From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E7CA84BCAA7; Thu, 7 May 2026 20:22:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778185373; cv=none; b=oAxeNy8aO3PB7nzVbPXufU7Kocz0aOE6kn9f+TnKdBNoa3H8D8ei5IG2j5//i4aJ49O0DMMC+fiUXAwjEnqg2ZIgn2VkaNzEjN67Uw+u9IxGZ0tNHRjzO2rflCcbw7y0EPgPOavL+75h7Lowp2OS+0MNQvN7b4mNjUZnCutA8eM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778185373; c=relaxed/simple; bh=i2DCByv5z1LmCb6d+0u3idii4v+I6xyhhA6Oey6vU1Y=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=N5BU3e7lwUjfR3lE/hV+RXvOuPgQafRvXOPx6G+hq/o2YZpDdBQ0TKroEnJejINYR1Zme05RA3i6CcroRAqLyxqiBw/D6C4usZYKzXem9i/FafevdNA+W8YMnrggUI3l6mQja5yYlXgxJRSzcD9By17LYZHxXHGSC43C7yQrUoo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=QrJASMqH; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="QrJASMqH" Received: by smtp.kernel.org (Postfix) with ESMTPS id BEEE1C4AF09; Thu, 7 May 2026 20:22:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778185372; bh=i2DCByv5z1LmCb6d+0u3idii4v+I6xyhhA6Oey6vU1Y=; h=From:Date:Subject:References:In-Reply-To:To:Cc:Reply-To:From; b=QrJASMqHiGB9kfyj44SZeKYIcKnp+Vc/bbiqM13IlvQc2M6WHqhq8gZEpMxUT8TsI 341nP1Ur81sVnLaPT08PkZmNjD0sDfDMxpOJN1z6ju7OZOI/Sb7ZlzEt1ycoBXvPa1 DtQONtq2eH/R485v9AoOhoge0CKR1xSEfBjOfcqLcfo3kX8obHo/HfAV1nuvza0qvO 2DGN6bZnmhWK1nl6Meqi2zv94KDJE4wOI2cjH2dQ6llznEzjUSPr2RqxOKxGn1/BTt N+5oTriVV17wIV8sjP00ypkK7x6oUQ6YyLIFzfy6j8+pJ6gm/QJJCrO4rBPcX/0Eg2 273wihSV7SrkQ== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id B150DCD37AA; Thu, 7 May 2026 20:22:52 +0000 (UTC) From: Ackerley Tng via B4 Relay Date: Thu, 07 May 2026 13:22:54 -0700 Subject: [PATCH v6 35/43] KVM: selftests: Test conversion with elevated page refcount Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260507-gmem-inplace-conversion-v6-35-91ab5a8b19a4@google.com> References: <20260507-gmem-inplace-conversion-v6-0-91ab5a8b19a4@google.com> In-Reply-To: <20260507-gmem-inplace-conversion-v6-0-91ab5a8b19a4@google.com> 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, ira.weiny@intel.com, 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, tabba@google.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 , Baoquan He , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Youngjun Park , Qi Zheng , Shakeel Butt , Kiryl Shutsemau , Jason Gunthorpe , 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 X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1778185365; l=3740; i=ackerleytng@google.com; s=20260225; h=from:subject:message-id; bh=ShebxFNR8cyYKJhqdsAuEPs4lv0Wp74neBFpE5OoHfk=; b=oGY6oGbsKFd03bkt91zRl6V9nz0Z0kJq6BalAUuo0PhX7ynYcZMAdcRPTk00X1HA2FWG22is5 Tb8i91J3ExLCt/zmSi/FFUcbyFlEyOIi8Y2aDRbzCTeE+/A3r3m3/hZ 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 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, for example via pin_user_pages(), the conversion must be aborted. This test uses vmsplice to increment the refcount of a specific page. The reference is kept on the page by not reading data out from vmsplice's destination pipe. It then attempts to convert a range of pages, including the page with elevated refcount, from shared to private. 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. Signed-off-by: Ackerley Tng Co-developed-by: Sean Christopherson Signed-off-by: Sean Christopherson --- .../kvm/x86/guest_memfd_conversions_test.c | 78 ++++++++++++++++++++++ 1 file changed, 78 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 4c33e21f04972..00a200a3019ef 100644 --- a/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c +++ b/tools/testing/selftests/kvm/x86/guest_memfd_conversions_test.c @@ -397,6 +397,84 @@ GMEM_CONVERSION_TEST_INIT_SHARED(forked_accesses) kvm_munmap(test_state, sizeof(*test_state)); } +static int pin_pipe[2] = { -1, -1 }; + +static void pin_pages(void *vaddr, size_t size) +{ + struct iovec iov = { + .iov_base = vaddr, + .iov_len = size, + }; + + if (pin_pipe[1] < 0) + TEST_ASSERT_EQ(pipe(pin_pipe), 0); + + TEST_ASSERT_EQ(vmsplice(pin_pipe[1], &iov, 1, 0), size); +} + +static void unpin_pages(void) +{ + close(pin_pipe[1]); + pin_pipe[1] = -1; + close(pin_pipe[0]); + pin_pipe[0] = -1; +} + +static void test_convert_to_private_fails(test_data_t *t, loff_t pgoff, + size_t nr_pages, + loff_t expected_error_offset) +{ + loff_t offset = pgoff * page_size; + loff_t error_offset = 0; + 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)); -- 2.54.0.563.g4f69b47b94-goog