From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 99CE7C433E0 for ; Mon, 1 Feb 2021 06:04:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4104964E2E for ; Mon, 1 Feb 2021 06:04:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232071AbhBAGE0 (ORCPT ); Mon, 1 Feb 2021 01:04:26 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:58117 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231861AbhBAGCT (ORCPT ); Mon, 1 Feb 2021 01:02:19 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612159249; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=RdybqpikUstylFnotQy48gGt+VsHUqQDR1hNUpuuxFI=; b=cso1UdoPDaebNbLQ/LWWCuUfHEGGzLPeoiaLGrYF5F0Di5u3GSEXBzIsPHcQXEE5emTX0u 89Pj98AaTwLekwZc051B/67YFjb7jIbpQ79mQWjif+56UkZZISLnGprvmu6JLkytA/QyWS kdoSKUrkFfb7VUOJ5zN9wPzMZmPhfic= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-241-fAEQBVTOOKuxJMlZzKKzzQ-1; Mon, 01 Feb 2021 01:00:46 -0500 X-MC-Unique: fAEQBVTOOKuxJMlZzKKzzQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id ED10D800D62; Mon, 1 Feb 2021 06:00:44 +0000 (UTC) Received: from [10.72.13.120] (ovpn-13-120.pek2.redhat.com [10.72.13.120]) by smtp.corp.redhat.com (Postfix) with ESMTP id A339A1001281; Mon, 1 Feb 2021 06:00:37 +0000 (UTC) Subject: Re: [PATCH 2/2] vdpa/mlx5: Restore the hardware used index after change map To: Eli Cohen Cc: mst@redhat.com, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, lulu@redhat.com References: <20210128134130.3051-1-elic@nvidia.com> <20210128134130.3051-3-elic@nvidia.com> <54239b51-918c-3475-dc88-4da1a4548da8@redhat.com> <20210131185536.GA164217@mtl-vdi-166.wap.labs.mlnx> <0c99f35c-7644-7201-cd11-7d486389a182@redhat.com> <20210201055247.GA184807@mtl-vdi-166.wap.labs.mlnx> From: Jason Wang Message-ID: Date: Mon, 1 Feb 2021 14:00:35 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210201055247.GA184807@mtl-vdi-166.wap.labs.mlnx> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 2021/2/1 下午1:52, Eli Cohen wrote: > On Mon, Feb 01, 2021 at 11:36:23AM +0800, Jason Wang wrote: >> On 2021/2/1 上午2:55, Eli Cohen wrote: >>> On Fri, Jan 29, 2021 at 11:49:45AM +0800, Jason Wang wrote: >>>> On 2021/1/28 下午9:41, Eli Cohen wrote: >>>>> When a change of memory map occurs, the hardware resources are destroyed >>>>> and then re-created again with the new memory map. In such case, we need >>>>> to restore the hardware available and used indices. The driver failed to >>>>> restore the used index which is added here. >>>>> >>>>> Fixes 1a86b377aa21 ("vdpa/mlx5: Add VDPA driver for supported mlx5 devices") >>>>> Signed-off-by: Eli Cohen >>>> A question. Does this mean after a vq is suspended, the hw used index is not >>>> equal to vq used index? >>> Surely there is just one "Used index" for a VQ. What I was trying to say >>> is that after the VQ is suspended, I read the used index by querying the >>> hardware. The read result is the used index that the hardware wrote to >>> memory. >> >> Just to make sure I understand here. So it looks to me we had two index. The >> first is the used index which is stored in the memory/virtqueue, the second >> is the one that is stored by the device. >> > It is the structures defined in the virtio spec in 2.6.6 for the > available ring and 2.6.8 for the used ring. As you know these the > available ring is written to by the driver and read by the device. The > opposite happens for the used index. Right, so for used index it was wrote by device. And the device should have an internal used index value that is used to write to the used ring. And the code is used to sync the device internal used index if I understand this correctly. > The reason I need to restore the last known indices is for the new > hardware objects to sync on the last state and take over from there. Right, after the vq suspending, the questions are: 