From: "Raslan, KarimAllah" <karahmed@amazon.de> To: David Vrabel <david.vrabel@citrix.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org> Cc: Juergen Gross <jgross@suse.com>, Ross Lagerwall <ross.lagerwall@citrix.com>, "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>, "x86@kernel.org" <x86@kernel.org>, "Paul Gortmaker" <paul.gortmaker@windriver.com>, Julien Grall <julien.grall@citrix.com>, Vitaly Kuznetsov <vkuznets@redhat.com>, "Ingo Molnar" <mingo@redhat.com>, "Liguori, Anthony" <aliguori@amazon.com>, "H. Peter Anvin" <hpa@zytor.com>, Bjorn Helgaas <bhelgaas@google.com>, "Boris Ostrovsky" <boris.ostrovsky@oracle.com>, Thomas Gleixner <tglx@linutronix.de>, Stefano Stabellini <stefano.stabellini@eu.citrix.com> Subject: Re: [Xen-devel] [PATCH] xen: Remove event channel notification through Xen PCI platform device Date: Mon, 10 Apr 2017 12:28:38 +0000 [thread overview] Message-ID: <5E59C7DE-9640-4D97-A633-BFFDC4BF1352@amazon.de> (raw) In-Reply-To: <57EE7AB7.4020405@citrix.com> Unfortunately, this commit is potentially a candidate for reverting. After a lengthy qualification I realized that there is a function called: "xen_strict_xenbus_quirk()" that is being called in the offending path that short-circuits the offending code! So at the moment any domU kernel with this commit will not boot on any Xen version < 4.0! So nobody with Xen < 4.0 was complaining not because nobody is using it but rather because there is a short-circuit in the code that avoids hitting the offending code in the first place! So the original assumption that the code is dead might no be 100% correct! So even though the code for INTx is broken for any Xen > 4.0, the right thing to do now is to actually fix the INTx properly and completely revert this commit (actually now also commit da72ff5bfcb0 needs to be reverted to cleanly revert this commit) to avoid any potential regression. David, Does this make sense to you? I will send a patch to fix INTx shortly as well. On 9/30/16, 4:46 PM, "David Vrabel" <david.vrabel@citrix.com> wrote: On 26/08/16 22:55, KarimAllah Ahmed wrote: > Ever since commit 254d1a3f02eb ("xen/pv-on-hvm kexec: shutdown watches > from old kernel") using the INTx interrupt from Xen PCI platform device for > event channel notification would just lockup the guest during bootup. > postcore_initcall now calls xs_reset_watches which will eventually try to read > a value from XenStore and will get stuck on read_reply at XenBus forever since > the platform driver is not probed yet and its INTx interrupt handler is not > registered yet. That means that the guest can not be notified at this moment of > any pending event channels and none of the per-event handlers will ever be > invoked (including the XenStore one) and the reply will never be picked up by > the kernel. Applied to for-linus-4.9, thanks. David Amazon Development Center Germany GmbH Berlin - Dresden - Aachen main office: Krausenstr. 