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=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 B74A3C433F5 for ; Mon, 6 Sep 2021 07:07:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 967D460F92 for ; Mon, 6 Sep 2021 07:07:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239955AbhIFHIE (ORCPT ); Mon, 6 Sep 2021 03:08:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44860 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239792AbhIFHIB (ORCPT ); Mon, 6 Sep 2021 03:08:01 -0400 Received: from mail-ej1-x636.google.com (mail-ej1-x636.google.com [IPv6:2a00:1450:4864:20::636]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C5E18C0613C1 for ; Mon, 6 Sep 2021 00:06:56 -0700 (PDT) Received: by mail-ej1-x636.google.com with SMTP id e21so11429969ejz.12 for ; Mon, 06 Sep 2021 00:06:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Q3MG6YTB+QzDfQAiZySr2rS0jN8YaIk13obJQJ/stWo=; b=lkQZaa6g9ei4zhefeS4/oyNQrJS2xco6ilGBKyKlZ6vC0SUD8QQ+1knPvpyi6IaHac GqpF6T/J9e8UZEhbRcxYY2Vqkdxa9S0Mc6OSDQEPV8Lm2RG5xwllvm/ICW7ihxTyN8cQ 6q8HxGdwJRriwFkXrBLniQ+rOGGSciTVwRPaZN0SjIEyZqVJuZ/w0QfR4/wBg4GuaIvK u5g1glJnwNcAurESAAaeIz8Og+r0qqEHDRcUcXNFnSlIosPcpoHpNITG9ICSkR9Z8ltb ne8SJRTHipR+XIW/F978DLyiAT4QKN6N8mAAM4madRU69d+NI8I3REMHopnFJfCrL03M 8PUQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Q3MG6YTB+QzDfQAiZySr2rS0jN8YaIk13obJQJ/stWo=; b=Pt9JciLohkd+tG/k68Hm1HK3yNBoBaeEDRw/P9smw+L1oo2t9V+cPVFsnnqBoQbPyU QuxuFbUpO/b3wFN/vmzTm2gryde6w9PcdWgU0yrsU5a1NsNchRSo3+8wUe+u5Q3O0R7h /GBgqqB6MqocvJOVrmf7jFoH51NZwdmX2jAEKSjxVCW+Yf1wRehPookjr6LqmO0F5Vdr 5Nap1xnnC+Ur9gHafKz4l83f55DIUsOPOUiY2QJmpwHifsb51dpbnF35X2WS7RMNV2QE NAlcK6ZT9BIZWC+BSAY+nQUpzCbuB73HpKLyqtoph/zV/KLKeKnttGbwQ1jq6/fljL0F gwlg== X-Gm-Message-State: AOAM530VpNKId2tfDKzmZkoXNSCikybDKO7XE30FJKCJVYNxUGeV8JMy VGq0HBkqc5XA5JzZzfYoPud3cTciKNonENEL6cvg X-Google-Smtp-Source: ABdhPJywBwaaVm3boucqd1sdO/Cfi8IGS0P4Me7y+BCi/2fL1YgT6rXVQRK94JvNPY5a+i9h1dktiuFSZgpWUJHXv74= X-Received: by 2002:a17:906:8da:: with SMTP id o26mr12057282eje.424.1630912015321; Mon, 06 Sep 2021 00:06:55 -0700 (PDT) MIME-Version: 1.0 References: <20210831103634.33-1-xieyongji@bytedance.com> <20210831103634.33-6-xieyongji@bytedance.com> <20210906015524-mutt-send-email-mst@kernel.org> <20210906023131-mutt-send-email-mst@kernel.org> In-Reply-To: <20210906023131-mutt-send-email-mst@kernel.org> From: Yongji Xie Date: Mon, 6 Sep 2021 15:06:44 +0800 Message-ID: Subject: Re: [PATCH v13 05/13] vdpa: Add reset callback in vdpa_config_ops To: "Michael S. Tsirkin" Cc: Jason Wang , Stefan Hajnoczi , Stefano Garzarella , Parav Pandit , Christoph Hellwig , Christian Brauner , Randy Dunlap , Matthew Wilcox , Al Viro , Jens Axboe , bcrl@kvack.org, Jonathan Corbet , =?UTF-8?Q?Mika_Penttil=C3=A4?= , Dan Carpenter , joro@8bytes.org, Greg KH , He Zhe , Liu Xiaodong , Joe Perches , Robin Murphy , Will Deacon , John Garry , songmuchun@bytedance.com, virtualization , netdev@vger.kernel.org, kvm , linux-fsdevel@vger.kernel.org, iommu@lists.linux-foundation.org, linux-kernel Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 6, 2021 at 2:37 PM Michael S. Tsirkin wrote: > > On Mon, Sep 06, 2021 at 02:09:25PM +0800, Yongji Xie wrote: > > On Mon, Sep 6, 2021 at 1:56 PM Michael S. Tsirkin wrote: > > > > > > On Tue, Aug 31, 2021 at 06:36:26PM +0800, Xie Yongji wrote: > > > > This adds a new callback to support device specific reset > > > > behavior. The vdpa bus driver will call the reset function > > > > instead of setting status to zero during resetting. > > > > > > > > Signed-off-by: Xie Yongji > > > > > > > > > This does gloss over a significant change though: > > > > > > > > > > --- > > > > @@ -348,12 +352,12 @@ static inline struct device *vdpa_get_dma_dev(struct vdpa_device *vdev) > > > > return vdev->dma_dev; > > > > } > > > > > > > > -static inline void vdpa_reset(struct vdpa_device *vdev) > > > > +static inline int vdpa_reset(struct vdpa_device *vdev) > > > > { > > > > const struct vdpa_config_ops *ops = vdev->config; > > > > > > > > vdev->features_valid = false; > > > > - ops->set_status(vdev, 0); > > > > + return ops->reset(vdev); > > > > } > > > > > > > > static inline int vdpa_set_features(struct vdpa_device *vdev, u64 features) > > > > > > > > > Unfortunately this breaks virtio_vdpa: > > > > > > > > > static void virtio_vdpa_reset(struct virtio_device *vdev) > > > { > > > struct vdpa_device *vdpa = vd_get_vdpa(vdev); > > > > > > vdpa_reset(vdpa); > > > } > > > > > > > > > and there's no easy way to fix this, kernel can't recover > > > from a reset failure e.g. during driver unbind. > > > > > > > Yes, but it should be safe with the protection of software IOTLB even > > if the reset() fails during driver unbind. > > > > Thanks, > > Yongji > > Hmm. I don't see it. > What exactly will happen? What prevents device from poking at > memory after reset? Note that dma unmap in e.g. del_vqs happens > too late. But I didn't see any problems with touching the memory for virtqueues. The memory should not be freed after dma unmap? And the memory for the bounce buffer should also be safe to be accessed by userspace in this case. > And what about e.g. interrupts? > E.g. we have this: > > /* Virtqueues are stopped, nothing can use vblk->vdev anymore. */ > vblk->vdev = NULL; > > and this is no longer true at this point. > You're right. But I didn't see where the interrupt handler will use the vblk->vdev. So it seems to be not too late to fix it: diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c index 5c25ff6483ad..ea41a7389a26 100644 --- a/drivers/vdpa/vdpa_user/vduse_dev.c +++ b/drivers/vdpa/vdpa_user/vduse_dev.c @@ -665,13 +665,13 @@ static void vduse_vdpa_set_config(struct vdpa_device *vdpa, unsigned int offset, static int vduse_vdpa_reset(struct vdpa_device *vdpa) { struct vduse_dev *dev = vdpa_to_vduse(vdpa); + int ret; - if (vduse_dev_set_status(dev, 0)) - return -EIO; + ret = vduse_dev_set_status(dev, 0); vduse_dev_reset(dev); - return 0; + return ret; } static u32 vduse_vdpa_get_generation(struct vdpa_device *vdpa) Thanks, Yongji