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[54.240.197.234]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48e3ebcb958sm23845574f8f.21.2026.10.27.08.47.15 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 27 Oct 2026 08:47:17 -0700 (PDT) From: Fred Griffoul To: Ackerley Tng , Paolo Bonzini , Sean Christopherson , Jason Gunthorpe , Kevin Tian Cc: Alex Williamson , Alexander Graf , Alexander Viro , Alexey Kardashevskiy , Andrew Morton , "Aneesh Kumar K . V" , Ashish Kalra , Baolin Wang , Baolu Lu , Bill Wendling , Borislav Petkov , Catalin Marinas , Christian Brauner , =?UTF-8?q?Christian=20K=C3=B6nig?= , Connor Williamson , Dave Hansen , Dave Jiang , David Hildenbrand , David Rientjes , David Woodhouse , Erdem Aktas , Frank van der Linden , Gregory Price , "H . Peter Anvin" , Hugh Dickins , Ingo Molnar , Jacob Pan , James Houghton , Jan Kara , Jianxiong Gao , Joerg Roedel , Joey Gouly , John Starks , Jonathan Corbet , Justin Stitt , Lorenzo Stoakes , Marc Zyngier , Michael Roth , Mike Rapoport , Nathan Chancellor , Nick Desaulniers , Nicolin Chen , Oliver Upton , Pratyush Yadav , Randy Dunlap , Robin Murphy , Samiullah Khawaja , Shuah Khan , Steffen Eiden , Steven Price , Suzuki K Poulose , Tarun Sahu , Thomas Gleixner , Tom Lendacky , Tycho Andersen , Vishal Annapurve , Vlastimil Babka , Will Deacon , Xu Yilun , Yan Zhao , Zenghui Yu , x86@kernel.org, Shuah Khan , Fuad Tabba , kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, iommu@lists.linux.dev Subject: [RFC PATCH 10/14] iommufd/selftest: Add mock-domain IOVA queries Date: Tue, 27 Oct 2026 15:46:45 +0000 Message-ID: <20261027154649.91571-11-griffoul@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261027154649.91571-1-griffoul@gmail.com> References: <20261022-gmem-alternative-providers-v2-0-5dd1dc6c660a@google.com> <20261027154649.91571-1-griffoul@gmail.com> X-Mailing-List: kvm@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Fred Griffoul Tests of guest_memfd mappings cannot know in advance which frame an IOVA reaches, since a revoke can unmap or replace it, and IOMMU_TEST_OP_MD_CHECK_MAP only compares a range against a user buffer. Add IOMMU_TEST_OP_MD_CHECK_MAPPED, which checks that a range of a mock domain is all mapped or all unmapped, and IOMMU_TEST_OP_MD_IOVA_TO_PHYS, which returns the physical address behind an IOVA. They hold domains_rwsem for writing, so that a userspace unmap cannot free a page-table level during the walk; they are not safe against a concurrent guest_memfd update or dma-buf revoke, which the selftests do not do. Assisted-by: Claude:claude-opus-5-5 Signed-off-by: Fred Griffoul --- drivers/iommu/iommufd/iommufd_test.h | 18 ++++ drivers/iommu/iommufd/selftest.c | 125 +++++++++++++++++++++++++++ 2 files changed, 143 insertions(+) diff --git a/drivers/iommu/iommufd/iommufd_test.h b/drivers/iommu/iommufd/iommufd_test.h index 52b78cbcc920..3fffcb2b20d7 100644 --- a/drivers/iommu/iommufd/iommufd_test.h +++ b/drivers/iommu/iommufd/iommufd_test.h @@ -31,6 +31,8 @@ enum { IOMMU_TEST_OP_PASID_CHECK_HWPT, IOMMU_TEST_OP_DMABUF_GET, IOMMU_TEST_OP_DMABUF_REVOKE, + IOMMU_TEST_OP_MD_CHECK_MAPPED, + IOMMU_TEST_OP_MD_IOVA_TO_PHYS, }; enum { @@ -193,6 +195,22 @@ struct iommu_test_cmd { __s32 dmabuf_fd; __u32 revoked; } dmabuf_revoke; + struct { + /* + * 1: every page in [iova, iova+length) must be mapped; + * 0: none of them may be. Any page in the other state + * fails with -ENOENT. Any other value, or a non-zero + * __reserved, is -EINVAL. + */ + __u32 mapped; + __u32 __reserved; + __aligned_u64 iova; + __aligned_u64 length; + } check_mapped; + struct { + __aligned_u64 iova; + __aligned_u64 out_phys; /* 0 if unmapped */ + } iova_to_phys; }; __u32 last; }; diff --git a/drivers/iommu/iommufd/selftest.c b/drivers/iommu/iommufd/selftest.c index ee706f18f7e9..378d7c46327e 100644 --- a/drivers/iommu/iommufd/selftest.c +++ b/drivers/iommu/iommufd/selftest.c @@ -2068,6 +2068,122 @@ static int iommufd_test_dmabuf_get(struct iommufd_ucmd *ucmd, return rc; } +/* + * True if [iova, iova + length) lies inside the domain's aperture. An IOVA + * that the domain cannot map would read as unmapped, so