Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753193AbbFHPui (ORCPT ); Mon, 8 Jun 2015 11:50:38 -0400 Received: from casper.infradead.org ([85.118.1.10]:43857 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753106AbbFHPu2 (ORCPT ); Mon, 8 Jun 2015 11:50:28 -0400 Message-ID: <1433778624.2952.82.camel@infradead.org> Subject: Re: [PATCH v11 0/10] iommu/vt-d: Fix intel vt-d faults in kdump kernel From: David Woodhouse To: Joerg Roedel Cc: bhe@redhat.com, tom.vaden@hp.com, rwright@hp.com, linux-pci@vger.kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, lisa.mitchell@hp.com, iommu@lists.linux-foundation.org, "Li, Zhen-Hua" , doug.hatch@hp.com, ishii.hironobu@jp.fujitsu.com, bhelgaas@google.com, billsumnerlinux@gmail.com, li.zhang6@hp.com, dyoung@redhat.com, vgoyal@redhat.com Date: Mon, 08 Jun 2015 16:50:24 +0100 In-Reply-To: <20150608152957.GW20384@8bytes.org> References: <1431337974-545-1-git-send-email-zhen-hual@hp.com> <1433773583.2952.52.camel@infradead.org> <20150608152957.GW20384@8bytes.org> Content-Type: multipart/signed; micalg="sha-1"; protocol="application/x-pkcs7-signature"; boundary="=-T8BtOgq74pECZEh1hTfz" X-Mailer: Evolution 3.16.2.1 (3.16.2.1-2.fc22) Mime-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 10475 Lines: 167 --=-T8BtOgq74pECZEh1hTfz Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, 2015-06-08 at 17:29 +0200, Joerg Roedel wrote: > On Mon, Jun 08, 2015 at 03:26:23PM +0100, David Woodhouse wrote: > > There are some interesting corner cases to handle here. > >=20 > > Firstly, you don't seem to handle the case of extended root/context > > tables (where ecap_ecs is set). You need to preserve the DMA_RTADDR_RT > > bit in the Root Table Address register, surely? > >=20 > > I think we also need to cope with inheriting page tables from a kernel > > that *doesn't* use extended page tables, even on hardware that supports > > it. Which means the use of extended page tables in the new kernel would > > need to be contingent on something *other* than the pure hardware > > capabilities. >=20 > Hmm, I also limited this functionality to kdump kernels. Do we still > need to preserve these extended data structures even when there is no > upstream support for them yet? We *do* have upstream support. The 4.1 kernel will use the extended root/context tables and will set the DMA_RTADDR_RTT bit in the Root Table Address register, even though it doesn't yet actually *use* any of the shiny new bits in the extended context tables. So the code which copies the context tables needs to take that into account. > That is still a problem, but not specific to this patch-set. RMRRs will > not be restored, because domains allocated out of the DMA-API path will > not get any RMRR mappings. This is also a problem with device hotplug > (unplug a device with RMRRs and replug it in and the RMRR mappings will > be gone). >=20 > I agree that this needs to be fixed. Yeah. We need the same thing with hardware passthrough =E2=80=94 currently = I think we refuse to put RMRR-afflicted devices into the passthrough domain purely because we lack the capability to install the RMRR regions if/when we later take it *out* of the hardware passthrough domain. Although I can't quite remember the logic there; surely if it's RMRR-afflicted and we have iommu=3Dpt, it'll *never* be taken out of the 1:1 domain? A device driver might come along and tell us it really is 64-bit capable and thus we might put it *in* to the passthrough domain where previously we'd kept it out... but taking it *out*... ? --=20 dwmw2 --=-T8BtOgq74pECZEh1hTfz Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIISjjCCBicw ggUPoAMCAQICAw3vNzANBgkqhkiG9w0BAQUFADCBjDELMAkGA1UEBhMCSUwxFjAUBgNVBAoTDVN0 YXJ0Q29tIEx0ZC4xKzApBgNVBAsTIlNlY3VyZSBEaWdpdGFsIENlcnRpZmljYXRlIFNpZ25pbmcx ODA2BgNVBAMTL1N0YXJ0Q29tIENsYXNzIDEgUHJpbWFyeSBJbnRlcm1lZGlhdGUgQ2xpZW50IENB MB4XDTE1MDUwNTA5NDM0MVoXDTE2MDUwNTA5NTMzNlowQjEcMBoGA1UEAwwTZHdtdzJAaW5mcmFk ZWFkLm9yZzEiMCAGCSqGSIb3DQEJARYTZHdtdzJAaW5mcmFkZWFkLm9yZzCCASIwDQYJKoZIhvcN AQEBBQADggEPADCCAQoCggEBAMkbm9kPbx1j/X4RVyf/pPKSYwelcco69TvnQQbKM8m8xkWjXJI1 jpJ1jMaGUZGFToINMSZi7lZawUozudWbXSKy1SikENSTJHffsdRAIlsp+hR8vWvjsKUry6sEdqPG 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