From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755916AbdEEULY (ORCPT ); Fri, 5 May 2017 16:11:24 -0400 Received: from twosheds.infradead.org ([90.155.92.209]:44748 "EHLO twosheds.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751529AbdEEULX (ORCPT ); Fri, 5 May 2017 16:11:23 -0400 Message-ID: <1494010606.6350.27.camel@infradead.org> Subject: Re: [PATCH] iommu: intel: Flush the IOTLB to get rid of the initial kdump mappings From: David Woodhouse To: KarimAllah Ahmed , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org Cc: Joerg Roedel , Anthony Liguori In-Reply-To: <1494009599-20962-1-git-send-email-karahmed@amazon.de> References: <1494009599-20962-1-git-send-email-karahmed@amazon.de> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/x-pkcs7-signature"; boundary="=-siLdc7PfluMgMw7bmui5" Date: Fri, 05 May 2017 20:56:46 +0200 Mime-Version: 1.0 X-Mailer: Evolution 3.18.5.2-0ubuntu3.1 X-SRS-Rewrite: SMTP reverse-path rewritten from by twosheds.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 --=-siLdc7PfluMgMw7bmui5 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, 2017-05-05 at 11:39 -0700, KarimAllah Ahmed wrote: > Ever since commit 091d42e43d ("iommu/vt-d: Copy translation tables from > old kernel") the kdump kernel copies the IOMMU context tables from the > previous kernel. Each device mappings will be destroyed once the driver > for the respective device takes over. >=20 > This unfortunately breaks the workflow of mapping and unmapping a new > context to the IOMMU. The mapping function assumes that either: >=20 > 1) Unmapping did the proper IOMMU flushing and it only ever flush if the > =C2=A0=C2=A0=C2=A0IOMMU unit supports caching invalid entries. > 2) The system just booted and the initialization code took care of > =C2=A0=C2=A0=C2=A0flushing all IOMMU caches. >=20 > This assumption is not true for the kdump kernel since the context > tables have been copied from the previous kernel and translations could > have been cached ever since. So make sure to flush the IOTLB as well > when we destroy these old copied mappings. >=20 > Cc: Joerg Roedel > Cc: David Woodhouse > Cc: David Woodhouse > Cc: Anthony Liguori > Signed-off-by: KarimAllah Ahmed Acked-by: David Woodhouse Cc: stable@vger.kernel.org=C2=A0 v4.2+ I'm still moderately unhappy about the whole "preserve existing mappings during kdump" thing, and wanted to have a PCI quirk for the known-broken-can't-be-reset-after-fault devices, and trigger this behaviour only then. Although I have a vague recollection of there being a slightly saner justification for it... perhaps this should be documented, if there is one? --=-siLdc7PfluMgMw7bmui5 Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCDzUw ggSvMIIDl6ADAgECAhEA4CPLFRKDU4mtYW56VGdrITANBgkqhkiG9w0BAQsFADBvMQswCQYDVQQG EwJTRTEUMBIGA1UEChMLQWRkVHJ1c3QgQUIxJjAkBgNVBAsTHUFkZFRydXN0IEV4dGVybmFsIFRU UCBOZXR3b3JrMSIwIAYDVQQDExlBZGRUcnVzdCBFeHRlcm5hbCBDQSBSb290MB4XDTE0MTIyMjAw MDAwMFoXDTIwMDUzMDEwNDgzOFowgZsxCzAJBgNVBAYTAkdCMRswGQYDVQQIExJHcmVhdGVyIE1h bmNoZXN0ZXIxEDAOBgNVBAcTB1NhbGZvcmQxGjAYBgNVBAoTEUNPTU9ETyBDQSBMaW1pdGVkMUEw PwYDVQQDEzhDT01PRE8gU0hBLTI1NiBDbGllbnQgQXV0aGVudGljYXRpb24gYW5kIFNlY3VyZSBF bWFpbCBDQTCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAImxDdp6UxlOcFIdvFamBia3 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