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Peter Anvin" , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Jonathan Corbet , Shuah Khan , Shuah Khan , Vishal Annapurve , Andrew Morton , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Youngjun Park , Qi Zheng , Shakeel Butt , Kiryl Shutsemau , Baoquan He , Jason Gunthorpe , John Hubbard , Peter Xu , tarunsahu@google.com, Randy Dunlap , Lorenzo Stoakes , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jason Gunthorpe , Fuad Tabba , Vlastimil Babka , Baoquan He Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-coco@lists.linux.dev, Ackerley Tng X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1788135916; l=3125; i=ackerleytng@google.com; s=20260225; h=from:subject:message-id; bh=bdq0ORBWbWV6e+1Lwjwn03V1TzR8SfWSd/UMLobub+U=; b=NnP1BZbu0N94uPpRBk5CPXpMs+ccxDq0jjhSkfmKYKGqoRwJkG0Eihwb83HjkVPFK2YhDypLb uOdQzcWiUHlA8CmSmJnSj3ENMc7Qo9hZ3K2a+vP+fDkSUwboGAXmkC+ X-Developer-Key: i=ackerleytng@google.com; a=ed25519; pk=sAZDYXdm6Iz8FHitpHeFlCMXwabodTm7p8/3/8xUxuU= X-Endpoint-Received: by B4 Relay for ackerleytng@google.com/20260225 with auth_id=649 X-Original-From: Ackerley Tng Reply-To: ackerleytng@google.com X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: EE0F620003 X-Stat-Signature: 4s33bqoi6h33onwoa785kqcgy9nbith6 X-HE-Tag: 1788135941-377435 X-HE-Meta: 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 JnEgYDad Mie2qllq0/NSdJuEhuMMZzPKFOlwCk19W5d4vjD3mWRTX3CpmFiVSlPB86oz7t5WEsVs/TjOIaYZPo+wmdiPFIv5a23ZGN519/XZ7xYWIvm8Vsb3uwtg6UHtvCMr0IwPCmq4GkZlLRtIX1ht5cy9ta1xDafHzzDiCKq4Eq7WawFGufXfpTGh3ilVcPedxNGr6+RuAwVAX4HK1QXmijZw7pl2vApiU21N7OqJ2wGkcu3fYGM+E0UdFu6wu65yzLUEEX3z6FdrOPR4WYJhGYDeljU4t3u5KRc1TuIqH39L6G9TccxqPQFDFNeOcwLkjEbW0VEOKa6GORcqu0BfTB6eacRiJ2BhJQ9QW6JSs0SwEmr/mTh/2SgNnJzQXLGQnPNTY0kumFfaLfMbPKU8GgmorhjNo/xamNj7ZlOjpbyf9GvnZ5NMa0iXEKgONBWEWMR2r2PErmlcGimpUor3o5swCZ5D09XP6j/BGtN5q Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Ackerley Tng Add a selftest to verify that converting a shared guest_memfd page to a private page fails if the page has an elevated reference count. When KVM converts a shared page to a private one, it expects the page to have a reference count equal to the reference counts taken by the filemap. If another kernel subsystem holds a reference to the page, the conversion must be aborted. The test asserts that both bulk and single-page conversion attempts correctly fail with EAGAIN for the pinned page. After the page is unpinned, the test verifies that subsequent conversions succeed. Co-developed-by: Sean Christopherson Signed-off-by: Sean Christopherson Reviewed-by: Fuad Tabba Tested-by: Shivank Garg Signed-off-by: Ackerley Tng --- .../kvm/x86/guest_memfd_conversions_test.c | 56 ++++++++++++++++++++++ 1 file changed, 56 insertions(+) diff --git a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c index a972a09c5c6e5..e1c84df0f0596 100644 --- a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c +++ b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c @@ -444,6 +444,62 @@ GMEM_CONVERSION_TEST_INIT_SHARED(forked_accesses) #undef TEST_STATE_AWAIT } +static void test_convert_to_private_fails(test_data_t *t, u64 pgoff, + size_t nr_pages, + u64 expected_error_offset) +{ + /* +1 to make it anything but expected_error_offset. */ + u64 error_offset = expected_error_offset + 1; + u64 offset = pgoff * page_size; + int ret; + + do { + ret = __gmem_set_private(t->gmem_fd, offset, + nr_pages * page_size, &error_offset); + } while (ret == -1 && errno == EINTR); + TEST_ASSERT(ret == -1 && errno == EAGAIN, + "Wanted EAGAIN on page %lu, got %d (ret = %d)", pgoff, + errno, ret); + TEST_ASSERT_EQ(error_offset, expected_error_offset); +} + +GMEM_CONVERSION_MULTIPAGE_TEST_INIT_SHARED(elevated_refcount, 4) +{ + int i; + + pin_pages(t->mem + test_page * page_size, page_size); + + for (i = 0; i < nr_pages; i++) + test_shared(t, i, 0, 'A', 'B'); + + /* + * Converting in bulk should fail as long any page in the range has + * unexpected refcounts. + */ + test_convert_to_private_fails(t, 0, nr_pages, test_page * page_size); + + for (i = 0; i < nr_pages; i++) { + /* + * Converting page-wise should also fail as long any page in the + * range has unexpected refcounts. + */ + if (i == test_page) + test_convert_to_private_fails(t, i, 1, test_page * page_size); + else + test_convert_to_private(t, i, 'B', 'C'); + } + + unpin_pages(); + + gmem_set_private(t->gmem_fd, 0, nr_pages * page_size); + + for (i = 0; i < nr_pages; i++) { + char expected = i == test_page ? 'B' : 'C'; + + test_private(t, i, expected, 'D'); + } +} + int main(int argc, char *argv[]) { TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM)); -- 2.55.0.897.gb25b4bd76c-goog