From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966552AbeCAItM (ORCPT ); Thu, 1 Mar 2018 03:49:12 -0500 Received: from mail-lf0-f65.google.com ([209.85.215.65]:36986 "EHLO mail-lf0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965838AbeCAItL (ORCPT ); Thu, 1 Mar 2018 03:49:11 -0500 X-Google-Smtp-Source: AG47ELuIWvjzCfDJssUd5SYDu36HjmGYPl0gut0ccUmtSt4xdc3jzaVuRJ6zgLpGjvFGp7qlyDbevA== Subject: Re: [PATCH 0/9] drm/xen-front: Add support for Xen PV display frontend To: Gerd Hoffmann Cc: xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, airlied@linux.ie, daniel.vetter@intel.com, seanpaul@chromium.org, gustavo@padovan.org, jgross@suse.com, boris.ostrovsky@oracle.com, konrad.wilk@oracle.com, Oleksandr Andrushchenko References: <1519200222-20623-1-git-send-email-andr2000@gmail.com> <4c7e6f65-1787-3815-22b5-f9495e388c06@gmail.com> <7e265c53-db9a-0946-6b1c-b946bcbb4100@gmail.com> <20180301082648.frnslqyhffj2bkwl@sirius.home.kraxel.org> From: Oleksandr Andrushchenko Message-ID: Date: Thu, 1 Mar 2018 10:49:07 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180301082648.frnslqyhffj2bkwl@sirius.home.kraxel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/01/2018 10:26 AM, Gerd Hoffmann wrote: > Hi, > >> 1. Possible security issues - VirtIO devices are PCI bus masters, thus >> allowing real device (running, for example, in untrusted driver domain) >> to get control over guest's memory by writing to its memory >> >> 2. VirtIO currently uses GFNs written into the shared ring, without Xen >> grants support. This will require generic grant-mapping/sharing layer >> to be added to VirtIO. >> >> 3. VirtIO requires QEMU PCI emulation for setting up a device. Xen PV >> (and PVH) domains don't use QEMU for platform emulation in order to >> reduce attack surface. (PVH is in the process of gaining PCI config >> space emulation though, but it is optional, not a requirement) > Well, that is wrong. virtio doesn't require pci. There are other > transports (mmio, ccw), and it should be possible to create a xen > specific transport which uses grant tables properly. You are correct, PCI is not a requirement here > Seems there even > was an attempt to implement that in 2011, see > https://wiki.xenproject.org/wiki/Virtio_On_Xen And even more, that was also raised at Linux Plumbers Conference 2013 [1]. But still, there is no implementation available >> 4. Most of the PV drivers a guest uses at the moment are Xen PV drivers, >> e.g. net, >> block, console, so only virtio-gpu will require QEMU to run. > You are not forced to use qemu, you can certainly create an alternative > host side implementation (and still use on the existing virtio guest > drivers). Yes, this is true. We also discussed virtio with Xen community, Stefano Stabellini says: "the issues with virtio are (in order of seriousness): 1) virtio assumes that the backend is able to map any page in memory In other words, it is not possible to do driver domains with virtio 2) virtio doesn't work with PV guests, only HVM (I think PVH would have   the same issue) Virtio does synchronous IO emulation. QEMU for PV guests is not capable of handling synchronous IO requests. The infratructure is just not there. 