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If we view that mapping as an > > > attribute of the iommu domain, it's reasonable to have the userspace- > > bound > > > pgtable through /dev/ioasid to nest on it. > > > > A user controlled page table should absolutely not be an attribute of > > a hidden kernel object, nor should two parts of the kernel silently > > connect to each other via a hidden internal objects like this. > > > > Security is important - the kind of connection must use some explicit > > FD authorization to access shared objects, not be made implicit! > > > > IMHO this direction is a dead end for this reason. > > > > Could you elaborate what exact security problem is brought with this > approach? Isn't ALLOW_PASID the authorization interface for the > connection? If the kernel objects don't come out of FDs then no. > Is it really the only practice in Linux that any new feature has to be > blocked as long as a refactoring work is identified? The practice is to define uAPIs that make sense and have a good chance to be supported over a long time period, as the software evolves, not to hacky hacky a gaint uAPI mess just to get some feature out the door. This proposal as it was oringial shown is exactly the kind of hacky hacky uapi nobody wants to see. Tunneling an IOMMU uapi through a whole bunch of other FDs is completely nutz. Intel should basically be investing most of its time building a robust and well designed uAPI here, and don't complain that the community is not doing Intel's job for free. > Don't people accept any balance between enabling new features and > completing refactoring work through a staging approach, as long as > we don't introduce an uAPI specifically for the staging purpose? ☹ Since this is all uapi I don't see it as applicable here. 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charset="utf-8" Content-Transfer-Encoding: base64 Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" T24gV2VkLCBBcHIgMDcsIDIwMjEgYXQgMTE6NTA6MDJQTSArMDAwMCwgVGlhbiwgS2V2aW4gd3Jv dGU6Cj4gPiBGcm9tOiBKYXNvbiBHdW50aG9ycGUgPGpnZ0BudmlkaWEuY29tPgo+ID4gU2VudDog V2VkbmVzZGF5LCBBcHJpbCA3LCAyMDIxIDg6MjEgUE0KPiA+IAo+ID4gT24gV2VkLCBBcHIgMDcs IDIwMjEgYXQgMDI6MDg6MzNBTSArMDAwMCwgVGlhbiwgS2V2aW4gd3JvdGU6Cj4gPiAKPiA+ID4g PiBCZWNhdXNlIGlmIHlvdSBkb24ndCB0aGVuIHdlIGVudGVyIGluc2FuZSB3b3JsZCB3aGVyZSBh IFBBU0lEIGlzIGJlaW5nCj4gPiA+ID4gY3JlYXRlZCB1bmRlciAvZGV2L2lvYXNpZCBidXQgaXRz IHRyYW5zbGF0aW9uIHBhdGggZmxvd3MgdGhyb3VnaCBzZXR1cAo+ID4gPiA+IGRvbmUgYnkgVkZJ TyBhbmQgdGhlIHdob2xlIHVzZXIgQVBJIGJlY29tZXMgYW4gaW5jb21wcmVoZW5zaWJsZQo+ID4g bWVzcy4KPiA+ID4gPgo+ID4gPiA+IEhvdyB3aWxsIHlvdSBldmVuIGFzc29jaWF0ZSB0aGUgUEFT SUQgd2l0aCB0aGUgb3RoZXIgdHJhbnNsYXRpb24/Pwo+ID4gPgo+ID4gPiBQQVNJRCBpcyBhdHRh Y2hlZCB0byBhIHNwZWNpZmljIGlvbW11IGRvbWFpbiAoY3JlYXRlZCBieSBWRklPL1ZEUEEpLAo+ ID4gd2hpY2gKPiA+ID4gaGFzIEdQQS0+SFBBIG1hcHBpbmdzIGFscmVhZHkgY29uZmlndXJlZC4g SWYgd2UgdmlldyB0aGF0IG1hcHBpbmcgYXMgYW4KPiA+ID4gYXR0cmlidXRlIG9mIHRoZSBpb21t dSBkb21haW4sIGl0J3MgcmVhc29uYWJsZSB0byBoYXZlIHRoZSB1c2Vyc3BhY2UtCj4gPiBib3Vu ZAo+ID4gPiBwZ3RhYmxlIHRocm91Z2ggL2Rldi9pb2FzaWQgdG8gbmVzdCBvbiBpdC4KPiA+IAo+ ID4gQSB1c2VyIGNvbnRyb2xsZWQgcGFnZSB0YWJsZSBzaG91bGQgYWJzb2x1dGVseSBub3QgYmUg YW4gYXR0cmlidXRlIG9mCj4gPiBhIGhpZGRlbiBrZXJuZWwgb2JqZWN0LCBub3Igc2hvdWxkIHR3 byBwYXJ0cyBvZiB0aGUga2VybmVsIHNpbGVudGx5Cj4gPiBjb25uZWN0IHRvIGVhY2ggb3RoZXIg dmlhIGEgaGlkZGVuIGludGVybmFsIG9iamVjdHMgbGlrZSB0aGlzLgo+ID4gCj4gPiBTZWN1cml0 eSBpcyBpbXBvcnRhbnQgLSB0aGUga2luZCBvZiBjb25uZWN0aW9uIG11c3QgdXNlIHNvbWUgZXhw bGljaXQKPiA+IEZEIGF1dGhvcml6YXRpb24gdG8gYWNjZXNzIHNoYXJlZCBvYmplY3RzLCBub3Qg YmUgbWFkZSBpbXBsaWNpdCEKPiA+IAo+ID4gSU1ITyB0aGlzIGRpcmVjdGlvbiBpcyBhIGRlYWQg ZW5kIGZvciB0aGlzIHJlYXNvbi4KPiA+IAo+IAo+IENvdWxkIHlvdSBlbGFib3JhdGUgd2hhdCBl eGFjdCBzZWN1cml0eSBwcm9ibGVtIGlzIGJyb3VnaHQgd2l0aCB0aGlzIAo+IGFwcHJvYWNoPyBJ c24ndCBBTExPV19QQVNJRCB0aGUgYXV0aG9yaXphdGlvbiBpbnRlcmZhY2UgZm9yIHRoZQo+IGNv bm5lY3Rpb24/CgpJZiB0aGUga2VybmVsIG9iamVjdHMgZG9uJ3QgY29tZSBvdXQgb2YgRkRzIHRo ZW4gbm8uCgo+IElzIGl0IHJlYWxseSB0aGUgb25seSBwcmFjdGljZSBpbiBMaW51eCB0aGF0IGFu eSBuZXcgZmVhdHVyZSBoYXMgdG8gYmUKPiBibG9ja2VkIGFzIGxvbmcgYXMgYSByZWZhY3Rvcmlu ZyB3b3JrIGlzIGlkZW50aWZpZWQ/IAoKVGhlIHByYWN0aWNlIGlzIHRvIGRlZmluZSB1QVBJcyB0 aGF0IG1ha2Ugc2Vuc2UgYW5kIGhhdmUgYSBnb29kIGNoYW5jZQp0byBiZSBzdXBwb3J0ZWQgb3Zl ciBhIGxvbmcgdGltZSBwZXJpb2QsIGFzIHRoZSBzb2Z0d2FyZSBldm9sdmVzLCBub3QKdG8gaGFj a3kgaGFja3kgYSBnYWludCB1QVBJIG1lc3MganVzdCB0byBnZXQgc29tZSBmZWF0dXJlIG91dCB0 aGUKZG9vci4gCgpUaGlzIHByb3Bvc2FsIGFzIGl0IHdhcyBvcmluZ2lhbCBzaG93biBpcyBleGFj dGx5IHRoZSBraW5kIG9mIGhhY2t5CmhhY2t5IHVhcGkgbm9ib2R5IHdhbnRzIHRvIHNlZS4gVHVu bmVsaW5nIGFuIElPTU1VIHVhcGkgdGhyb3VnaCBhCndob2xlIGJ1bmNoIG9mIG90aGVyIEZEcyBp cyBjb21wbGV0ZWx5IG51dHouCgpJbnRlbCBzaG91bGQgYmFzaWNhbGx5IGJlIGludmVzdGluZyBt b3N0IG9mIGl0cyB0aW1lIGJ1aWxkaW5nIGEgcm9idXN0CmFuZCB3ZWxsIGRlc2lnbmVkIHVBUEkg aGVyZSwgYW5kIGRvbid0IGNvbXBsYWluIHRoYXQgdGhlIGNvbW11bml0eSBpcwpub3QgZG9pbmcg SW50ZWwncyBqb2IgZm9yIGZyZWUuCgo+IERvbid0IHBlb3BsZSBhY2NlcHQgYW55IGJhbGFuY2Ug YmV0d2VlbiBlbmFibGluZyBuZXcgZmVhdHVyZXMgYW5kCj4gY29tcGxldGluZyByZWZhY3Rvcmlu ZyB3b3JrIHRocm91Z2ggYSBzdGFnaW5nIGFwcHJvYWNoLCBhcyBsb25nIGFzCj4gd2UgZG9uJ3Qg aW50cm9kdWNlIGFuIHVBUEkgc3BlY2lmaWNhbGx5IGZvciB0aGUgc3RhZ2luZyBwdXJwb3NlPyDi mLkKClNpbmNlIHRoaXMgaXMgYWxsIHVhcGkgSSBkb24ndCBzZWUgaXQgYXMgYXBwbGljYWJsZSBo ZXJlLgoKSmFzb24KX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X18KaW9tbXUgbWFpbGluZyBsaXN0CmlvbW11QGxpc3RzLmxpbnV4LWZvdW5kYXRpb24ub3JnCmh0 dHBzOi8vbGlzdHMubGludXhmb3VuZGF0aW9uLm9yZy9tYWlsbWFuL2xpc3RpbmZvL2lvbW11 From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: [PATCH V4 05/18] iommu/ioasid: Redefine IOASID set and allocation APIs Date: Thu, 8 Apr 2021 08:41:13 -0300 Message-ID: <20210408114113.GN7405@nvidia.com> References: <20210329163147.GG2356281@nvidia.com> <20210330132830.GO2356281@nvidia.com> <20210405234230.GF7405@nvidia.com> <20210406123451.GN7405@nvidia.com> <20210407122042.GF7405@nvidia.com> Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=48OHsp5mI3yQn9DHcjJ1PrziL5UqaHpzIRwLXkKu7z0=; b=eHaPZOGQChk9LAHLgFwQD7YeZuLpMvNdeyclyCf7PB2H4FY7mAjGNyAp7qO0UO6KK+5AgDh1WrBY/2ZIimgmxDh1B38HLLStt1FjSV6mn4qmMB1QDKZjtlI1xwbWO5c2PeW2y2XMrUBVtdZ1oCXMNkzwZ3LDY6FybWDl9/brPgvQ2yvnEtCyocJQs1WQXF5soAHdnch8E5O+gJiwayiVFaOKsOjgbexxddaVlBxQT7yEnQTq4PjHmTYHSlMcxw0GOCCCGD76njQxYXp+8sjhAIWzuu4Z5htTQqNdjA0sbhqAzykjShPpDIztYCzULHzZVAHwlLkx+4wvNhfIxuwoag== Content-Disposition: inline In-Reply-To: List-ID: Content-Type: text/plain; charset="windows-1252" To: "Tian, Kevin" Cc: Jean-Philippe Brucker , Alex Williamson , "Raj, Ashok" , Jonathan Corbet , Jean-Philippe Brucker , LKML , "Jiang, Dave" , "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" , Li Zefan , Johannes Weiner , Tejun Heo , "cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "Wu, Hao" , David Woodhouse , Jason Wang On Wed, Apr 07, 2021 at 11:50:02PM +0000, Tian, Kevin wrote: > > From: Jason Gunthorpe > > Sent: Wednesday, April 7, 2021 8:21 PM > >=20 > > On Wed, Apr 07, 2021 at 02:08:33AM +0000, Tian, Kevin wrote: > >=20 > > > > Because if you don't then we enter insane world where a PASID is be= ing > > > > created under /dev/ioasid but its translation path flows through se= tup > > > > done by VFIO and the whole user API becomes an incomprehensible > > mess. > > > > > > > > How will you even associate the PASID with the other translation?? > > > > > > PASID is attached to a specific iommu domain (created by VFIO/VDPA), > > which > > > has GPA->HPA mappings already configured. If we view that mapping as = an > > > attribute of the iommu domain, it's reasonable to have the userspace- > > bound > > > pgtable through /dev/ioasid to nest on it. > >=20 > > A user controlled page table should absolutely not be an attribute of > > a hidden kernel object, nor should two parts of the kernel silently > > connect to each other via a hidden internal objects like this. > >=20 > > Security is important - the kind of connection must use some explicit > > FD authorization to access shared objects, not be made implicit! > >=20 > > IMHO this direction is a dead end for this reason. > >=20 >=20 > Could you elaborate what exact security problem is brought with this=20 > approach? Isn't ALLOW_PASID the authorization interface for the > connection? If the kernel objects don't come out of FDs then no. > Is it really the only practice in Linux that any new feature has to be > blocked as long as a refactoring work is identified?=20 The practice is to define uAPIs that make sense and have a good chance to be supported over a long time period, as the software evolves, not to hacky hacky a gaint uAPI mess just to get some feature out the door.=20 This proposal as it was oringial shown is exactly the kind of hacky hacky uapi nobody wants to see. Tunneling an IOMMU uapi through a whole bunch of other FDs is completely nutz. Intel should basically be investing most of its time building a robust and well designed uAPI here, and don't complain that the community is not doing Intel's job for free. > Don't people accept any balance between enabling new features and > completing refactoring work through a staging approach, as long as > we don't introduce an uAPI specifically for the staging purpose? =E2=98=B9 Since this is all uapi I don't see it as applicable here. Jason