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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=1789084533; l=3126; i=ackerleytng@google.com; s=20260225; h=from:subject:message-id; bh=PmSTG3Mn3VeRBRB+Sk4c+WCKivO001+yahByLRYiXQc=; b=RpykbcULhzk4ajqe3DS/wC8n7+NFwOF0ACIKr+g2KTH4KaYSGPwwQkK/DSqTHRM2PdjRrrgAu Q3Hqr1m2V5LBan2oI5vKX8wYPbB8YSk5b4E/+D8Y4Rnch7JyaXKpDli 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: rspam08 X-Rspamd-Queue-Id: 7F5A8100006 X-Stat-Signature: bk14y9oqnpiyro8yksmccq1rfmpwb16f X-HE-Tag: 1789084553-94527 X-HE-Meta: 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 0iwxOToy PBrdPpJXAKPz876Z30kbAeK1yFJcmN39PYx2eAcL3LAE0bAUiNdsyhQfP8dIgvGI/BwANRNEORXzXdGec0fWY6u/yroZ4i4qcAtdV+fuOp/sS90LHuwVRpyiiDL8m2Y5Yv3V1svqjJatEkxg+D1wL4os13pSleOU4TnNIh6vH/lM2qujzJXAbZWZQFUQlh0u4dLNxTjl/4Ct2XXPxyVORUdnHUwyk6I5qDLUt2GyzVqBpePbke/poVRLp59wDk3J+x2Ar+qZzzKfPdVMrCfTIOuegZuN4jaUiHT7qY3Rdh/n6mTEPtHQxTjIiDKv2Tchf/E+jj3oO5QAugdqN4Nv0gr8BOFqjgU4l/5Kc+4lRR/HHaGIj8isRUD4XP8ur/ArQhqYvAsxcnhayGi/BRCqZlTbt5HRby1VfFRr52zJED3nkh4MqIwVWKUwzR42DH3CjIrKCI10uUxP7hkeNsBN/MjnkRiokloqN5U43 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 Signed-off-by: Ackerley Tng Tested-by: Shivank Garg Reviewed-by: Fuad Tabba --- .../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)); -- 2.55.0.1007.g17ff1f9808-goog