From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A03F6C433F5 for ; Fri, 12 Nov 2021 13:40:44 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6E3BC6103A for ; Fri, 12 Nov 2021 13:40:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 6E3BC6103A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id D5BB06E8EC; Fri, 12 Nov 2021 13:40:42 +0000 (UTC) Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by gabe.freedesktop.org (Postfix) with ESMTPS id 6F8526E8A8; Fri, 12 Nov 2021 13:40:41 +0000 (UTC) X-IronPort-AV: E=McAfee;i="6200,9189,10165"; a="220341042" X-IronPort-AV: E=Sophos;i="5.87,229,1631602800"; d="scan'208";a="220341042" Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Nov 2021 05:40:40 -0800 X-IronPort-AV: E=Sophos;i="5.87,229,1631602800"; d="scan'208";a="670655702" Received: from ggwalsh-mobl.ger.corp.intel.com (HELO [10.213.200.24]) ([10.213.200.24]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Nov 2021 05:40:39 -0800 To: Lu Baolu , Intel-gfx@lists.freedesktop.org References: <20211109121759.170915-1-tvrtko.ursulin@linux.intel.com> <6e8c55a7-45b6-57ab-35f7-d522401efccb@linux.intel.com> <4d1a0ab9-e0d8-2ed9-1fc4-9ffaf2f19bef@linux.intel.com> <7b2e1427-69cf-8f5d-0c15-73c4e602953d@linux.intel.com> <2a1ae709-19f8-7983-b171-98ec2f3f010a@linux.intel.com> <4c5ab72f-aaff-8b92-7471-44dd907cf2f6@linux.intel.com> <24c75ce7-1b14-42e1-a4d4-943e472aed68@linux.intel.com> <2a99dbb9-9ed2-2e3e-b329-21730056d940@linux.intel.com> From: Tvrtko Ursulin Organization: Intel Corporation UK Plc Message-ID: <58616bdc-1150-46dd-5e48-b05f20dc9bc9@linux.intel.com> Date: Fri, 12 Nov 2021 13:40:37 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <2a99dbb9-9ed2-2e3e-b329-21730056d940@linux.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Subject: Re: [Intel-gfx] [PATCH] drm/i915: Use per device iommu check X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: dri-devel@lists.freedesktop.org Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On 12/11/2021 00:53, Lu Baolu wrote: > On 11/11/21 11:06 PM, Tvrtko Ursulin wrote: >> >> On 10/11/2021 12:35, Lu Baolu wrote: >>> On 2021/11/10 20:08, Tvrtko Ursulin wrote: >>>> >>>> On 10/11/2021 12:04, Lu Baolu wrote: >>>>> On 2021/11/10 17:30, Tvrtko Ursulin wrote: >>>>>> >>>>>> On 10/11/2021 07:12, Lu Baolu wrote: >>>>>>> Hi Tvrtko, >>>>>>> >>>>>>> On 2021/11/9 20:17, Tvrtko Ursulin wrote: >>>>>>>> From: Tvrtko Ursulin >>>>>>>> >>>>>>>> On igfx + dgfx setups, it appears that intel_iommu=igfx_off >>>>>>>> option only >>>>>>>> disables the igfx iommu. Stop relying on global >>>>>>>> intel_iommu_gfx_mapped >>>>>>>> and probe presence of iommu domain per device to accurately >>>>>>>> reflect its >>>>>>>> status. >>>>>>>> >>>>>>>> Signed-off-by: Tvrtko Ursulin >>>>>>>> Cc: Lu Baolu >>>>>>>> --- >>>>>>>> Baolu, is my understanding here correct? Maybe I am confused by >>>>>>>> both >>>>>>>> intel_iommu_gfx_mapped and dmar_map_gfx being globals in the >>>>>>>> intel_iommu >>>>>>>> driver. But it certainly appears the setup can assign some iommu >>>>>>>> ops (and >>>>>>>> assign the discrete i915 to iommu group) when those two are set >>>>>>>> to off. >>>>>>> >>>>>>> diff --git a/drivers/gpu/drm/i915/i915_drv.h >>>>>>> b/drivers/gpu/drm/i915/i915_drv.h >>>>>>> index e967cd08f23e..9fb38a54f1fe 100644 >>>>>>> --- a/drivers/gpu/drm/i915/i915_drv.h >>>>>>> +++ b/drivers/gpu/drm/i915/i915_drv.h >>>>>>> @@ -1763,26 +1763,27 @@ static inline bool run_as_guest(void) >>>>>>>   #define HAS_D12_PLANE_MINIMIZATION(dev_priv) >>>>>>> (IS_ROCKETLAKE(dev_priv) || \ >>>>>>>                             IS_ALDERLAKE_S(dev_priv)) >>>>>>> >>>>>>> -static inline bool intel_vtd_active(void) >>>>>>> +static inline bool intel_vtd_active(struct drm_i915_private *i915) >>>>>>>   { >>>>>>> -#ifdef CONFIG_INTEL_IOMMU >>>>>>> -    if (intel_iommu_gfx_mapped) >>>>>>> +    if (iommu_get_domain_for_dev(i915->drm.dev)) >>>>>>>           return true; >>>>>>> -#endif >>>>>>> >>>>>>>       /* Running as a guest, we assume the host is enforcing VT'd */ >>>>>>>       return