Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [RFC PATCH 2/3] vfio/hisilicon: register the driver to vfio
To:     Jason Gunthorpe <jgg@nvidia.com>
CC:     Alex Williamson <alex.williamson@redhat.com>, <cohuck@redhat.com>,
        <linux-kernel@vger.kernel.org>, <linuxarm@openeuler.org>
References: <1618284983-55581-3-git-send-email-liulongfang@huawei.com>
 <20210415220137.GA1672608@nvidia.com>
 <10d53c5d-e6d5-a165-84b2-eaf8a3b7dcce@huawei.com>
 <20210419123314.GT1370958@nvidia.com>
 <00c4fa43-21fa-a48b-b95d-a2310ffab725@huawei.com>
 <20210420125957.GA1370958@nvidia.com>
 <20210420160457.6b91850a@x1.home.shazbot.org>
 <25d033e6-1cba-0da0-2ee7-03a14e75b8a5@huawei.com>
 <20210421121224.62382e5d@redhat.com>
 <6ea89655-31c5-233b-ca2a-fcc166b5597c@huawei.com>
 <20210512121053.GT1002214@nvidia.com>
From:   liulongfang <liulongfang@huawei.com>
Message-ID: <3eaa3114-81b6-1bd9-c7e6-cb1541389b58@huawei.com>
Date:   Thu, 13 May 2021 10:08:28 +0800
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101
 Thunderbird/60.8.0
MIME-Version: 1.0
In-Reply-To: <20210512121053.GT1002214@nvidia.com>
Content-Type: text/plain; charset="gbk"
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 2021/5/12 20:10, Jason Gunthorpe wrote:
> On Wed, May 12, 2021 at 04:39:43PM +0800, liulongfang wrote:
> 
>> Therefore, this method of limiting the length of the BAR
>> configuration space can prevent unsafe operations of the memory.
> 
> The issue is DMA controlled by the guest accessing the secure BAR
> area, not the guest CPU.
> 
> Jason
> .
> 
This secure BAR area is not presented to the Guest,
which makes it impossible for the Guest to obtain the secure BAR area
when establishing the DMA mapping of the configuration space.
If the DMA controller accesses the secure BAR area, the access will
be blocked by the SMMU.

Thanks
Longfang.