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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, Jason Gunthorpe , 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=1786139565; l=3125; i=ackerleytng@google.com; s=20260225; h=from:subject:message-id; bh=p2RZydKvg888n0XoOUjxbRa4guxOTSCM2qo+J0sXmYw=; b=jhnjesMtPkRy9w4qr83aPYgjzv9dcXLfod9ioti8LuuCqLHmGkcD+pPXy/JArMEhXvYNmQKjh s5ce18SW2lFA+PIFSNYHYakT4GaWXk1LNmCYqBn93k3nIj9DmABvRo8 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-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 013C11C0007 X-Rspam-User: X-Stat-Signature: i67dbnb1rddmr1bpsixcshzfewpxysqt X-HE-Tag: 1786139584-762872 X-HE-Meta: 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 yBntj4XA 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 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)); -- 2.55.0.654.g21b8a5bc05-goog