the queries refuse + * it rather than report it as such. + */ +static bool mock_domain_covers(struct mock_iommu_domain *mock, + unsigned long iova, size_t length) +{ + struct iommu_domain_geometry *geo = &mock->domain.geometry; + unsigned long last; + + if (check_add_overflow(iova, length - 1, &last)) + return false; + return iova >= geo->aperture_start && last <= geo->aperture_end; +} + +/* + * iova_to_phys() walks the page table, so it must not run while an unmap + * frees a level of it. A userspace unmap holds the IOAS domains_rwsem for + * reading while it unmaps the domains, so holding it for writing keeps such + * unmaps away. A guest_memfd update, e.g. on a conversion or a punch hole, + * and a dma-buf revoke unmap under their pages mutex only, so tests must not + * run these queries while one is in progress. A range can cross several + * areas and holes, so the queries take one IOAS-wide lock rather than the + * pages mutex of each area. + */ +static struct rw_semaphore * +mock_domain_unmap_lock(struct iommufd_hw_pagetable *hwpt) +{ + return &to_hwpt_paging(hwpt)->ioas->iopt.domains_rwsem; +} + +/* + * Report the physical address the mock domain resolves @iova to, or 0 if + * it is unmapped. Lets a test check that two IOVAs share one frame, or that + * an IOVA moved to another frame, without knowing the frames in advance. + * Not safe against a concurrent guest_memfd update or dma-buf revoke; see + * mock_domain_unmap_lock(). + */ +static int iommufd_test_md_iova_to_phys(struct iommufd_ucmd *ucmd, + unsigned int mockpt_id, + unsigned long iova) +{ + struct iommu_test_cmd *cmd = ucmd->cmd; + struct iommufd_hw_pagetable *hwpt; + struct mock_iommu_domain *mock; + unsigned int page_size; + int rc; + + hwpt = get_md_pagetable(ucmd, mockpt_id, &mock); + if (IS_ERR(hwpt)) + return PTR_ERR(hwpt); + + page_size = 1 << __ffs(mock->domain.pgsize_bitmap); + if (iova % page_size || !mock_domain_covers(mock, iova, page_size)) { + rc = -EINVAL; + goto out_put; + } + down_write(mock_domain_unmap_lock(hwpt)); + cmd->iova_to_phys.out_phys = + mock->domain.ops->iova_to_phys(&mock->domain, iova); + up_write(mock_domain_unmap_lock(hwpt)); + rc = iommufd_ucmd_respond(ucmd, sizeof(*cmd)); +out_put: + iommufd_put_object(ucmd->ictx, &hwpt->obj); + return rc; +} + +/* + * Check that [@iova, @iova + @length) is fully mapped or fully unmapped. Not + * safe against a concurrent guest_memfd update or dma-buf revoke; see + * mock_domain_unmap_lock(). + */ +static int iommufd_test_md_check_mapped(struct iommufd_ucmd *ucmd, + unsigned int mockpt_id, + unsigned long iova, size_t length, + u32 mapped, u32 reserved) +{ + struct iommufd_hw_pagetable *hwpt; + struct mock_iommu_domain *mock; + unsigned int page_size; + int rc = 0; + + if (mapped > 1 || reserved) + return -EINVAL; + + hwpt = get_md_pagetable(ucmd, mockpt_id, &mock); + if (IS_ERR(hwpt)) + return PTR_ERR(hwpt); + + page_size = 1 << __ffs(mock->domain.pgsize_bitmap); + if (iova % page_size || length % page_size || !length || + !mock_domain_covers(mock, iova, length)) { + rc = -EINVAL; + goto out_put; + } + + down_write(mock_domain_unmap_lock(hwpt)); + for (; length; length -= page_size, iova += page_size) { + bool is_mapped = + mock->domain.ops->iova_to_phys(&mock->domain, iova) != 0; + + if (is_mapped != mapped) { + rc = -ENOENT; + break; + } + /* A huge-page mock domain spans 2^38 bytes. */ + cond_resched(); + } + up_write(mock_domain_unmap_lock(hwpt)); + +out_put: + iommufd_put_object(ucmd->ictx, &hwpt->obj); + return rc; +} + static int iommufd_test_dmabuf_revoke(struct iommufd_ucmd *ucmd, int fd, bool revoked) { @@ -2180,6 +2296,15 @@ int iommufd_test(struct iommufd_ucmd *ucmd) return iommufd_test_dmabuf_revoke(ucmd, cmd->dmabuf_revoke.dmabuf_fd, cmd->dmabuf_revoke.revoked); + case IOMMU_TEST_OP_MD_CHECK_MAPPED: + return iommufd_test_md_check_mapped(ucmd, cmd->id, + cmd->check_mapped.iova, + cmd->check_mapped.length, + cmd->check_mapped.mapped, + cmd->check_mapped.__reserved); + case IOMMU_TEST_OP_MD_IOVA_TO_PHYS: + return iommufd_test_md_iova_to_phys(ucmd, cmd->id, + cmd->iova_to_phys.iova); default: return -EOPNOTSUPP; } -- 2.47.3