run_as_guest(); >>>>>>>   } >>>>>>> >>>>>>> Have you verified this change? I am afraid that >>>>>>> iommu_get_domain_for_dev() always gets a valid iommu domain even >>>>>>> intel_iommu_gfx_mapped == 0. >>>>>> >>>>>> Yes it seems to work as is: >>>>>> >>>>>> default: >>>>>> >>>>>> # grep -i iommu /sys/kernel/debug/dri/*/i915_capabilities >>>>>> /sys/kernel/debug/dri/0/i915_capabilities:iommu: enabled >>>>>> /sys/kernel/debug/dri/1/i915_capabilities:iommu: enabled >>>>>> >>>>>> intel_iommu=igfx_off: >>>>>> >>>>>> # grep -i iommu /sys/kernel/debug/dri/*/i915_capabilities >>>>>> /sys/kernel/debug/dri/0/i915_capabilities:iommu: disabled >>>>>> /sys/kernel/debug/dri/1/i915_capabilities:iommu: enabled >>>>>> >>>>>> On my system dri device 0 is integrated graphics and 1 is discrete. >>>>> >>>>> The drm device 0 has a dedicated iommu. When the user request igfx not >>>>> mapped, the VT-d implementation will turn it off to save power. But >>>>> for >>>>> shared iommu, you definitely will get it enabled. >>>> >>>> Sorry I am not following, what exactly do you mean? Is there a >>>> platform with integrated graphics without a dedicated iommu, in >>>> which case intel_iommu=igfx_off results in intel_iommu_gfx_mapped == >>>> 0 and iommu_get_domain_for_dev returning non-NULL? >>> >>> Your code always work for an igfx with a dedicated iommu. This might be >>> always true on today's platforms. But from driver's point of view, we >>> should not make such assumption. >>> >>> For example, if the iommu implementation decides not to turn off the >>> graphic iommu (perhaps due to some hw quirk or for graphic >>> virtualization), your code will be broken. >> >> I tried your suggestion (checking for __IOMMU_DOMAIN_PAGING) and it >> works better, however I have observed one odd behaviour (for me at >> least). >> >> In short - why does the DMAR mode for the discrete device change >> depending on igfx_off parameter? >> >> Consider the laptop has these two graphics cards: >> >> # cat /sys/kernel/debug/dri/0/name >> i915 dev=0000:00:02.0 unique=0000:00:02.0 # integrated >> >> # cat /sys/kernel/debug/dri/1/name >> i915 dev=0000:03:00.0 unique=0000:03:00.0 # discrete >> >> Booting with different options: >> =============================== >> >> default / intel_iommu=on >> ------------------------ >> >> # cat /sys/class/iommu/dmar0/devices/0000:00:02.0/iommu_group/type >> DMA-FQ >> # cat /sys/class/iommu/dmar2/devices/0000:03:00.0/iommu_group/type >> DMA-FQ >> >> # grep -i iommu /sys/kernel/debug/dri/*/i915_capabilities >> /sys/kernel/debug/dri/0/i915_capabilities:iommu: enabled >> /sys/kernel/debug/dri/1/i915_capabilities:iommu: enabled >> >> All good. >> >> intel_iommu=igfx_off >> -------------------- >> >> ## no dmar0 in sysfs >> # cat /sys/class/iommu/dmar2/devices/0000:03:00.0/iommu_group/type >> identity >> >> Unexpected!? >> >> # grep -i iommu /sys/kernel/debug/dri/*/i915_capabilities >> /sys/kernel/debug/dri/0/i915_capabilities:iommu: disabled >> /sys/kernel/debug/dri/1/i915_capabilities:iommu: disabled # At least >> the i915 patch detects it correctly. >> >> intel_iommu=off >> --------------- >> >> ## no dmar0 in sysfs >> ## no dmar2 in sysfs >> >> # grep -i iommu /sys/kernel/debug/dri/*/i915_capabilities >> /sys/kernel/debug/dri/0/i915_capabilities:iommu: disabled >> /sys/kernel/debug/dri/1/i915_capabilities:iommu: disabled >> >> All good. >> >> The fact discrete graphics changes from translated to pass-through >> when igfx_off is set is surprising to me. Is this a bug? > > The existing VT-d implementation doesn't distinguish igfx from dgfx. It > only checks whether the device is of a display class: > > #define IS_GFX_DEVICE(pdev) ((pdev->class >> 16) == PCI_BASE_CLASS_DISPLAY) > > When igfx_off is specified, all graphic devices will put into pass- > through (the same meaning as identity mapping) mode. For igfx, since > the iommu is always dedicated, hence it further turn off the iommu > (hence there's no iommu domain) to save power. Ah okay. Is this something we want to change/fix? Regards, Tvrtko