From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joonas Lahtinen Subject: Re: [PATCH v2] drm/i915: Drop support for I915_EXEC_CONSTANTS_* execbuf parameters. Date: Wed, 15 Feb 2017 09:38:43 +0200 Message-ID: <1487144323.8490.3.camel@linux.intel.com> References: <20170215041751.11441-1-kenneth@whitecape.org> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by gabe.freedesktop.org (Postfix) with ESMTPS id CFD336E1EF for ; Wed, 15 Feb 2017 07:38:46 +0000 (UTC) In-Reply-To: <20170215041751.11441-1-kenneth@whitecape.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" To: Kenneth Graunke , intel-gfx@lists.freedesktop.org Cc: Dave Gordon , stable@vger.kernel.org List-Id: intel-gfx@lists.freedesktop.org T24gdGksIDIwMTctMDItMTQgYXQgMjA6MTcgLTA4MDAsIEtlbm5ldGggR3JhdW5rZSB3cm90ZToK PiBUaGlzIHBhdGNoIG1ha2VzIHRoZSBJOTE1X1BBUkFNX0hBU19FWEVDX0NPTlNUQU5UUyBnZXRw YXJhbSByZXR1cm4gMAo+IChpbmRpY2F0aW5nIHRoZSBvcHRpb25hbCBmZWF0dXJlIGlzIG5vdCBz dXBwb3J0ZWQpLCBhbmQgbWFrZXMgZXhlY2J1Zgo+IGFsd2F5cyByZXR1cm4gLUVJTlZBTCBpZiB0 aGUgZmxhZ3MgYXJlIHVzZWQuCj4gCj4gQXBwYXJlbnRseSwgbm8gdXNlcnNwYWNlIGV2ZXIgc2hp cHBlZCB3aGljaCB1c2VkIHRoaXMgb3B0aW9uYWwgZmVhdHVyZToKPiBJIGNoZWNrZWQgdGhlIGdp dCBoaXN0b3J5IG9mIE1lc2EsIHhmODYtdmlkZW8taW50ZWwsIGxpYnZhLCBhbmQgQmVpZ25ldCwK PiBhbmQgdGhlcmUgd2VyZSB6ZXJvIGNvbW1pdHMgc2hvd2luZyBhIHVzZSBvZiB0aGVzZSBmbGFn cy7CoMKgS2VybmVsIGNvbW1pdAo+IDcyYmZhMTljOGRlYjQgYXBwYXJlbnRseSBpbnRyb2R1Y2Vk IHRoZSBmZWF0dXJlIHByZW1hdHVyZWx5Lgo+IAo+ICdyZWxhdGl2ZV9jb25zdGFudHNfbW9kZScg aGFzIGFsd2F5cyBiZWVuIHRyYWNrZWQgcGVyLWRldmljZSwgYnV0IHRoaXMKPiBoYXMgYWN0dWFs bHkgYmVlbiB3cm9uZyBldmVyIHNpbmNlIGhhcmR3YXJlIGNvbnRleHRzIHdlcmUgaW50cm9kdWNl ZCwgYXMKPiB0aGUgSU5TVFBNIHJlZ2lzdGVyIGlzIHNhdmVkIChhbmQgYXV0b21hdGljYWxseSBy ZXN0b3JlZCkgYXMgcGFydCBvZiB0aGUKPiByZW5kZXIgcmluZyBjb250ZXh0LiBUaGUgc29mdHdh cmUgcGVyLWRldmljZSB2YWx1ZSBjb3VsZCB0aGVyZWZvcmUgZ2V0Cj4gb3V0IG9mIHN5bmMgd2l0 aCB0aGUgaGFyZHdhcmUgcGVyLWNvbnRleHQgdmFsdWUuwqDCoFRoaXMgbWVhbnQgdGhhdCB1c2lu Zwo+IHRoZW0gaXMgYWN0dWFsbHkgdW5zYWZlOiBhIGNsaWVudCB3aGljaCB0cmllZCB0byB1c2Ug dGhlbSBjb3VsZCBkYW1hZ2UKPiB0aGUgc3RhdGUgb2Ygb3RoZXIgY2xpZW50cywgY2F1c2luZyB0 aGUgR1BVIHRvIGludGVycHJldCB0aGVpciBCTwo+IG9mZnNldHMgYXMgYWJzb2x1dGUgcG9pbnRl cnMsIGxlYWRpbmcgdG8gYm9ndXMgbWVtb3J5IHJlYWRzLgo+IAo+IFRoZXNlIGZsYWdzIHdlcmUg YWxzbyBuZXZlciBwb3J0ZWQgdG8gZXhlY2xpc3QgbW9kZSwgbWFraW5nIHRoZW0gbm8tb3BzCj4g b24gR2VuOSsgKHdoaWNoIHJlcXVpcmVzIGV4ZWNsaXN0cyksIGFuZCBHZW44IGluIHRoZSBkZWZh dWx0IG1vZGUuCj4gCj4gT24gR2VuOCssIHVzZXJzcGFjZSBjYW4gd3JpdGUgdGhlc2UgcmVnaXN0 ZXJzIGRpcmVjdGx5LCBhY2hpZXZpbmcgdGhlCj4gc2FtZSBlZmZlY3QuwqDCoE9uIEdlbjYtNy41 LCBpdCBsaWtlbHkgbWFrZXMgc2Vuc2UgdG8gZXh0ZW5kIHRoZSBjb21tYW5kCj4gcGFyc2VyIHRv IHN1cHBvcnQgdGhlbS7CoMKgSSBkb24ndCB0aGluayBhbnlvbmUgd2FudHMgdGhpcyBvbiBHZW40 LTUuCj4gCj4gQmFzZWQgb24gYSBwYXRjaCBieSBEYXZlIEdvcmRvbi4KPiAKPiBDYzogRGF2ZSBH b3Jkb24gPGRhdmlkLnMuZ29yZG9uQGludGVsLmNvbT4KPiBDYzogQ2hyaXMgV2lsc29uIDxjaHJp c0BjaHJpcy13aWxzb24uY28udWs+Cj4gQ2M6IHN0YWJsZUB2Z2VyLmtlcm5lbC5vcmcKPiBCdWd6 aWxsYTogaHR0cHM6Ly9idWdzLmZyZWVkZXNrdG9wLm9yZy9zaG93X2J1Zy5jZ2k/aWQ9OTI0NDgK PiBTaWduZWQtb2ZmLWJ5OiBLZW5uZXRoIEdyYXVua2UgPGtlbm5ldGhAd2hpdGVjYXBlLm9yZz4K CkV4cGxhbmF0aW9uIG1ha2VzIHNlbnNlLCBvbmx5IEdvb2dsZSBoaXRzIHNlZW0gdG8gYmUgb24g