From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: virtio-dev-return-4481-cohuck=redhat.com@lists.oasis-open.org Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [66.179.20.138]) by lists.oasis-open.org (Postfix) with ESMTP id 3D0C31CB80F0 for ; Thu, 21 Jun 2018 19:30:55 -0700 (PDT) Date: Fri, 22 Jun 2018 05:30:43 +0300 From: "Michael S. Tsirkin" Message-ID: <20180622052717-mutt-send-email-mst@kernel.org> References: <1525734594-11134-1-git-send-email-sridhar.samudrala@intel.com> <20180605152344-mutt-send-email-mst@kernel.org> <20180612144743-mutt-send-email-mst@kernel.org> <5718de66-74c9-1362-a87b-2eba02475b48@redhat.com> <20180621211359-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Subject: Re: [virtio-dev] Re: [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net To: Siwei Liu Cc: Jason Wang , "Samudrala, Sridhar" , virtualization@lists.linux-foundation.org, virtio-dev@lists.oasis-open.org, "Brandeburg, Jesse" , Alexander Duyck , qemu-devel@nongnu.org List-ID: On Thu, Jun 21, 2018 at 06:07:18PM -0700, Siwei Liu wrote: > On Thu, Jun 21, 2018 at 11:14 AM, Michael S. Tsirkin wrote: > > On Wed, Jun 13, 2018 at 01:40:59PM +0800, Jason Wang wrote: > >> > >> > >> On 2018年06月13日 12:24, Samudrala, Sridhar wrote: > >> > On 6/12/2018 7:38 PM, Jason Wang wrote: > >> > > > >> > > > >> > > On 2018年06月12日 19:54, Michael S. Tsirkin wrote: > >> > > > On Wed, Jun 06, 2018 at 10:29:03AM +0800, Jason Wang wrote: > >> > > > > > >> > > > > On 2018年06月05日 20:33, Michael S. Tsirkin wrote: > >> > > > > > I don't think this is sufficient. > >> > > > > > > >> > > > > > If both primary and standby devices are present, a > >> > > > > > legacy guest without > >> > > > > > support for the feature might see two devices with same mac and get > >> > > > > > confused. > >> > > > > > > >> > > > > > I think that we should only make primary visible after > >> > > > > > guest acked the > >> > > > > > backup feature bit. > >> > > > > I think we want exactly the reverse? E.g fail the > >> > > > > negotiation when guest > >> > > > > does not ack backup feature. > >> > > > > > >> > > > > Otherwise legacy guest won't even have the chance to see > >> > > > > primary device in > >> > > > > the guest. > >> > > > That's by design. > >> > > > >> > > So management needs to know the capability of guest to set the > >> > > backup feature. This looks a chicken or egg problem to me. > >> > > >> > I don't think so. If the tenant requests 'accelerated datapath feature', > >> > the management > >> > will set 'standby' feature bit on virtio-net interface and if the guest > >> > virtio-net driver > >> > supports this feature, then the tenant VM will get that capability via a > >> > hot-plugged > >> > primary device. > >> > >> Ok, I thought exactly the reverse because of the commit title is "enable > >> virtio_net