From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Woodhouse Subject: Re: [PATCH 6/9] drm/i915: driver based PASID handling Date: Wed, 07 Oct 2015 18:17:18 +0100 Message-ID: <1444238238.4674.329.camel@infradead.org> References: <1441385943-11508-1-git-send-email-jbarnes@virtuousgeek.org> <1441385943-11508-7-git-send-email-jbarnes@virtuousgeek.org> <1444222816.4674.322.camel@infradead.org> <5615375A.6070705@virtuousgeek.org> <20151007161424.GV3383@phenom.ffwll.local> <56154821.3090204@virtuousgeek.org> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============1819389738==" Return-path: Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) by gabe.freedesktop.org (Postfix) with ESMTPS id 92A096E36B for ; Wed, 7 Oct 2015 10:17:26 -0700 (PDT) In-Reply-To: <56154821.3090204@virtuousgeek.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" To: Jesse Barnes , Daniel Vetter Cc: intel-gfx@lists.freedesktop.org List-Id: intel-gfx@lists.freedesktop.org --===============1819389738== Content-Type: multipart/signed; micalg="sha-1"; protocol="application/x-pkcs7-signature"; boundary="=-F1/qpS+jLaFXs2P1elH4" --=-F1/qpS+jLaFXs2P1elH4 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, 2015-10-07 at 09:28 -0700, Jesse Barnes wrote: > On 10/07/2015 09:14 AM, Daniel Vetter wrote: > > On Wed, Oct 07, 2015 at 08:16:42AM -0700, Jesse Barnes wrote: > > > On 10/07/2015 06:00 AM, David Woodhouse wrote: > > > > On Fri, 2015-09-04 at 09:59 -0700, Jesse Barnes wrote: > > > > > + > > > > > + ret =3D handle_mm_fault(mm, vma, address, > > > > > + desc.wr_req ? FAULT_FLAG_WRITE : 0)= ; > > > > > + if (ret & VM_FAULT_ERROR) { > > > > > + gpu_mm_segv(tsk, address, SEGV_ACCERR); /* ? */ > > > > > + goto out_unlock; > > > > > + } > > > > > + > > > >=20 > > > > Hm, do you need to force the SEGV there, in what ought to be generi= c > > > > IOMMU code? > > > >=20 > > > > Can you instead just let the fault handler return an appropriate > > > > failure code to the IOMMU request queue and then deal with the > > > > resulting error on the i915 device side? > > >=20 > > > I'm not sure if we get enough info on the i915 side to handle it > > > reasonably, we'll have to test that out. > >=20 > > We do know precisely which context blew up, but without the TDR work we > > can't yet just kill the offender selective without affecting the other > > active gpu contexts. >=20 > How? The notification from the IOMMU queue is asynchronous... The page request, and the response, include 'private data' which an endpoint can use to carry that kind of information. In $7.5.1.1 of the VT-d specification it tells us: "Private Data: The Private Data field can be used by=20 Root-Complex integrated endpoints to uniquely identify device-specific private information associated with an=20 individual page request. "For Intel =C2=AE Processor Graphics device, the Private Data field=20 specifies the identity of the GPU advanced-context (see=20 Section 3.10) sending the page request." > > But besides that I really don't see a reason why we need to kill the > > process if the gpu faults. After all if a thread sigfaults then signal > > goes to that thread and not some random one (or the one thread that for= ked > > the thread that blew up). And we do have interfaces to tell userspace t= hat > > something bad happened with the gpu work it submitted. I certainly don't want the core IOMMU code killing things. I really want to just complete the page request with an appropriate failure code, and let the endpoint device deal with it from there. --=20 David Woodhouse Open Source Technology Centre David.Woodhouse@intel.com Intel Corporation --=-F1/qpS+jLaFXs2P1elH4 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 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