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 E936A14D29C for ; Tue, 23 Jul 2024 11:04:21 +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=1721732663; cv=none; b=GymyG7h6k4ZCH2sZQeoMhNtN5BsBleaCRfWuHaEiGK8xwkHaHbcZwnO6KvzuDo5AMSWJOCKk5UA02ja4wGNqWu9xi/geoZg1puNPiNt/37qISaXlfYD8mF+dJ7bMBp37GJ+9QSx/zliRH4QIMaC0VoBOjGA2XKwjG7RNX3tatwI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721732663; c=relaxed/simple; bh=6hACR6MxAj1NYC11Q1DxFcypWZd5B93E3TgTVAa/GOU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: In-Reply-To:Content-Type:Content-Disposition; b=XVLP8rSC6BjP77d/iuTEvtBgsNNxWeqEV3Ap7jRxDLt7TFKUbLgIN9LXrMBMWg5y/j1JG+umte9pPGqvJzfPJN4odfZxsSWNF9yImRZNGe5pQOc/Pvjo2ouFR8lxt+7chQKUy1lun7Uo0jTEbcmIsWHjGNoeevd8zGHAC2YpjYQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none 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=buhCbNCB; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none 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="buhCbNCB" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1721732661; 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=CwTb7hnD8qNwiBtvtGGixQf/Bn3HIMxKUDzIwfA0Aws=; b=buhCbNCBNu9L8cU6faET/HJ47GZ+95qan4xPwASvcqou1zDWX7tm8ud34iD//LfZTRky7A CQf7qrz43ABfr5DvE4hBWBThAQRm9tJeqBELHSpjhJFbdRrVW9Znto7iPB2vUXQY79wsUi IzaEDoo7R90dnrrLQtqgLYCsNQMem3g= Received: from mail-ej1-f70.google.com (mail-ej1-f70.google.com [209.85.218.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-480-gHYwbAf4MD6HCfItVMIq3A-1; Tue, 23 Jul 2024 07:04:19 -0400 X-MC-Unique: gHYwbAf4MD6HCfItVMIq3A-1 Received: by mail-ej1-f70.google.com with SMTP id a640c23a62f3a-a797c5b4f47so51595166b.2 for ; Tue, 23 Jul 2024 04:04:19 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1721732658; x=1722337458; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=CwTb7hnD8qNwiBtvtGGixQf/Bn3HIMxKUDzIwfA0Aws=; b=uLb4nTtPATAXdqgJDxCjsdwFz4RSoKn6ACs5FNeelhKWCUhOEIna2jYw0MRIebLiSJ 4WRvH4nvwFfihX2xT2s8MiDseaaz3aMXsvugZkQqUbCAAKPJ5BLLEfIZMrOdIFAylFd/ /ao2jRkuL8L3SFg5tLcweB7QHzoJm9RuApAEFKFeHWfORUZ5iIFT2GYlLvUfGWPjYnqU Qb0erSeQ9gRX+iL2d/Zc2t8dEJcOnlXMAgQgCfGZtKneOTlgPKHvLecjE6E7vx6y/xF2 o18LbhCKYfVf9/C+nvta9/mb5FGYPY2JXR0R65nGgBFjx84ANtuvXb1BNNaG03m+ASaE PH8g== X-Forwarded-Encrypted: i=1; AJvYcCV2WpflMZjk0X+vzKxzQV8jEo5EB4p3TG1LvlqVr2eXmHL7uPfTYyAWrwQDyigPNtNPoZB52GucuAuINy6CMmUur+LrfHilnff4sFWctjM= X-Gm-Message-State: AOJu0Yw4OwpL5wre0D/i0+SIv/G53xpMMtS7bI7IxqnVmJmb+ID/3+5p zUrGlMEaujRDbo9wgJ9vitY2QLgTkse9LZIamDJB1nk/vv3zNdOZ6kl/SkALRRSHA/DAfBzHHf+ pibyweveMkPWcHUStMP9NcQXXUgq4s72zRUKM6NPYpRfQZ5cP3P1Nbnataw7MXOge X-Received: by 2002:a17:906:7315:b0:a77:dbe2:31ff with SMTP id a640c23a62f3a-a7a4c4326ddmr652980366b.66.1721732658217; Tue, 23 Jul 2024 04:04:18 -0700 (PDT) X-Google-Smtp-Source: AGHT+IG9GOmzLADn5ttFoMePb46sE7uLr7blKeRCjyBahlXRvTEqNvkNRYIcfhXkKRQ6ebd1fZXamw== X-Received: by 2002:a17:906:7315:b0:a77:dbe2:31ff with SMTP id a640c23a62f3a-a7a4c4326ddmr652976666b.66.1721732657405; Tue, 23 Jul 2024 04:04:17 -0700 (PDT) Received: from redhat.com ([2a0d:6fc7:440:9c9a:ffee:509d:1766:aa7f]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a7a3c951004sm524265966b.223.2024.07.23.04.04.