3) virtio performance is poor with Xen There are multiple reasons for this, but the main one is that the backends are in QEMU, running in Dom0. They become the bottleneck quickly. " > Whenever writing a xenbus implementation for both guest and host or > writing a virtio implementation for the host only is better -- dunno. > The virtio path obviously needs some infrastructure work for virtio > support in Xen, which may pay off long term. Your call. Well, I do agree that long term virtio might be a better choice. But at the moment I still tend to have a dedicated Xen PV DRM implementation. That being said, I would kindly ask DRI community to review the driver and consider it for inclusion. > cheers, > Gerd > Thank you, Oleksandr Andrushchenko [1] https://www.youtube.com/watch?v=FcVDHBQInxA From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oleksandr Andrushchenko Subject: Re: [PATCH 0/9] drm/xen-front: Add support for Xen PV display frontend Date: Thu, 1 Mar 2018 10:49:07 +0200 Message-ID: References: <1519200222-20623-1-git-send-email-andr2000@gmail.com> <4c7e6f65-1787-3815-22b5-f9495e388c06@gmail.com> <7e265c53-db9a-0946-6b1c-b946bcbb4100@gmail.com> <20180301082648.frnslqyhffj2bkwl@sirius.home.kraxel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; Format="flowed" Content-Transfer-Encoding: base64 Return-path: Received: from mail-lf0-x242.google.com (mail-lf0-x242.google.com [IPv6:2a00:1450:4010:c07::242]) by gabe.freedesktop.org (Postfix) with ESMTPS id 6D5636E2D9 for ; Thu, 1 Mar 2018 08:49:11 +0000 (UTC) Received: by mail-lf0-x242.google.com with SMTP id g72so7637205lfg.3 for ; Thu, 01 Mar 2018 00:49:11 -0800 (PST) In-Reply-To: <20180301082648.frnslqyhffj2bkwl@sirius.home.kraxel.org> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Gerd Hoffmann Cc: jgross@suse.com, konrad.wilk@oracle.com, airlied@linux.ie, Oleksandr Andrushchenko , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, daniel.vetter@intel.com, xen-devel@lists.xenproject.org, boris.ostrovsky@oracle.com List-Id: dri-devel@lists.freedesktop.org T24gMDMvMDEvMjAxOCAxMDoyNiBBTSwgR2VyZCBIb2ZmbWFubiB3cm90ZToKPiAgICBIaSwKPgo+ PiAxLiBQb3NzaWJsZSBzZWN1cml0eSBpc3N1ZXMgLSBWaXJ0SU8gZGV2aWNlcyBhcmUgUENJIGJ1 cyBtYXN0ZXJzLCB0aHVzCj4+IGFsbG93aW5nIHJlYWwgZGV2aWNlIChydW5uaW5nLCBmb3IgZXhh bXBsZSwgaW4gdW50cnVzdGVkIGRyaXZlciBkb21haW4pCj4+IHRvIGdldCBjb250cm9sIG92ZXIg Z3Vlc3QncyBtZW1vcnkgYnkgd3JpdGluZyB0byBpdHMgbWVtb3J5Cj4+Cj4+IDIuIFZpcnRJTyBj dXJyZW50bHkgdXNlcyBHRk5zIHdyaXR0ZW4gaW50byB0aGUgc2hhcmVkIHJpbmcsIHdpdGhvdXQg WGVuCj4+IGdyYW50cyBzdXBwb3J0LiBUaGlzIHdpbGwgcmVxdWlyZSBnZW5lcmljIGdyYW50LW1h cHBpbmcvc2hhcmluZyBsYXllcgo+PiB0byBiZSBhZGRlZCB0byBWaXJ0SU8uCj4+Cj4+IDMuIFZp cnRJTyByZXF1aXJlcyBRRU1VIFBDSSBlbXVsYXRpb24gZm9yIHNldHRpbmcgdXAgYSBkZXZpY2Uu IFhlbiBQVgo+PiAoYW5kIFBWSCkgZG9tYWlucyBkb24ndCB1c2UgUUVNVSBmb3IgcGxhdGZvcm0g ZW11bGF0aW9uIGluIG9yZGVyIHRvCj4+IHJlZHVjZSBhdHRhY2sgc3VyZmFjZS4gIChQVkggaXMg aW4gdGhlIHByb2Nlc3Mgb2YgZ2FpbmluZyBQQ0kgY29uZmlnCj4+IHNwYWNlIGVtdWxhdGlvbiB0 