4JK6qP17VbetqBne+mXmBNfAu5Lt8M9hQfWF1dLkbje/zum1MxhfdLPhzCYXHNLML3uiY4nBOnjWgZ2cPXXcojiZt+J/ToX6NBoCGE35r+JGV4A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784034388; c=relaxed/simple; bh=71fgk7/pjKbIL3/bv557fkIpwYnWwWChravaY+wLfFg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=JLrvvGZHNDK2WjKPdjMNFO39KYvi+MZc4bGQRbAUpUbRdyzq5QRxekVsDc+4uB8SjzXqMqILCgCQASO5P1Vx4+EBYE+cQdQJfikI1BJUGq9bK2blzDZCtnSPHh5+jnND2aQRGqVdDJfJzUN+2Pcxsn3ZPR6U+9C1ygV8xQv7G4I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XwyYkiEo; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="XwyYkiEo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2C10D1F00AC4; Tue, 14 Jul 2026 13:06:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784034387; bh=n5uZic2yQEf6J+MPzYVAL97zNM1jCY/8xBbV5VkLom0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=XwyYkiEoqtwMmiD4xVL+MBmHsJCedGnMjYjtF7ZQ2NLepWSeWorhUpxLfvE/DFku0 +u3EAX8QG/xj9D79OwLnv8xgPquStq1bk0cMgkhwzpV/AlRtLyaHxTZETFvRpDOm+4 O88eKBCgFzRf4rwO4X6bT9pTudZEI9WDJOXd3ZaZeoZbsCpCH9R3aUGTjqvdtSExIm zv8FOfz7QH8Q91sBi96FI/BCUFv9qYnkcKbQ+yhrTwwZ3+kKLjnKmwDsQ8CxYIILRH iPx6zwiqznikPOtZohxKfLMaPiNMDSI5Mc7Syj0ixv5XpCr4vZJOI+E9u9HK5tXd2C 9hqISmIpo4bLg== From: Simon Horman To: mmc@linux.ibm.com Cc: Simon Horman , netdev@vger.kernel.org, bjking1@linux.ibm.com, haren@linux.ibm.com, ricklind@linux.ibm.com, kuba@kernel.org, edumazet@google.com, pabeni@redhat.com, linuxppc-dev@lists.ozlabs.org, maddy@linux.ibm.com, mpe@ellerman.id.au, davemarq@linux.ibm.com Subject: Re: [PATCH net-next v3 13/15] ibmveth: Implement incremental MQ RX queue resize Date: Tue, 14 Jul 2026 14:03:46 +0100 Message-ID: <20260714130344.1841551-3-horms@kernel.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260706193603.8039-14-mmc@linux.ibm.com> References: <20260706193603.8039-14-mmc@linux.ibm.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit This is an AI-generated review of your patch. The human sending this email has considered the AI review valid, or at least plausible. Full review at: https://sashiko.dev --- Date: Mon Jul 6 19:36:01 2026 +0000 ibmveth: Implement incremental MQ RX queue resize Add helpers to register/deregister individual RX queues and scale queue count up or down while the netdev stays up. Surviving queues keep PHYP handles, buffer pools, and IRQ state across resize. > diff --git a/drivers/net/ethernet/ibm/ibmveth.c b/drivers/net/ethernet/ibm/ibmveth.c > index ecc472ee8f71f..ac4d89a66a8db 100644 > --- a/drivers/net/ethernet/ibm/ibmveth.c > +++ b/drivers/net/ethernet/ibm/ibmveth.c [ ... ] > @@ -1080,6 +1132,138 @@ static void ibmveth_free_buffer_pools(struct ibmveth_adapter *adapter) > +static int > +ibmveth_alloc_single_rx_queue(struct ibmveth_adapter *adapter, int queue_idx, > + int rxq_entries) > +{ [ ... ] > + for (i = 0; i < IBMVETH_NUM_BUFF_POOLS; i++) { > + adapter->rx_buff_pool[queue_idx][i].size = > + adapter->rx_buff_pool[0][i].size; > + adapter->rx_buff_pool[queue_idx][i].buff_size = > + adapter->rx_buff_pool[0][i].buff_size; > + adapter->rx_buff_pool[queue_idx][i].threshold = > + adapter->rx_buff_pool[0][i].threshold; > + adapter->rx_buff_pool[queue_idx][i].active = > + adapter->rx_buff_pool[0][i].active; > + } [Severity: Critical] Does this loop miss initializing pool->index? If pool->index remains 0 for all buffer pools on the new queue, when replenishing, 0 is shifted into the correlator. Then when receiving, ibmveth_remove_buffer_from_pool() will