38, 10117 Berlin Geschaeftsfuehrer: Dr. Ralf Herbrich, Christian Schlaeger Ust-ID: DE289237879 Eingetragen am Amtsgericht Charlottenburg HRB 149173 B
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From: "Raslan, KarimAllah" <karahmed@amazon.de> To: David Vrabel <david.vrabel@citrix.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org> Cc: Juergen Gross <jgross@suse.com>, Ross Lagerwall <ross.lagerwall@citrix.com>, "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>, "x86@kernel.org" <x86@kernel.org>, "Paul Gortmaker" <paul.gortmaker@windriver.com>, Julien Grall <julien.grall@citrix.com>, Vitaly Kuznetsov <vkuznets@redhat.com>, "Ingo Molnar" <mingo@redhat.com>, "Liguori, Anthony" <aliguori@amazon.com>, "H. Peter Anvin" <hpa@zytor.com>, Bjorn Helgaas <bhelgaas@google.com>, "Boris Ostrovsky" <boris.ostrovsky@oracle.com>, Thomas Gleixner <tglx@linutronix.de>, Stefano Stabellini <stefano.stabellini@eu.citrix.com> Subject: Re: [Xen-devel] [PATCH] xen: Remove event channel notification through Xen PCI platform device Date: Mon, 10 Apr 2017 12:28:38 +0000 [thread overview] Message-ID: <5E59C7DE-9640-4D97-A633-BFFDC4BF1352@amazon.de> (raw) In-Reply-To: <57EE7AB7.4020405@citrix.com> VW5mb3J0dW5hdGVseSwgdGhpcyBjb21taXQgaXMgcG90ZW50aWFsbHkgYSBjYW5kaWRhdGUgZm9y IHJldmVydGluZy4gQWZ0ZXIgYQ0KbGVuZ3RoeSBxdWFsaWZpY2F0aW9uIEkgcmVhbGl6ZWQgdGhh dCB0aGVyZSBpcyBhIGZ1bmN0aW9uIGNhbGxlZDoNCiJ4ZW5fc3RyaWN0X3hlbmJ1c19xdWlyaygp IiB0aGF0IGlzIGJlaW5nIGNhbGxlZCBpbiB0aGUgb2ZmZW5kaW5nIHBhdGggdGhhdA0Kc2hvcnQt Y2lyY3VpdHMgdGhlIG9mZmVuZGluZyBjb2RlIQ0KDQpTbyBhdCB0aGUgbW9tZW50IGFueSBkb21V IGtlcm5lbCB3aXRoIHRoaXMgY29tbWl0IHdpbGwgbm90IGJvb3Qgb24gYW55IFhlbg0KdmVyc2lv biA8IDQuMCEgIFNvIG5vYm9keSB3aXRoIFhlbiA8IDQuMCB3YXMgY29tcGxhaW5pbmcgbm90IGJl Y2F1c2Ugbm9ib2R5IGlzDQp1c2luZyBpdCBidXQgcmF0aGVyIGJlY2F1c2UgdGhlcmUgaXMgYSBz aG9ydC1jaXJjdWl0IGluIHRoZSBjb2RlIHRoYXQgYXZvaWRzDQpoaXR0aW5nIHRoZSBvZmZlbmRp bmcgY29kZSBpbiB0aGUgZmlyc3QgcGxhY2UhIFNvIHRoZSBvcmlnaW5hbCBhc3N1bXB0aW9uIHRo YXQNCnRoZSBjb2RlIGlzIGRlYWQgbWlnaHQgbm8gYmUgMTAwJSBjb3JyZWN0IQ0KDQpTbyBldmVu IHRob3VnaCB0aGUgY29kZSBmb3IgSU5UeCBpcyBicm9rZW4gZm9yIGFueSBYZW4gPiA0LjAsIHRo ZSByaWdodCB0aGluZw0KdG8gZG8gbm93IGlzIHRvIGFjdHVhbGx5IGZpeCB0aGUgSU5UeCBwcm9w