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Thu, 9 Jan 2020 11:32:33 +0000 (UTC) Subject: Re: [PATCH for-5.0 v11 08/20] virtio-iommu: Implement translate To: Jean-Philippe Brucker References: <20191220162642.GA2626852@myrica> <20191220165100.GA3780@xz-x1> <20200106170634.GF2062@myrica> <20200106175850.GC219677@xz-x1> <20200107101024.GB832497@myrica> <20200109084700.GA934975@myrica> <0beb9d61-05b8-3152-e967-64413def6ab7@redhat.com> <20200109104032.GA937123@myrica> <20200109111544.GA940335@myrica> From: Auger Eric Message-ID: <97e245bc-21f6-74c8-c147-65bbed7ef906@redhat.com> Date: Thu, 9 Jan 2020 12:32:32 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20200109111544.GA940335@myrica> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-MC-Unique: 0Zd6EqyIOgCzeSguV0Q55w-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: yang.zhong@intel.com, peter.maydell@linaro.org, kevin.tian@intel.com, tnowicki@marvell.com, mst@redhat.com, jean-philippe.brucker@arm.com, quintela@redhat.com, qemu-devel@nongnu.org, Peter Xu , armbru@redhat.com, bharatb.linux@gmail.com, qemu-arm@nongnu.org, dgilbert@redhat.com, eric.auger.pro@gmail.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Jean, On 1/9/20 12:15 PM, Jean-Philippe Brucker wrote: > On Thu, Jan 09, 2020 at 12:01:26PM +0100, Auger Eric wrote: >> Hi, >> >> On 1/9/20 11:40 AM, Jean-Philippe Brucker wrote: >>> On Thu, Jan 09, 2020 at 09:58:49AM +0100, Auger Eric wrote: >>>>>> I share Peter's concern about having a different default policy than x86. >>>>> >>>>> Yes I'd say just align with whatever policy is already in place. Do you >>>>> think we could add a command-line option to let people disable >>>>> default-bypass, though? That would be a convenient way to make the IOMMU >>>>> protection airtight for those who need it. >>>> Yes I could easily add a device option to disable the default bypass. >>>> >>>> Shall we change the meaning of the F_BYPASS feature then? If exposed by >>>> the device, the device does bypass by default, otherwise it doesn't. >>>> This would be controlled by the device option. >>> >>> For a device that doesn't do bypass by default, the driver wouldn't have >>> the ability to enable bypass (feature bit not offered, not negotiable). >>> >>>> The driver then could have means to overwrite this behavior once loaded? >>> >>> Let's keep the bypass feature bit for this. If the bit is offered, the >>> driver chooses to enable or disable it. If the bit is not offered or not >>> negotiated, then the behavior is deny. If the bit is offered and >>> negotiated then the behavior is allow. >>> >>> We can say that before features negotiation (latched at features register >>> write, I think, in practice?) the behavior is platform dependent. The >>> current wording about bypass intends to discourage unsafe choices but >>> makes a strong statement only about the device behavior after features >>> negotiation. >> OK. May be worth adding in the spec later. >> >> By the way what is the plan for the vote? > > The ballot closed and the spec is accepted for virtio-v1.2-cs01, with the > condition that the stale statement about padding is removed > (https://lists.oasis-open.org/archives/virtio-dev/201911/msg00083.html) Ah OK. Sorry I missed the outcome. Congratulations! Eric > > Thanks, > Jean >