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a=ed25519; pk=sAZDYXdm6Iz8FHitpHeFlCMXwabodTm7p8/3/8xUxuU= X-Developer-Signature: v=1; a=ed25519-sha256; t=1787735885; l=3125; i=ackerleytng@google.com; s=20260225; h=from:subject:message-id; bh=D4kSZoQjn2evbYJeBPXvMiB6VpABDixLKIO9Wkc0q2Y=; b=0Xl+Ft2JNeFgHc72cKdPUmlWIaaUKrTcWNaCuE5l4p0QjHUf+PDqPvln09IV5z3p6JgNwwSEQ MgPrgGhkueuDsaZhj/coMGB3BJHJjWnz0bwzPjys8Q0r27VmXRxCpWH X-Mailer: b4 0.16.0 Message-ID: <20260826-gmem-inplace-conversion-v11-38-0a15d8a799aa@google.com> Subject: [PATCH v11 38/46] KVM: selftests: Test conversion with elevated page refcount From: Ackerley Tng To: aik@amd.com, andrew.jones@linux.dev, binbin.wu@linux.intel.com, brauner@kernel.org, chao.p.peng@linux.intel.com, david@kernel.org, jmattson@google.com, jthoughton@google.com, michael.roth@amd.com, oupton@kernel.org, pankaj.gupta@amd.com, qperret@google.com, rick.p.edgecombe@intel.com, rientjes@google.com, shivankg@amd.com, steven.price@arm.com, willy@infradead.org, wyihan@google.com, yan.y.zhao@intel.com, forkloop@google.com, pratyush@kernel.org, suzuki.poulose@arm.com, aneesh.kumar@kernel.org, liam@infradead.org, Paolo Bonzini , Sean Christopherson , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. 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, Fuad Tabba , Vlastimil Babka 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 Content-Type: text/plain; charset="utf-8" X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 653AD1C0006 X-Stat-Signature: rky8gp51syjpbz95o9u6cirrzqqdm3p4 X-Rspam-User: X-HE-Tag: 1787735954-945038 X-HE-Meta: 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 vQh852xa 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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)); -- 2.55.0.887.g758fc8c411-goog