to act as a standby for a passthru device". But re-read the > >> commit log content, I understand the case a little bit. Btw, VF is not > >> necessarily faster than virtio-net, especially consider virtio-net may have > >> a lot of queues. > > > > Don't do that then, right? > > I don't understand. Where did the standby feature come to imply the > "accelerated datapath" thing? > Isn't failover/standby a generic high > availblity term, rather than marry it to the concept of device model > specifics? Do we expect scsi to work exactly the same way with > "accelerated datapath"? That's not what I said. The semantics are that the primary is always used if present in preference to standby. Jason said virtio net is sometimes preferable. If that's the case don't make it a standby. More advanced use-cases do exist and e.g. Alexander Duyck suggested using a switch-dev. failover isn't it though. -- MST --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [virtio-dev] Re: [PATCH] qemu: Introduce VIRTIO_NET_F_STANDBY feature bit to virtio_net Date: Fri, 22 Jun 2018 05:30:43 +0300 Message-ID: <20180622052717-mutt-send-email-mst@kernel.org> References: <1525734594-11134-1-git-send-email-sridhar.samudrala@intel.com> <20180605152344-mutt-send-email-mst@kernel.org> <20180612144743-mutt-send-email-mst@kernel.org> <5718de66-74c9-1362-a87b-2eba02475b48@redhat.com> <20180621211359-mutt-send-email-mst@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Siwei Liu Cc: Alexander Duyck , virtio-dev@lists.oasis-open.org, qemu-devel@nongnu.org, "Samudrala, Sridhar" , virtualization@lists.linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org T24gVGh1LCBKdW4gMjEsIDIwMTggYXQgMDY6MDc6MThQTSAtMDcwMCwgU2l3ZWkgTGl1IHdyb3Rl Ogo+IE9uIFRodSwgSnVuIDIxLCAyMDE4IGF0IDExOjE0IEFNLCBNaWNoYWVsIFMuIFRzaXJraW4g PG1zdEByZWRoYXQuY29tPiB3cm90ZToKPiA+IE9uIFdlZCwgSnVuIDEzLCAyMDE4IGF0IDAxOjQw OjU5UE0gKzA4MDAsIEphc29uIFdhbmcgd3JvdGU6Cj4gPj4KPiA+Pgo+ID4+IE9uIDIwMTjlubQw NuaciDEz5pelIDEyOjI0LCBTYW11ZHJhbGEsIFNyaWRoYXIgd3JvdGU6Cj4gPj4gPiBPbiA2LzEy LzIwMTggNzozOCBQTSwgSmFzb24gV2FuZyB3cm90ZToKPiA+PiA+ID4KPiA+PiA+ID4KPiA+PiA+ ID4gT24gMjAxOOW5tDA25pyIMTLml6UgMTk6NTQsIE1pY2hhZWwgUy4gVHNpcmtpbiB3cm90ZToK PiA+PiA+ID4gPiBPbiBXZWQsIEp1biAwNiwgMjAxOCBhdCAxMDoyOTowM0FNICswODAwLCBKYXNv biBXYW5nIHdyb3RlOgo+ID4+ID4gPiA+ID4KPiA+PiA+ID4gPiA+IE9uIDIwMTjlubQwNuaciDA1 5pelIDIwOjMzLCBNaWNoYWVsIFMuIFRzaXJraW4gd3JvdGU6Cj4gPj4gPiA+ID4gPiA+IEkgZG9u J3QgdGhpbmsgdGhpcyBpcyBzdWZmaWNpZW50Lgo+ID4+ID4gPiA+ID4gPgo+ID4+ID4gPiA+ID4g PiBJZiBib3RoIHByaW1hcnkgYW5kIHN0YW5kYnkgZGV2aWNlcyBhcmUgcHJlc2VudCwgYQo+ID4+ ID4gPiA+ID4gPiBsZWdhY3kgZ3Vlc3Qgd2l0aG91dAo+ID4+ID4gPiA+ID4gPiBzdXBwb3J0IGZv ciB0aGUgZmVhdHVyZSBtaWdodCBzZWUgdHdvIGRldmljZXMgd2l0aCBzYW1lIG1hYyBhbmQgZ2V0 Cj4gPj4gPiA+ID4gPiA+IGNvbmZ1c2VkLgo+ID4+ID4gPiA+ID4gPgo+ID4+ID4gPiA+ID4gPiBJ IHRoaW5rIHRoYXQgd2Ugc2hvdWxkIG9ubHkgbWFrZSBwcmltYXJ5IHZpc2libGUgYWZ0ZXIKPiA+ PiA+ID4gPiA+ID4gZ3Vlc3QgYWNrZWQgdGhlCj4gPj4gPiA+ID4gPiA+IGJhY2t1cCBmZWF0dXJl IGJpdC4KPiA+PiA+ID4gPiA+IEkgdGhpbmsgd2Ugd2FudCBleGFjdGx5IHRoZSByZXZlcnNlPyBF LmcgZmFpbCB0aGUKPiA+PiA+ID4gPiA+IG5lZ290aWF0aW9uIHdoZW4gZ3Vlc3QKPiA+PiA+ID4g PiA+IGRvZXMgbm90IGFjayBiYWNrdXAgZmVhdHVyZS4KPiA+PiA+ID4gPiA+Cj4gPj4gPiA+ID4g PiBPdGhlcndpc2UgbGVnYWN5IGd1ZXN0IHdvbid0IGV2ZW4gaGF2ZSB0aGUgY2hhbmNlIHRvIHNl ZQo+ID4+ID4gPiA+ID4gcHJpbWFyeSBkZXZpY2UgaW4KPiA+PiA+ID4gPiA+IHRoZSBndWVzdC4K PiA+PiA+ID4gPiBUaGF0J3MgYnkgZGVzaWduLgo+ID4+ID4gPgo+ID4+ID4gPiBTbyBtYW5hZ2Vt ZW50IG5lZWRzIHRvIGtub3cgdGhlIGNhcGFiaWxpdHkgb2YgZ3Vlc3QgdG8gc2V0IHRoZQo+ID4+ ID4gPiBiYWNrdXAgZmVhdHVyZS4gVGhpcyBsb29rcyBhIGNoaWNrZW4gb3IgZWdnIHByb2JsZW0g dG8gbWUuCj4gPj4gPgo+ID4+ID4gSSBkb24ndCB0aGluayBzby4gSWYgdGhlIHRlbmFudCByZXF1 ZXN0cyAnYWNjZWxlcmF0ZWQgZGF0YXBhdGggZmVhdHVyZScsCj4gPj4gPiB0aGUgbWFuYWdlbWVu dAo+ID4+ID4gd2lsbCBzZXQgJ3N0YW5kYnknIGZlYXR1cmUgYml0IG9uIHZpcnRpby1uZXQgaW50 ZXJmYWNlIGFuZCBpZiB0aGUgZ3Vlc3QKPiA+PiA+IHZpcnRpby1uZXQgZHJpdmVyCj4gPj4gPiBz dXBwb3J0cyB0aGlzIGZlYXR1cmUsIHRoZW4gdGhlIHRlbmFudCBWTSB3aWxsIGdldCB0aGF0IGNh cGFiaWxpdHkgdmlhIGEKPiA+PiA+IGhvdC1wbHVnZ2VkCj4gPj4gPiBwcmltYXJ5IGRldmljZS4K PiA+Pgo+ID4+IE9rLCBJIHRob3VnaHQgZXhhY3RseSB0aGUgcmV2ZXJzZSBiZWNhdXNlIG9mIHRo ZSBjb21taXQgdGl0bGUgaXMgImVuYWJsZQo+ID4+IHZpcnRpb19uZXQgdG8gYWN0IGFzIGEgc3Rh bmRieSBmb3IgYSBwYXNzdGhydSBkZXZpY2UiLiBCdXQgcmUtcmVhZCB0aGUKPiA+PiBjb21taXQg bG9nIGNvbnRlbnQsIEkgdW5kZXJzdGFuZCB0aGUgY2FzZSBhIGxpdHRsZSBiaXQuIEJ0dywgVkYg aXMgbm90Cj4gPj4gbmVjZXNzYXJpbHkgZmFzdGVyIHRoYW4gdmlydGlvLW5ldCwgZXNwZWNpYWxs eSBjb25zaWRlciB2aXJ0aW8tbmV0IG1heSBoYXZlCj4gPj4gYSBsb3Qgb2YgcXVldWVzLgo+ID4K PiA+IERvbid0IGRvIHRoYXQgdGhlbiwgcmlnaHQ/Cj4gCj4gSSBkb24ndCB1bmRlcnN0YW5kLiBX aGVyZSBkaWQgdGhlIHN0YW5kYnkgZmVhdHVyZSBjb21lIHRvIGltcGx5IHRoZQo+ICJhY2NlbGVy YXRlZCBkYXRhcGF0aCIgdGhpbmc/Cj4gSXNuJ3QgZmFpbG92ZXIvc3RhbmRieSBhIGdlbmVyaWMg aGlnaAo+IGF2YWlsYmxpdHkgdGVybSwgcmF0aGVyIHRoYW4gbWFycnkgaXQgdG8gdGhlIGNvbmNl cHQgb2YgZGV2aWNlIG1vZGVsCj4gc3BlY2lmaWNzPyBEbyB3ZSBleHBlY3Qgc2NzaSB0byB3b3Jr IGV4YWN0bHkgdGhlIHNhbWUgd2F5IHdpdGgKPiAiYWNjZWxlcmF0ZWQgZGF0YXBhdGgiPwoKVGhh dCdzIG5vdCB3aGF0IEkgc2FpZC4KVGhlIHNlbWFudGljcyBhcmUgdGhhdCB0aGUgcHJpbWFyeSBp cyBhbHdheXMgdXNlZCBpZiBwcmVzZW50IGluCnByZWZlcmVuY2UgdG8gc3RhbmRieS4KSmFzb24g c2FpZCB2aXJ0aW8gbmV0IGlzIHNvbWV0aW1lcyBwcmVmZXJhYmxlLgpJZiB0aGF0J3MgdGhlIGNh c2UgZG9uJ3QgbWFrZSBpdCBhIHN0YW5kYnkuCgpNb3JlIGFkdmFuY2VkIHVzZS1jYXNlcyBkbyBl eGlzdCBhbmQgZS5nLiBBbGV4YW5kZXIgRHV5Y2sKc3VnZ2VzdGVkIHVzaW5nIGEgc3dpdGNoLWRl di4gZmFpbG92ZXIgaXNuJ3QgaXQgdGhvdWdoLgoKLS0gCk1TVApfX19fX19fX19fX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fXwpWaXJ0dWFsaXphdGlvbiBtYWlsaW5nIGxpc3QK VmlydHVhbGl6YXRpb25AbGlzdHMubGludXgtZm91bmRhdGlvbi5vcmcKaHR0cHM6Ly9saXN0cy5s aW51eGZvdW5kYXRpb24ub3JnL21haWxtYW4vbGlzdGluZm8vdmlydHVhbGl6YXRpb24=