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CTRY:US; LANG:en; SCL:1; SRV:; IPV:CAL; SFV:NSPM; H:satlexmb07.amd.com; PTR:InfoDomainNonexistent; CAT:NONE; SFS:(13230040)(82310400026)(36860700013)(376014)(1800799024); DIR:OUT; SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Oct 2025 09:04:40.5488 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 75da3cb1-e3e8-481e-390b-08de0b00b583 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d; Ip=[165.204.84.17]; Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: DS3PEPF000099DF.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB4169 Received-SPF: permerror client-ip=2a01:111:f403:c005::5; envelope-from=Sairaj.ArunKodilkar@amd.com; helo=CO1PR03CU002.outbound.protection.outlook.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 10/13/2025 1:49 PM, Michael S. Tsirkin wrote: > On Mon, Oct 13, 2025 at 10:30:46AM +0530, Sairaj Kodilkar wrote: >> Physical AMD IOMMU supports up to 64 bits of DMA address. When device tries >> to read or write from a given DMA address, IOMMU translates the address >> using page table assigned to that device. Since IOMMU uses per device page >> tables, the emulated IOMMU should use the cache tag of 68 bits >> (64 bit address - 12 bit page alignment + 16 bit device ID). >> >> Current emulated AMD IOMMU uses GLib hash table to create software iotlb >> and uses 64 bit key to store the IOVA and deviceID, which limits the IOVA >> to 60 bits. This causes failure while setting up the device when guest is >> booted with "iommu.forcedac=1". >> >> To solve this problem, Use 64 bit IOVA and 16 bit devid as key to store >> entries in IOTLB; Use upper 52 bits of IOVA (GFN) and lower 12 bits of >> the device ID to construct the 64 bit hash key in order avoid the >> truncation as much as possible (reducing hash collisions). >> >> Fixes: d29a09ca6842 ("hw/i386: Introduce AMD IOMMU") >> Signed-off-by: Sairaj Kodilkar > I am wondering whether we need to limit how much host memory > can the shadow take. Because with so many bits, the sky is the limit ... > OTOH it's not directly caused by this patch, but it's something > we should think about maybe. I don't think I fully understand this. Do you mean the host memory taken by the pages used to build shadow page table ? > Something more to improve: > > >> --- >> hw/i386/amd_iommu.c | 57 ++++++++++++++++++++++++++++++--------------- >> hw/i386/amd_iommu.h | 4 ++-- >> 2 files changed, 40 insertions(+), 21 deletions(-) >> >> diff --git a/hw/i386/amd_iommu.c b/hw/i386/amd_iommu.c >> index b194e3294dd7..a218d147e53d 100644 >> --- a/hw/i386/amd_iommu.c >> +++ b/hw/i386/amd_iommu.c >> @@ -106,6 +106,11 @@ typedef struct amdvi_as_key { >> uint8_t devfn; >> } amdvi_as_key; >> >> +typedef struct amdvi_iotlb_key { >> + uint64_t gfn; >> + uint16_t devid; >> +} amdvi_iotlb_key; >> + > Pls change struct and typedef names to match qemu coding style. Thanks Sairaj