From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Subject: Re: [PATCH v4 0/6] virtio core DMA API conversion Date: Wed, 11 Nov 2015 06:37:38 +1100 Message-ID: <1447184258.31884.91.camel@kernel.crashing.org> References: <20151109133624-mutt-send-email-mst@redhat.com> <1447109937.31884.42.camel@kernel.crashing.org> <1447121076.31884.61.camel@kernel.crashing.org> <1447133316.31884.67.camel@kernel.crashing.org> <1447151874.31884.82.camel@kernel.crashing.org> <20151110142633-mutt-send-email-mst@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: In-Reply-To: <20151110142633-mutt-send-email-mst@redhat.com> 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 List-Archive: List-Post: To: "Michael S. Tsirkin" Cc: Joerg Roedel , KVM , linux-s390 , Sebastian Ott , "linux-kernel@vger.kernel.org" , Andy Lutomirski , Christian Borntraeger , Christoph Hellwig , Andy Lutomirski , sparclinux@vger.kernel.org, Paolo Bonzini , Linux Virtualization , David Woodhouse , "David S. Miller" , Martin Schwidefsky List-ID: T24gVHVlLCAyMDE1LTExLTEwIGF0IDE0OjQzICswMjAwLCBNaWNoYWVsIFMuIFRzaXJraW4gd3Jv dGU6Cj4gQnV0IG5vdCB2aXJ0aW8tcGNpIEkgdGhpbmsgLSB0aGF0J3MgYnJva2VuIGZvciB0aGF0 IHVzZWNhc2Ugc2luY2Ugd2UgdXNlCj4gd2Vha2VyIGJhcnJpZXJzIHRoYW4gcmVxdWlyZWQgZm9y IHJlYWwgSU8sIGFzIHRoZXNlIGhhdmUgbWVhc3VyZWFibGUKPiBvdmVyaGVhZC7CoCBXZSBjb3Vs ZCBoYXZlIGEgZmVhdHVyZSAiaXMgYSByZWFsIFBDSSBkZXZpY2UiLAo+IHRoYXQncyBjb21wbGV0 ZWx5IHJlYXNvbmFibGUuCgpEbyB3ZSB1c2Ugd2Vha2VyIGJhcnJpZXJzIG9uIHRoZSBMaW51eCBk cml2ZXIgc2lkZSA/IEkgZGlkbid0IHRoaW5rIHNvCi4uLsKgCgpDaGVlcnMsCkJlbi4KCl9fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fClZpcnR1YWxpemF0aW9u IG1haWxpbmcgbGlzdApWaXJ0dWFsaXphdGlvbkBsaXN0cy5saW51eC1mb3VuZGF0aW9uLm9yZwpo dHRwczovL2xpc3RzLmxpbnV4Zm91bmRhdGlvbi5vcmcvbWFpbG1hbi9saXN0aW5mby92aXJ0dWFs aXphdGlvbg== From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Date: Tue, 10 Nov 2015 19:37:38 +0000 Subject: Re: [PATCH v4 0/6] virtio core DMA API conversion Message-Id: <1447184258.31884.91.camel@kernel.crashing.org> List-Id: References: <20151109133624-mutt-send-email-mst@redhat.com> <1447109937.31884.42.camel@kernel.crashing.org> <1447121076.31884.61.camel@kernel.crashing.org> <1447133316.31884.67.camel@kernel.crashing.org> <1447151874.31884.82.camel@kernel.crashing.org> <20151110142633-mutt-send-email-mst@redhat.com> In-Reply-To: <20151110142633-mutt-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit To: "Michael S. Tsirkin" Cc: Joerg Roedel , KVM , linux-s390 , Sebastian Ott , "linux-kernel@vger.kernel.org" , Andy Lutomirski , Christian Borntraeger , Christoph Hellwig , Andy Lutomirski , sparclinux@vger.kernel.org, Paolo Bonzini , Linux Virtualization , David Woodhouse , "David S. Miller" , Martin Schwidefsky On Tue, 2015-11-10 at 14:43 +0200, Michael S. Tsirkin wrote: > But not virtio-pci I think - that's broken for that usecase since we use > weaker barriers than required for real IO, as these have measureable > overhead.  We could have a feature "is a real PCI device", > that's completely reasonable. Do we use weaker barriers on the Linux driver side ? I didn't think so ...  Cheers, Ben. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752141AbbKJUbW (ORCPT ); Tue, 10 Nov 2015 15:31:22 -0500 Received: from gate.crashing.org ([63.228.1.57]:50557 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751618AbbKJUbU (ORCPT ); Tue, 10 Nov 2015 15:31:20 -0500 Message-ID: <1447184258.31884.91.camel@kernel.crashing.org> Subject: Re: [PATCH v4 0/6] virtio core DMA API conversion From: Benjamin Herrenschmidt To: "Michael S. Tsirkin" Cc: Andy Lutomirski , Andy Lutomirski , David Woodhouse , "linux-kernel@vger.kernel.org" , "David S. Miller" , sparclinux@vger.kernel.org, Joerg Roedel , Christian Borntraeger , Cornelia Huck , Sebastian Ott , Paolo Bonzini , Christoph Hellwig , KVM , Martin Schwidefsky , linux-s390 , Linux Virtualization Date: Wed, 11 Nov 2015 06:37:38 +1100 In-Reply-To: <20151110142633-mutt-send-email-mst@redhat.com> References: <20151109133624-mutt-send-email-mst@redhat.com> <1447109937.31884.42.camel@kernel.crashing.org> <1447121076.31884.61.camel@kernel.crashing.org> <1447133316.31884.67.camel@kernel.crashing.org> <1447151874.31884.82.camel@kernel.crashing.org> <20151110142633-mutt-send-email-mst@redhat.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.18.1 (3.18.1-1.fc23) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2015-11-10 at 14:43 +0200, Michael S. Tsirkin wrote: > But not virtio-pci I think - that's broken for that usecase since we use > weaker barriers than required for real IO, as these have measureable > overhead.  We could have a feature "is a real PCI device", > that's completely reasonable. Do we use weaker barriers on the Linux driver side ? I didn't think so ...  Cheers, Ben.