1) is hardware internal used index might not be the same with the used index in the virtqueue? or 2) can we simply sync the virtqueue's used index to the hardware's used index? Thanks > >>> After the I create the new hardware object, I need to tell it >>> what is the used index (and the available index) as a way to sync it >>> with the existing VQ. >> >> For avail index I understand that the hardware index is not synced with the >> avail index stored in the memory/virtqueue. The question is used index, if >> the hardware one is not synced with the one in the virtqueue. It means after >> vq is suspended,  some requests is not completed by the hardware (e.g the >> buffer were not put to used ring). >> >> This may have implications to live migration, it means those unaccomplished >> requests needs to be migrated to the destination and resubmitted to the >> device. This looks not easy. >> >> Thanks >> >> >>> This sync is especially important when a change of map occurs while the >>> VQ was already used (hence the indices are likely to be non zero). This >>> can be triggered by hot adding memory after the VQs have been used. >>> >>>> Thanks >>>> >>>> >>>>> --- >>>>> drivers/vdpa/mlx5/net/mlx5_vnet.c | 7 +++++++ >>>>> 1 file changed, 7 insertions(+) >>>>> >>>>> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c >>>>> index 549ded074ff3..3fc8588cecae 100644 >>>>> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c >>>>> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c >>>>> @@ -87,6 +87,7 @@ struct mlx5_vq_restore_info { >>>>> u64 device_addr; >>>>> u64 driver_addr; >>>>> u16 avail_index; >>>>> + u16 used_index; >>>>> bool ready; >>>>> struct vdpa_callback cb; >>>>> bool restore; >>>>> @@ -121,6 +122,7 @@ struct mlx5_vdpa_virtqueue { >>>>> u32 virtq_id; >>>>> struct mlx5_vdpa_net *ndev; >>>>> u16 avail_idx; >>>>> + u16 used_idx; >>>>> int fw_state; >>>>> /* keep last in the struct */ >>>>> @@ -804,6 +806,7 @@ static int create_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtque >>>>> obj_context = MLX5_ADDR_OF(create_virtio_net_q_in, in, obj_context); >>>>> MLX5_SET(virtio_net_q_object, obj_context, hw_available_index, mvq->avail_idx); >>>>> + MLX5_SET(virtio_net_q_object, obj_context, hw_used_index, mvq->used_idx); >>>>> MLX5_SET(virtio_net_q_object, obj_context, queue_feature_bit_mask_12_3, >>>>> get_features_12_3(ndev->mvdev.actual_features)); >>>>> vq_ctx = MLX5_ADDR_OF(virtio_net_q_object, obj_context, virtio_q_context); >>>>> @@ -1022,6 +1025,7 @@ static int connect_qps(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *m >>>>> struct mlx5_virtq_attr { >>>>> u8 state; >>>>> u16 available_index; >>>>> + u16 used_index; >>>>> }; >>>>> static int query_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *mvq, >>>>> @@ -1052,6 +1056,7 @@ static int query_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueu >>>>> memset(attr, 0, sizeof(*attr)); >>>>> attr->state = MLX5_GET(virtio_net_q_object, obj_context, state); >>>>> attr->available_index = MLX5_GET(virtio_net_q_object, obj_context, hw_available_index); >>>>> + attr->used_index = MLX5_GET(virtio_net_q_object, obj_context, hw_used_index); >>>>> kfree(out); >>>>> return 0; >>>>> @@ -1602,6 +1607,7 @@ static int save_channel_info(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqu >>>>> return err; >>>>> ri->avail_index = attr.available_index; >>>>> + ri->used_index = attr.used_index; >>>>> ri->ready = mvq->ready; >>>>> ri->num_ent = mvq->num_ent; >>>>> ri->desc_addr = mvq->desc_addr; >>>>> @@ -1646,6 +1652,7 @@ static void restore_channels_info(struct mlx5_vdpa_net *ndev) >>>>> continue; >>>>> mvq->avail_idx = ri->avail_index; >>>>> + mvq->used_idx = ri->used_index; >>>>> mvq->ready = ri->ready; >>>>> mvq->num_ent = ri->num_ent; >>>>> mvq->desc_addr = ri->desc_addr;