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Jul 2024 04:04:16 -0700 (PDT) Date: Tue, 23 Jul 2024 07:04:07 -0400 From: "Michael S. Tsirkin" To: Srujana Challa Cc: Jason Wang , "virtualization@lists.linux.dev" , "kvm@vger.kernel.org" , Vamsi Krishna Attunuru , Shijith Thotton , Nithin Kumar Dabilpuram , Jerin Jacob , "joro@8bytes.org" , "will@kernel.org" Subject: Re: [EXTERNAL] Re: [PATCH] vdpa: Add support for no-IOMMU mode Message-ID: <20240723070326-mutt-send-email-mst@kernel.org> References: <20240530101823.1210161-1-schalla@marvell.com> <20240717054547-mutt-send-email-mst@kernel.org> <20240722034957-mutt-send-email-mst@kernel.org> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit On Tue, Jul 23, 2024 at 07:10:52AM +0000, Srujana Challa wrote: > > On Mon, Jul 22, 2024 at 03:22:22PM +0800, Jason Wang wrote: > > > On Fri, Jul 19, 2024 at 11:40 PM Srujana Challa > > wrote: > > > > > > > > > On Thu, May 30, 2024 at 03:48:23PM +0530, Srujana Challa wrote: > > > > > > This commit introduces support for an UNSAFE, no-IOMMU mode in > > > > > > the vhost-vdpa driver. When enabled, this mode provides no > > > > > > device isolation, no DMA translation, no host kernel protection, > > > > > > and cannot be used for device assignment to virtual machines. It > > > > > > requires RAWIO permissions and will taint the kernel. > > > > > > This mode requires enabling the > > > > > "enable_vhost_vdpa_unsafe_noiommu_mode" > > > > > > option on the vhost-vdpa driver. This mode would be useful to > > > > > > get better performance on specifice low end machines and can be > > > > > > leveraged by embedded platforms where applications run in controlled > > environment. > > > > > > > > > > > > Signed-off-by: Srujana Challa > > > > > > > > > > Thought hard about that. > > > > > I think given vfio supports this, we can do that too, and the extension is > > small. > > > > > > > > > > However, it looks like setting this parameter will automatically > > > > > change the behaviour for existing userspace when > > IOMMU_DOMAIN_IDENTITY is set. > Our initial thought was to support only for no-iommu case, in which domain itself > won't be exist. So, we can modify the code as below to check for only presence of domain. > I think, only handling of no-iommu case wouldn't effect the existing userspace. > + if ((!domain) && vhost_vdpa_noiommu && capable(CAP_SYS_RAWIO)) { I would prefer some explicit action. Just not specifying a domain is something I'd like to keep reserved for something of more wide usefulness. > > > > > > > > > > I suggest a new domain type for use just for this purpose. > > > > > > I'm not sure I get this, we want to bypass IOMMU, so it doesn't even > > > have a doman. > > > > yes, a fake one. or come up with some other flag that userspace will set. > > > > > > This way if host has > > > > > an iommu, then the same kernel can run both VMs with isolation and > > > > > unsafe embedded apps without. > > > > Could you provide further details on this concept? What criteria > > > > would determine the configuration of the new domain type? Would this > > > > require a boot parameter similar to IOMMU_DOMAIN_IDENTITY, such as > > iommu.passthrough=1 or iommu.pt? > > > > > > Thanks > > > > > > > > > > > > > > --- > > > > > > drivers/vhost/vdpa.c | 23 +++++++++++++++++++++++ > > > > > > 1 file changed, 23 insertions(+) > > > > > > > > > > > > diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c index > > > > > > bc4a51e4638b..d071c30125aa 100644 > > > > > > --- a/drivers/vhost/vdpa.c > > > > > > +++ b/drivers/vhost/vdpa.c > > > > > > @@ -36,6 +36,11 @@ enum { > > > > > > > > > > > > #define VHOST_VDPA_IOTLB_BUCKETS 16 > > > > > > > > > > > > +bool vhost_vdpa_noiommu; > > > > > > +module_param_named(enable_vhost_vdpa_unsafe_noiommu_mode, > > > > > > + vhost_vdpa_noiommu, bool, 