ZXJseSBhbmQgY29tcGxldGVseSByZXZlcnQgdGhpcw0KY29tbWl0IChhY3R1YWxseSBub3cgYWxz byBjb21taXQgZGE3MmZmNWJmY2IwIG5lZWRzIHRvIGJlIHJldmVydGVkIHRvIGNsZWFubHkNCnJl dmVydCB0aGlzIGNvbW1pdCkgdG8gYXZvaWQgYW55IHBvdGVudGlhbCByZWdyZXNzaW9uLg0KDQpE YXZpZCwNCkRvZXMgdGhpcyBtYWtlIHNlbnNlIHRvIHlvdT8NCg0KSSB3aWxsIHNlbmQgYSBwYXRj aCB0byBmaXggSU5UeCBzaG9ydGx5IGFzIHdlbGwuDQoNCk9uIDkvMzAvMTYsIDQ6NDYgUE0sICJE YXZpZCBWcmFiZWwiIDxkYXZpZC52cmFiZWxAY2l0cml4LmNvbT4gd3JvdGU6DQoNCiAgICBPbiAy Ni8wOC8xNiAyMjo1NSwgS2FyaW1BbGxhaCBBaG1lZCB3cm90ZToNCiAgICA+IEV2ZXIgc2luY2Ug Y29tbWl0IDI1NGQxYTNmMDJlYiAoInhlbi9wdi1vbi1odm0ga2V4ZWM6IHNodXRkb3duIHdhdGNo ZXMNCiAgICA+IGZyb20gb2xkIGtlcm5lbCIpIHVzaW5nIHRoZSBJTlR4IGludGVycnVwdCBmcm9t IFhlbiBQQ0kgcGxhdGZvcm0gZGV2aWNlIGZvcg0KICAgID4gZXZlbnQgY2hhbm5lbCBub3RpZmlj YXRpb24gd291bGQganVzdCBsb2NrdXAgdGhlIGd1ZXN0IGR1cmluZyBib290dXAuDQogICAgPiBw b3N0Y29yZV9pbml0Y2FsbCBub3cgY2FsbHMgeHNfcmVzZXRfd2F0Y2hlcyB3aGljaCB3aWxsIGV2 ZW50dWFsbHkgdHJ5IHRvIHJlYWQNCiAgICA+IGEgdmFsdWUgZnJvbSBYZW5TdG9yZSBhbmQgd2ls bCBnZXQgc3R1Y2sgb24gcmVhZF9yZXBseSBhdCBYZW5CdXMgZm9yZXZlciBzaW5jZQ0KICAgID4g dGhlIHBsYXRmb3JtIGRyaXZlciBpcyBub3QgcHJvYmVkIHlldCBhbmQgaXRzIElOVHggaW50ZXJy dXB0IGhhbmRsZXIgaXMgbm90DQogICAgPiByZWdpc3RlcmVkIHlldC4gVGhhdCBtZWFucyB0aGF0 IHRoZSBndWVzdCBjYW4gbm90IGJlIG5vdGlmaWVkIGF0IHRoaXMgbW9tZW50IG9mDQogICAgPiBh bnkgcGVuZGluZyBldmVudCBjaGFubmVscyBhbmQgbm9uZSBvZiB0aGUgcGVyLWV2ZW50IGhhbmRs ZXJzIHdpbGwgZXZlciBiZQ0KICAgID4gaW52b2tlZCAoaW5jbHVkaW5nIHRoZSBYZW5TdG9yZSBv bmUpIGFuZCB0aGUgcmVwbHkgd2lsbCBuZXZlciBiZSBwaWNrZWQgdXAgYnkNCiAgICA+IHRoZSBr ZXJuZWwuDQogICAgDQogICAgQXBwbGllZCB0byBmb3ItbGludXMtNC45LCB0aGFua3MuDQogICAg DQogICAgRGF2aWQNCiAgICANCiAgICANCiAgICANCg0KQW1hem9uIERldmVsb3BtZW50IENlbnRl ciBHZXJtYW55IEdtYkgKQmVybGluIC0gRHJlc2RlbiAtIEFhY2hlbgptYWluIG9mZmljZTogS3Jh dXNlbnN0ci4gMzgsIDEwMTE3IEJlcmxpbgpHZXNjaGFlZnRzZnVlaHJlcjogRHIuIFJhbGYgSGVy YnJpY2gsIENocmlzdGlhbiBTY2hsYWVnZXIKVXN0LUlEOiBERTI4OTIzNzg3OQpFaW5nZXRyYWdl biBhbSBBbXRzZ2VyaWNodCBDaGFybG90dGVuYnVyZyBIUkIgMTQ5MTczIEIK
next prev parent reply other threads:[~2017-04-10 12:28 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-08-26 21:55 [PATCH] xen: Remove event channel notification through Xen PCI platform device KarimAllah Ahmed 2016-08-26 21:55 ` KarimAllah Ahmed 2016-08-29 17:29 ` Boris Ostrovsky 2016-08-29 17:29 ` Boris Ostrovsky 2016-09-30 14:46 ` David Vrabel 2016-09-30 14:46 ` [Xen-devel] " David Vrabel 2017-04-10 12:28 ` Raslan, KarimAllah 2017-04-10 12:28 ` Raslan, KarimAllah [this message] 2017-04-10 12:28 ` [Xen-devel] " Raslan, KarimAllah
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