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b=P6YEZ4Bc0VeOMvPA1uk74Va73KyJ4xTftDeEp6LQB5OuVWayBasq+55tRM7ol0WHnt6HbQ/nlwJXodLWM6oElJw7q17dbmpo8rxLGDO/v0XnkYOw/QQ+OCCKz63t/xVXmDrHX40qAP/eBWTItewMoBBTO3lTxGhY2a+S+bWd2dQ= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from DS7PR12MB6048.namprd12.prod.outlook.com (2603:10b6:8:9f::5) by DM4PR12MB8499.namprd12.prod.outlook.com (2603:10b6:8:181::10) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.8769.29; Wed, 28 May 2025 12:19:44 +0000 Received: from DS7PR12MB6048.namprd12.prod.outlook.com ([fe80::6318:26e5:357a:74a5]) by DS7PR12MB6048.namprd12.prod.outlook.com ([fe80::6318:26e5:357a:74a5%4]) with mapi id 15.20.8769.022; Wed, 28 May 2025 12:19:44 +0000 Message-ID: <3b38fc9d-83c6-4db8-8a83-eb4265796b03@amd.com> Date: Wed, 28 May 2025 17:49:35 +0530 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] iommu/amd: Add HATDis feature support To: Ankit Soni , Joao Martins Cc: iommu@lists.linux.dev, suravee.suthikulpanit@amd.com, joro@8bytes.org, will@kernel.org, robin.murphy@arm.com, linux-kernel@vger.kernel.org, Alejandro Jimenez , David Woodhouse References: <6282a5c349812a311a67a8522dc5e4aabfe3ec3a.1745389415.git.Ankit.Soni@amd.com> <596ed125-c995-4e2b-824c-b7929c852754@oracle.com> <4f04d596-685e-4e48-9038-8aee6c927ebc@oracle.com> Content-Language: en-US From: Vasant Hegde In-Reply-To: Content-Type: text/plain; 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And in AMD case, HATDis bit indicates host(v1) translation is not >>>>> available, then attempt to use guest(v2) translation, and if both page >>>>> table modes are not available then disable dma tranlation. >>>> >>>> OK, I guess it makes sense if HATDis is v1 only. >>>> >>>> My other call out was that when we disable dma-translation all together (aka >>>> both modes), then we shouldn't advertise the IOMMU groups (internally and to >>>> userspace) by not calling iommu_device_register()/iommu_device_sysfs_add(). >>>> >>> >>> Sorry for the late reply. I had cross-checked it; if the probe fails, >>> then IOMMU groups will not be populated, and eventually, it will not >>> have significance for calling iommu_device_register()/iommu_device_sysfs_add(). >>> >> >> It would nonetheless populate a ivhd entry in sysfs needlessly but with an empty >> devices list (qemu diff at the tail end for how I checked it; it's only missing >> the ILLEGAL_DEVICE_TABLE_ENTRY event being generated, but enough to check the >> first patch with sw iommu) e.g. as far as I checked: >> >> $ find /sys | grep ivhd >> /sys/class/iommu/ivhd0 >> /sys/devices/pci0000:00/0000:00:05.0/iommu/ivhd0 >> /sys/devices/pci0000:00/0000:00:05.0/iommu/ivhd0/uevent >> /sys/devices/pci0000:00/0000:00:05.0/iommu/ivhd0/amd-iommu >> /sys/devices/pci0000:00/0000:00:05.0/iommu/ivhd0/amd-iommu/cap >> /sys/devices/pci0000:00/0000:00:05.0/iommu/ivhd0/amd-iommu/features >> /sys/devices/pci0000:00/0000:00:05.0/iommu/ivhd0/devices >> /sys/devices/pci0000:00/0000:00:05.0/iommu/ivhd0/device >> /sys/devices/pci0000:00/0000:00:05.0/iommu/ivhd0/subsystem >> > > I was assuming, since iommu is still active for interrupt remapping, > user may need info for cap and feature using /sys fs. > @vasant: can you please suggest on this? I don't have strong preference. But it looks like intel skips populating sysfs properties. May be we can match the behaviour and skip populating ivdh entries. -Vasant