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Tsirkin" To: "Wang, Wei W" Subject: Re: [RFC] hypercall-vsock: add a new vsock transport Message-ID: <20211110054121-mutt-send-email-mst@kernel.org> References: <71d7b0463629471e9d4887d7fcef1d8d@intel.com> MIME-Version: 1.0 In-Reply-To: <71d7b0463629471e9d4887d7fcef1d8d@intel.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: "Yamahata, Isaku" , "linux-kernel@vger.kernel.org" , "virtualization@lists.linux-foundation.org" , Stefan Hajnoczi , Paolo Bonzini , "Kleen, Andi" , "kuba@kernel.org" , "davem@davemloft.net" X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" T24gV2VkLCBOb3YgMTAsIDIwMjEgYXQgMDc6MTI6MzZBTSArMDAwMCwgV2FuZywgV2VpIFcgd3Jv dGU6Cj4gSGksCj4gCj4gIAo+IAo+IFdlIHBsYW4gdG8gYWRkIGEgbmV3IHZzb2NrIHRyYW5zcG9y dCBiYXNlZCBvbiBoeXBlcmNhbGwgKGUuZy4gdm1jYWxsIG9uIEludGVsCj4gQ1BVcykuCj4gCj4g SXQgdHJhbnNwb3J0cyBBRl9WU09DSyBwYWNrZXRzIGJldHdlZW4gdGhlIGd1ZXN0IGFuZCBob3N0 LCB3aGljaCBpcyBzaW1pbGFyIHRvCj4gCj4gdmlydGlvLXZzb2NrLCB2bWNpLXZzb2NrIGFuZCBo eXBlcnYtdnNvY2suCj4gCj4gIAo+IAo+IENvbXBhcmVkIHRvIHRoZSBhYm92ZSBsaXN0ZWQgdnNv Y2sgdHJhbnNwb3J0cyB3aGljaCBhcmUgZGVzaWduZWQgZm9yIGhpZ2gKPiBwZXJmb3JtYW5jZSwK PiAKPiB0aGUgbWFpbiBhZHZhbnRhZ2VzIG9mIGh5cGVyY2FsbC12c29jayBhcmU6Cj4gCj4gMSkg ICAgICAgSXQgaXMgVk1NIGFnbm9zdGljLiBGb3IgZXhhbXBsZSwgb25lIGd1ZXN0IHdvcmtpbmcg b24gaHlwZXJjYWxsLXZzb2NrCj4gY2FuIHJ1biBvbgo+IAo+IGVpdGhlciBLVk0sIEh5cGVydiwg b3IgVk13YXJlLgoKaHlwZXJjYWxscyBhcmUgZnVuZGFtZW50YWxseSBoeXBlcnZpc29yIGRlcGVu ZGVudCB0aG91Z2guCkFzc3VtaW5nIHlvdSBjYW4gY2FydmUgdXAgYSBoeXBlcnZpc29yIGluZGVw ZW5kZW50IGh5cGVyY2FsbCwKdXNpbmcgaXQgZm9yIHNvbWV0aGluZyBhcyBtdW5kYW5lIGFuZCBz cGVjaWZpYyBhcyB2c29jayBmb3IgVERYCnNlZW1zIGxpa2UgYSBodWdlIG92ZXJraWxsLiBGb3Ig ZXhhbXBsZSwgdmlydGlvIGNvdWxkIGJlbmVmaXQgZnJvbQpmYXN0ZXIgdm1leGl0cyB0aGF0IGh5 cGVyY2FsbHMgZ2l2ZSB5b3UgZm9yIHNpZ25hbGxpbmcuCkhvdyBhYm91dCBhIGNvbWJpbmF0aW9u IG9mIHZpcnRpby1tbWlvIGFuZCBoeXBlcmNhbGxzIGZvciBmYXN0LXBhdGgKc2lnbmFsbGluZyB0 aGVuPwoKPiAyKSAgICAgICBJdCBpcyBzaW1wbGVyLiBJdCBkb2VzbuKAmXQgcmVseSBvbiBhbnkg Y29tcGxleCBidXMgZW51bWVyYXRpb24KPiAKPiAoZS5nLiB2aXJ0aW8tcGNpIGJhc2VkIHZzb2Nr IGRldmljZSBtYXkgbmVlZCB0aGUgd2hvbGUgaW1wbGVtZW50YXRpb24gb2YgUENJKS4KPiAKCk5l eHQgdGhpbmcgcGVvcGxlIHdpbGwgdHJ5IHRvIGRvIGlzIGltcGxlbWVudCBhIGJ1bmNoIG9mIG90 aGVyIGRldmljZSBvbgp0b3Agb2YgaXQuICB2aXJ0aW8gdXNlZCBwY2kgc2ltcGx5IGJlY2F1c2Ug ZXZlcnlvbmUgaW1wbGVtZW50cyBwY2kuICBBbmQKdGhlIHJlYXNvbiBmb3IgKnRoYXQqIGlzIGJl Y2F1c2UgaW1wbGVtZW50aW5nIGEgYmFzaWMgcGNpIGJ1cyBpcyBkZWFkCnNpbXBsZSwgd2hvbGUg b2YgcGNpLmMgaW4gcWVtdSBpcyA8MzAwMCBMT0MuCgo+IAo+IEFuIGV4YW1wbGUgdXNhZ2UgaXMg dGhlIGNvbW11bmljYXRpb24gYmV0d2VlbiBNaWdURCBhbmQgaG9zdCAoUGFnZSA4IGF0Cj4gCj4g aHR0cHM6Ly9zdGF0aWMuc2NoZWQuY29tL2hvc3RlZF9maWxlcy9rdm1mb3J1bTIwMjEvZWYvCj4g VERYJTIwTGl2ZSUyME1pZ3JhdGlvbl9XZWklMjBXYW5nLnBkZikuCj4gCj4gTWlnVEQgY29tbXVu aWNhdGVzIHRvIGhvc3QgdG8gYXNzaXN0IHRoZSBtaWdyYXRpb24gb2YgdGhlIHRhcmdldCAodXNl cikgVEQuCj4gCj4gTWlnVEQgaXMgcGFydCBvZiB0aGUgVENCLCBzbyBpdHMgaW1wbGVtZW50YXRp b24gaXMgZXhwZWN0ZWQgdG8gYmUgYXMgc2ltcGxlIGFzCj4gcG9zc2libGUKPiAKPiAoZS5nLiBi YXJlIG1lbnRhbCBpbXBsZW1lbnRhdGlvbiB3aXRob3V0IE9TLCBubyBQQ0kgZHJpdmVyIHN1cHBv cnQpLgo+IAo+ICAKClRyeSB0byBsaXN0IGRyYXdiYWNrcz8gRm9yIGV4YW1wbGUsIHBhc3N0aHJv dWdoIGZvciBuZXN0ZWQgdmlydAppc24ndCBwb3NzaWJsZSB1bmxpa2UgcGNpLCBuZWl0aGVyIGFy ZSBoYXJkd2FyZSBpbXBsZW1lbnRhdGlvbnMuCgoKPiBMb29raW5nIGZvcndhcmQgdG8geW91ciBm ZWVkYmFja3MuCj4gCj4gIAo+IAo+IFRoYW5rcywKPiAKPiBXZWkKPiAKCl9fX19fX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fClZpcnR1YWxpemF0aW9uIG1haWxpbmcg