extract pool=0, which fetches from the wrong pool and could corrupt the free map of pool 0, leading to a use-after-free or leak. [ ... ] > @@ -1192,6 +1376,49 @@ static int ibmveth_rxq_harvest_buffer(struct ibmveth_adapter *adapter, > +static int > +ibmveth_drain_rx_queue(struct ibmveth_adapter *adapter, int queue_index) > +{ [ ... ] > + while (drained < limit && > + ibmveth_rxq_pending_buffer(adapter, queue_index)) { > + rc = ibmveth_rxq_harvest_buffer(adapter, queue_index, true); Simon says: I think we can consider the issue below in the context of possible follow-up, because I believe the use of this pattern predates this patch. [Severity: High] Is a read memory barrier needed between reading the toggle bit in ibmveth_rxq_pending_buffer() and reading the correlator in ibmveth_rxq_harvest_buffer()? Since the hypervisor could be actively writing new descriptors while this is called, could a weakly-ordered CPU reorder the correlator load before the toggle bit load, causing us to recycle the wrong buffer? [ ... ] > @@ -1491,6 +1718,175 @@ ibmveth_deregister_single_rx_queue(struct ibmveth_adapter *adapter, > +static int > +ibmveth_resize_rx_queues_incremental(struct ibmveth_adapter *adapter, > + int new_count, int rxq_entries) > +{ [ ... ] > + rc = ibmveth_enable_irq(adapter, i); > + if (rc) { > + netdev_err(netdev, > + "Failed to enable IRQ for queue %d: %d\n", > + i, rc); > + ibmveth_cleanup_single_rx_interrupt(adapter, i); > + ibmveth_deregister_single_rx_queue(adapter, i); > + ibmveth_free_single_rx_queue(adapter, i); > + goto cleanup_new_queues; > + } > + > + napi_enable(&adapter->napi[i]); > + } > + > + adapter->num_rx_queues = new_count; [Severity: High] What happens if an interrupt fires on the newly added queue before adapter->num_rx_queues is updated? If an interrupt fires between ibmveth_enable_irq() and the update of adapter->num_rx_queues, ibmveth_interrupt() might evaluate: WARN_ON(qindex < 0 || qindex >= adapter->num_rx_queues) to true and return IRQ_NONE without masking the interrupt. Could this lead to an unhandled interrupt storm? [ ... ] > + } else { > + netdev_dbg(netdev, "Scale-down: removing queues %d-%d\n", > + new_count, old_count - 1); > + > + for (i = new_count; i < old_count; i++) > + napi_disable(&adapter->napi[i]); > + > + for (i = new_count; i < old_count; i++) > + ibmveth_drain_rx_queue(adapter, i); > + > + synchronize_net(); [Severity: High] Can disabling NAPI before disabling the hardware interrupts create an interrupt storm window? If the hypervisor asserts an interrupt during synchronize_net(), the hardware IRQ handler runs. Since NAPI is disabled, it returns IRQ_HANDLED without masking the interrupt source at the hypervisor, leading immediately to an IRQ storm and CPU lockup. > + > + rc = netif_set_real_num_rx_queues(netdev, new_count); > + if (rc) { > + netdev_err(netdev, "Failed to set real RX queues to %d: %d\n", > + new_count, rc); > + for (i = new_count; i < old_count; i++) > + napi_enable(&adapter->napi[i]); > + return rc; > + } [Severity: High] Is it possible for this error path to permanently stall the RX queues? It calls napi_enable() but doesn't call ibmveth_replenish_task(). Since the queues were completely drained of their buffers by ibmveth_drain_rx_queue(), will the hypervisor have any buffers to place incoming packets? Without buffers, no interrupts will fire for these queues, and NAPI will never run again.