From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f176.google.com (mail-ig0-f176.google.com [209.85.213.176]) by kanga.kvack.org (Postfix) with ESMTP id 262DB6B0253 for ; Tue, 20 Oct 2015 12:17:09 -0400 (EDT) Received: by igbdj2 with SMTP id dj2so18032378igb.1 for ; Tue, 20 Oct 2015 09:17:09 -0700 (PDT) Received: from bombadil.infradead.org (bombadil.infradead.org. [2001:1868:205::9]) by mx.google.com with ESMTPS id b18si3710217ioe.127.2015.10.20.09.17.08 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 20 Oct 2015 09:17:08 -0700 (PDT) Message-ID: <1445357824.4486.65.camel@infradead.org> Subject: Re: [RFC PATCH] iommu/vt-d: Add IOTLB flush support for kernel addresses From: David Woodhouse Date: Tue, 20 Oct 2015 17:17:04 +0100 In-Reply-To: <20151020160328.GV27420@8bytes.org> References: <1445356379.4486.56.camel@infradead.org> <20151020160328.GV27420@8bytes.org> Content-Type: multipart/signed; micalg="sha-1"; protocol="application/x-pkcs7-signature"; boundary="=-YVuYjNhqKD8cuh5/Ik8k" Mime-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Joerg Roedel Cc: "linux-mm@kvack.org" , iommu@lists.linux-foundation.org, Sudeep Dutt --=-YVuYjNhqKD8cuh5/Ik8k Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Tue, 2015-10-20 at 18:03 +0200, Joerg Roedel wrote: > Hi David, >=20 > On Tue, Oct 20, 2015 at 04:52:59PM +0100, David Woodhouse wrote: > > void flush_tlb_kernel_range(unsigned long start, unsigned long end) > > { > > +> > > > intel_iommu_flush_kernel_pasid(start, end); >=20 > A more generic naming would be good, and probably expose it through a > function in the IOMMU-API. Yeah. *All* the SVM functionality needs to be exposed through the DMA API (for native drivers like i915) and the IOMMU API (so VM guests can see an IOMMU and do SVM on assigned devices). Can we assume that only one type of SVM-capable IOMMU will be present in the system at a time? Perhaps we could just register a single function (intel_iommu_flush_kernel_pasid in the VT-d case) to be used as a notifier callback from tlb_flush_kernel_range()? Rather than the overhead of a *list* of notifiers? > > +void intel_iommu_flush_kernel_pasid(unsigned long start, unsigned long= end) > > +{ > > +> > > > struct dmar_drhd_unit *drhd; > > +> > > > struct intel_iommu *iommu; > > +> > > > unsigned long pages; >=20 > And I think, as a performance optimiztion, we should bail out early here > if the pasid has no users. If the PASID has no users, it won't exist (iommu->kernel_svm will be NULL). We still have to walk each IOMMU to see if it has one. But... that's because the PASID-space is currently per-IOMMU. The plan is to have a *single* PASID-space system-wide, And then I still want to retain the property that there can be only *one* kernel PASID. I have forbidden the use of a given PASID to access *both* kernel and user addresses. I'm hoping we can get away with putting that restriction into the generic SVM APIs. So yeah, perhaps we can set the notifier pointer to NULL when there's no kernel PASID assigned, and only set it to point to ${MY_IOMMU}_flush_kernel_pasid() if/when there *is* one? That way, tlb_flush_kernel_range() doesn't even need to make the call when there's no work to do... --=20 dwmw2 --=-YVuYjNhqKD8cuh5/Ik8k 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 doa5RY7+N4WRusWZDYW/RRWE6i9EL9qV86CVPYqw22UBOUw4/j/HVGCV6TSB8yE5iEwhk/hUuzRr 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