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b=BpmXdKz0XIvSVZ8GqSdXDQs2455zL23OpKCIwLlr15wvkZ1QTlC65RXK7BrAo+LhgNrmKNbzwaY8SdkHfA2x0l7L0vx2wuU7HlVYjynQCbjLcByTdlC3134pNpdjteIbyYY4Qs/HP7YIEgqNvX8DRegfhhh8WLKELsqdu9eYtMs= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from BL1PR12MB5754.namprd12.prod.outlook.com (2603:10b6:208:391::20) by MN2PR12MB4304.namprd12.prod.outlook.com (2603:10b6:208:1d0::12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9769.15; Mon, 30 Mar 2026 10:02:14 +0000 Received: from BL1PR12MB5754.namprd12.prod.outlook.com ([fe80::b080:4c1a:f6e5:4564]) by BL1PR12MB5754.namprd12.prod.outlook.com ([fe80::b080:4c1a:f6e5:4564%7]) with mapi id 15.20.9769.014; Mon, 30 Mar 2026 10:02:14 +0000 Message-ID: <294eb576-dcaf-45e2-bee5-558eaedc4a55@amd.com> Date: Mon, 30 Mar 2026 15:32:06 +0530 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] iommu/amd: add amd_iommu=relax_unity option for VFIO passthrough To: Christos Longros , Joerg Roedel Cc: Suravee Suthikulpanit , Will Deacon , Robin Murphy , Jonathan Corbet , Shuah Khan , iommu@lists.linux.dev, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260328213228.12084-1-chris.longros@gmail.com> Content-Language: en-US From: Vasant Hegde In-Reply-To: <20260328213228.12084-1-chris.longros@gmail.com> Content-Type: text/plain; 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The entries exist for platform devices like IOAPIC > and HPET, but they get applied to nearly every IOMMU group on the > system. Since commit a48ce36e2786 ("iommu: Prevent RESV_DIRECT > devices from blocking domains"), any device with IOMMU_RESV_DIRECT > regions has require_direct=1 set, which prevents VFIO from claiming > DMA ownership. I don't have client system handy to verify. Do you have acpi dump? I want to see IVMD flags are set. > > No PCI device can be passed through on affected boards -- not just > the platform devices that need the identity mappings, but also > endpoint devices like network adapters and GPUs. > > Intel handles a similar firmware over-specification with > device_rmrr_is_relaxable(), which marks certain RMRR entries as > IOMMU_RESV_DIRECT_RELAXABLE so VFIO can claim them. AMD has no > equivalent. May be we can do similar for pci devices instead of command line option? -Vasant