TWVzYSBkZXRlY3RpbmcKdGhlIGZlYXR1cmUgYW5kIGxhdGVyLCByZW1vdmluZyB0aGUgZGV0ZWN0 aW9uIHdoZW4gdW51c2VkLgoKUmV2aWV3ZWQtYnk6IEpvb25hcyBMYWh0aW5lbiA8am9vbmFzLmxh aHRpbmVuQGxpbnV4LmludGVsLmNvbT4KClJlZ2FyZHMsIEpvb25hcwotLSAKSm9vbmFzIExhaHRp bmVuCk9wZW4gU291cmNlIFRlY2hub2xvZ3kgQ2VudGVyCkludGVsIENvcnBvcmF0aW9uCl9fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fCkludGVsLWdmeCBtYWls aW5nIGxpc3QKSW50ZWwtZ2Z4QGxpc3RzLmZyZWVkZXNrdG9wLm9yZwpodHRwczovL2xpc3RzLmZy ZWVkZXNrdG9wLm9yZy9tYWlsbWFuL2xpc3RpbmZvL2ludGVsLWdmeAo= From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga14.intel.com ([192.55.52.115]:16757 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750711AbdBOHir (ORCPT ); Wed, 15 Feb 2017 02:38:47 -0500 Message-ID: <1487144323.8490.3.camel@linux.intel.com> Subject: Re: [Intel-gfx] [PATCH v2] drm/i915: Drop support for I915_EXEC_CONSTANTS_* execbuf parameters. From: Joonas Lahtinen To: Kenneth Graunke , intel-gfx@lists.freedesktop.org Cc: Dave Gordon , stable@vger.kernel.org Date: Wed, 15 Feb 2017 09:38:43 +0200 In-Reply-To: <20170215041751.11441-1-kenneth@whitecape.org> References: <20170215041751.11441-1-kenneth@whitecape.org> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: On ti, 2017-02-14 at 20:17 -0800, Kenneth Graunke wrote: > This patch makes the I915_PARAM_HAS_EXEC_CONSTANTS getparam return 0 > (indicating the optional feature is not supported), and makes execbuf > always return -EINVAL if the flags are used. > > Apparently, no userspace ever shipped which used this optional feature: > I checked the git history of Mesa, xf86-video-intel, libva, and Beignet, > and there were zero commits showing a use of these flags.  Kernel commit > 72bfa19c8deb4 apparently introduced the feature prematurely. > > 'relative_constants_mode' has always been tracked per-device, but this > has actually been wrong ever since hardware contexts were introduced, as > the INSTPM register is saved (and automatically restored) as part of the > render ring context. The software per-device value could therefore get > out of sync with the hardware per-context value.  This meant that using > them is actually unsafe: a client which tried to use them could damage > the state of other clients, causing the GPU to interpret their BO > offsets as absolute pointers, leading to bogus memory reads. > > These flags were also never ported to execlist mode, making them no-ops > on Gen9+ (which requires execlists), and Gen8 in the default mode. > > On Gen8+, userspace can write these registers directly, achieving the > same effect.  On Gen6-7.5, it likely makes sense to extend the command > parser to support them.  I don't think anyone wants this on Gen4-5. > > Based on a patch by Dave Gordon. > > Cc: Dave Gordon > Cc: Chris Wilson > Cc: stable@vger.kernel.org > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92448 > Signed-off-by: Kenneth Graunke Explanation makes sense, only Google hits seem to be on Mesa detecting the feature and later, removing the detection when unused. Reviewed-by: Joonas Lahtinen Regards, Joonas -- Joonas Lahtinen Open Source Technology Center Intel Corporation