aG91Z2gsIGJ1dCBpdCBpcyBvcHRpb25hbCwgbm90IGEgcmVxdWlyZW1lbnQpCj4gV2VsbCwgdGhh dCBpcyB3cm9uZy4gIHZpcnRpbyBkb2Vzbid0IHJlcXVpcmUgcGNpLiAgVGhlcmUgYXJlIG90aGVy Cj4gdHJhbnNwb3J0cyAobW1pbywgY2N3KSwgYW5kIGl0IHNob3VsZCBiZSBwb3NzaWJsZSB0byBj cmVhdGUgYSB4ZW4KPiBzcGVjaWZpYyB0cmFuc3BvcnQgd2hpY2ggdXNlcyBncmFudCB0YWJsZXMg cHJvcGVybHkuCllvdSBhcmUgY29ycmVjdCwgUENJIGlzIG5vdCBhIHJlcXVpcmVtZW50IGhlcmUK PiAgICBTZWVtcyB0aGVyZSBldmVuCj4gd2FzIGFuIGF0dGVtcHQgdG8gaW1wbGVtZW50IHRoYXQg aW4gMjAxMSwgc2VlCj4gaHR0cHM6Ly93aWtpLnhlbnByb2plY3Qub3JnL3dpa2kvVmlydGlvX09u X1hlbgpBbmQgZXZlbiBtb3JlLCB0aGF0IHdhcyBhbHNvIHJhaXNlZCBhdCBMaW51eCBQbHVtYmVy cwpDb25mZXJlbmNlIDIwMTMgWzFdLiBCdXQgc3RpbGwsIHRoZXJlIGlzIG5vIGltcGxlbWVudGF0 aW9uCmF2YWlsYWJsZQo+PiA0LiBNb3N0IG9mIHRoZSBQViBkcml2ZXJzIGEgZ3Vlc3QgdXNlcyBh dCB0aGUgbW9tZW50IGFyZSBYZW4gUFYgZHJpdmVycywKPj4gZS5nLiBuZXQsCj4+IGJsb2NrLCBj b25zb2xlLCBzbyBvbmx5IHZpcnRpby1ncHUgd2lsbCByZXF1aXJlIFFFTVUgdG8gcnVuLgo+IFlv dSBhcmUgbm90IGZvcmNlZCB0byB1c2UgcWVtdSwgeW91IGNhbiBjZXJ0YWlubHkgY3JlYXRlIGFu IGFsdGVybmF0aXZlCj4gaG9zdCBzaWRlIGltcGxlbWVudGF0aW9uIChhbmQgc3RpbGwgdXNlIG9u IHRoZSBleGlzdGluZyB2aXJ0aW8gZ3Vlc3QKPiBkcml2ZXJzKS4KWWVzLCB0aGlzIGlzIHRydWUu IFdlIGFsc28gZGlzY3Vzc2VkIHZpcnRpbyB3aXRoIFhlbgpjb21tdW5pdHksIFN0ZWZhbm8gU3Rh YmVsbGluaSBzYXlzOgoidGhlIGlzc3VlcyB3aXRoIHZpcnRpbyBhcmUgKGluIG9yZGVyIG9mIHNl cmlvdXNuZXNzKToKCjEpIHZpcnRpbyBhc3N1bWVzIHRoYXQgdGhlIGJhY2tlbmQgaXMgYWJsZSB0 byBtYXAgYW55IHBhZ2UgaW4gbWVtb3J5CkluIG90aGVyIHdvcmRzLCBpdCBpcyBub3QgcG9zc2li bGUgdG8gZG8gZHJpdmVyIGRvbWFpbnMgd2l0aCB2aXJ0aW8KCjIpIHZpcnRpbyBkb2Vzbid0IHdv cmsgd2l0aCBQViBndWVzdHMsIG9ubHkgSFZNIChJIHRoaW5rIFBWSCB3b3VsZCBoYXZlCiDCoCB0 aGUgc2FtZSBpc3N1ZSkKVmlydGlvIGRvZXMgc3luY2hyb25vdXMgSU8gZW11bGF0aW9uLiBRRU1V IGZvciBQViBndWVzdHMgaXMgbm90IGNhcGFibGUKb2YgaGFuZGxpbmcgc3luY2hyb25vdXMgSU8g cmVxdWVzdHMuIFRoZSBpbmZyYXRydWN0dXJlIGlzIGp1c3Qgbm90CnRoZXJlLgoKMykgdmlydGlv IHBlcmZvcm1hbmNlIGlzIHBvb3Igd2l0aCBYZW4KVGhlcmUgYXJlIG11bHRpcGxlIHJlYXNvbnMg Zm9yIHRoaXMsIGJ1dCB0aGUgbWFpbiBvbmUgaXMgdGhhdCB0aGUKYmFja2VuZHMgYXJlIGluIFFF TVUsIHJ1bm5pbmcgaW4gRG9tMC4gVGhleSBiZWNvbWUgdGhlIGJvdHRsZW5lY2sKcXVpY2tseS4K Igo+IFdoZW5ldmVyIHdyaXRpbmcgYSB4ZW5idXMgaW1wbGVtZW50YXRpb24gZm9yIGJvdGggZ3Vl c3QgYW5kIGhvc3Qgb3IKPiB3cml0aW5nIGEgdmlydGlvIGltcGxlbWVudGF0aW9uIGZvciB0aGUg aG9zdCBvbmx5IGlzIGJldHRlciAtLSBkdW5uby4KPiBUaGUgdmlydGlvIHBhdGggb2J2aW91c2x5 IG5lZWRzIHNvbWUgaW5mcmFzdHJ1Y3R1cmUgd29yayBmb3IgdmlydGlvCj4gc3VwcG9ydCBpbiBY ZW4sIHdoaWNoIG1heSBwYXkgb2ZmIGxvbmcgdGVybS4gIFlvdXIgY2FsbC4KV2VsbCwgSSBkbyBh Z3JlZSB0aGF0IGxvbmcgdGVybSB2aXJ0aW8gbWlnaHQgYmUgYSBiZXR0ZXIgY2hvaWNlLgpCdXQg YXQgdGhlIG1vbWVudCBJIHN0aWxsIHRlbmQgdG8gaGF2ZSBhIGRlZGljYXRlZCBYZW4gUFYgRFJN CmltcGxlbWVudGF0aW9uLgoKVGhhdCBiZWluZyBzYWlkLCBJIHdvdWxkIGtpbmRseSBhc2sgRFJJ IGNvbW11bml0eSB0byByZXZpZXcKdGhlIGRyaXZlciBhbmQgY29uc2lkZXIgaXQgZm9yIGluY2x1 c2lvbi4KPiBjaGVlcnMsCj4gICAgR2VyZAo+ClRoYW5rIHlvdSwKT2xla3NhbmRyIEFuZHJ1c2hj aGVua28KClsxXSBodHRwczovL3d3dy55b3V0dWJlLmNvbS93YXRjaD92PUZjVkRIQlFJbnhBCl9f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fCmRyaS1kZXZlbCBt YWlsaW5nIGxpc3QKZHJpLWRldmVsQGxpc3RzLmZyZWVkZXNrdG9wLm9yZwpodHRwczovL2xpc3Rz LmZyZWVkZXNrdG9wLm9yZy9tYWlsbWFuL2xpc3RpbmZvL2RyaS1kZXZlbAo=