bGlzdApWaXJ0dWFsaXphdGlvbkBsaXN0cy5saW51eC1mb3VuZGF0aW9uLm9yZwpodHRwczovL2xp c3RzLmxpbnV4Zm91bmRhdGlvbi5vcmcvbWFpbG1hbi9saXN0aW5mby92aXJ0dWFsaXphdGlvbg== From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 17BEEC433F5 for ; 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Wed, 10 Nov 2021 02:50:08 -0800 (PST) X-Google-Smtp-Source: ABdhPJxeT1zDnGo3NXhEoFr9pMWu5dF4RmCmR5eGCjSrmvQE09ovJLCuK0RgjGQCXT9xOJaoYx2OdQ== X-Received: by 2002:a05:6402:50d4:: with SMTP id h20mr20019833edb.80.1636541408669; Wed, 10 Nov 2021 02:50:08 -0800 (PST) Received: from redhat.com ([2.55.133.41]) by smtp.gmail.com with ESMTPSA id cw20sm10928049ejc.32.2021.11.10.02.50.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Nov 2021 02:50:07 -0800 (PST) Date: Wed, 10 Nov 2021 05:50:04 -0500 From: "Michael S. Tsirkin" To: "Wang, Wei W" Cc: "sgarzare@redhat.com" , "davem@davemloft.net" , "kuba@kernel.org" , Stefan Hajnoczi , Paolo Bonzini , "kys@microsoft.com" , "linux-kernel@vger.kernel.org" , "virtualization@lists.linux-foundation.org" , "Yamahata, Isaku" , "Nakajima, Jun" , "Kleen, Andi" Subject: Re: [RFC] hypercall-vsock: add a new vsock transport Message-ID: <20211110054121-mutt-send-email-mst@kernel.org> References: <71d7b0463629471e9d4887d7fcef1d8d@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <71d7b0463629471e9d4887d7fcef1d8d@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 10, 2021 at 07:12:36AM +0000, Wang, Wei W wrote: > Hi, > > > > We plan to add a new vsock transport based on hypercall (e.g. vmcall on Intel > CPUs). > > It transports AF_VSOCK packets between the guest and host, which is similar to > > virtio-vsock, vmci-vsock and hyperv-vsock. > > > > Compared to the above listed vsock transports which are designed for high > performance, > > the main advantages of hypercall-vsock are: > > 1) It is VMM agnostic. For example, one guest working on hypercall-vsock > can run on > > either KVM, Hyperv, or VMware. hypercalls are fundamentally hypervisor dependent though. Assuming you can carve up a hypervisor independent hypercall, using it for something as mundane and specific as vsock for TDX seems like a huge overkill. For example, virtio could benefit from faster vmexits that hypercalls give you for signalling. How about a combination of virtio-mmio and hypercalls for fast-path signalling then? > 2) It is simpler. It doesn’t rely on any complex bus enumeration > > (e.g. virtio-pci based vsock device may need the whole implementation of PCI). > Next thing people will try to do is implement a bunch of other device on top of it. virtio used pci simply because everyone implements pci. And the reason for *that* is because implementing a basic pci bus is dead simple, whole of pci.c in qemu is <3000 LOC. > > An example usage is the communication between MigTD and host (Page 8 at > > https://static.sched.com/hosted_files/kvmforum2021/ef/ > TDX%20Live%20Migration_Wei%20Wang.pdf). > > MigTD communicates to host to assist the migration of the target (user) TD. > > MigTD is part of the TCB, so its implementation is expected to be as simple as > possible > > (e.g. bare mental implementation without OS, no PCI driver support). > > Try to list drawbacks? For example, passthrough for nested virt isn't possible unlike pci, neither are hardware implementations. > Looking forward to your feedbacks. > > > > Thanks, > > Wei >