0644); > > > > > > +MODULE_PARM_DESC(enable_vhost_vdpa_unsafe_noiommu_mode, > > > > > "Enable > > > > > > +UNSAFE, no-IOMMU mode. This mode provides no device isolation, > > > > > > +no DMA translation, no host kernel protection, cannot be used > > > > > > +for device assignment to virtual machines, requires RAWIO > > > > > > +permissions, and will taint the kernel. If you do not know what this is > > for, step away. > > > > > > +(default: false)"); > > > > > > + > > > > > > struct vhost_vdpa_as { > > > > > > struct hlist_node hash_link; > > > > > > struct vhost_iotlb iotlb; > > > > > > @@ -60,6 +65,7 @@ struct vhost_vdpa { > > > > > > struct vdpa_iova_range range; > > > > > > u32 batch_asid; > > > > > > bool suspended; > > > > > > + bool noiommu_en; > > > > > > }; > > > > > > > > > > > > static DEFINE_IDA(vhost_vdpa_ida); @@ -887,6 +893,10 @@ static > > > > > > void vhost_vdpa_general_unmap(struct vhost_vdpa *v, { > > > > > > struct vdpa_device *vdpa = v->vdpa; > > > > > > const struct vdpa_config_ops *ops = vdpa->config; > > > > > > + > > > > > > + if (v->noiommu_en) > > > > > > + return; > > > > > > + > > > > > > if (ops->dma_map) { > > > > > > ops->dma_unmap(vdpa, asid, map->start, map->size); > > > > > > } else if (ops->set_map == NULL) { @@ -980,6 +990,9 @@ > > > > > > static int vhost_vdpa_map(struct vhost_vdpa *v, > > > > > struct vhost_iotlb *iotlb, > > > > > > if (r) > > > > > > return r; > > > > > > > > > > > > + if (v->noiommu_en) > > > > > > + goto skip_map; > > > > > > + > > > > > > if (ops->dma_map) { > > > > > > r = ops->dma_map(vdpa, asid, iova, size, pa, perm, opaque); > > > > > > } else if (ops->set_map) { > > > > > > @@ -995,6 +1008,7 @@ static int vhost_vdpa_map(struct vhost_vdpa > > > > > > *v, > > > > > struct vhost_iotlb *iotlb, > > > > > > return r; > > > > > > } > > > > > > > > > > > > +skip_map: > > > > > > if (!vdpa->use_va) > > > > > > atomic64_add(PFN_DOWN(size), &dev->mm->pinned_vm); > > > > > > > > > > > > @@ -1298,6 +1312,7 @@ static int vhost_vdpa_alloc_domain(struct > > > > > vhost_vdpa *v) > > > > > > struct vdpa_device *vdpa = v->vdpa; > > > > > > const struct vdpa_config_ops *ops = vdpa->config; > > > > > > struct device *dma_dev = vdpa_get_dma_dev(vdpa); > > > > > > + struct iommu_domain *domain; > > > > > > const struct bus_type *bus; > > > > > > int ret; > > > > > > > > > > > > @@ -1305,6 +1320,14 @@ static int vhost_vdpa_alloc_domain(struct > > > > > vhost_vdpa *v) > > > > > > if (ops->set_map || ops->dma_map) > > > > > > return 0; > > > > > > > > > > > > + domain = iommu_get_domain_for_dev(dma_dev); > > > > > > + if ((!domain || domain->type == IOMMU_DOMAIN_IDENTITY) && > > > > > > + vhost_vdpa_noiommu && capable(CAP_SYS_RAWIO)) { > > > > > > > > > > So if userspace does not have CAP_SYS_RAWIO instead of failing > > > > > with a permission error the functionality changes silently? > > > > > That's confusing, I think. > > > > Yes, you are correct. I will modify the code to return error when > > > > vhost_vdpa_noiommu is set and CAP_SYS_RAWIO is not set. > > > > > > > > Thanks. > > > > > > > > > > > > > > > > + add_taint(TAINT_USER, LOCKDEP_STILL_OK); > > > > > > + dev_warn(&v->dev, "Adding kernel taint for noiommu > > > > > > + on > > > > > device\n"); > > > > > > + v->noiommu_en = true; > > > > > > + return 0; > > > > > > + } > > > > > > bus = dma_dev->bus; > > > > > > if (!bus) > > > > > > return -EFAULT; > > > > > > -- > > > > > > 2.25.1 > > > > >