From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-99.freemail.mail.aliyun.com (out30-99.freemail.mail.aliyun.com [115.124.30.99]) (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 6B3D4347C6 for ; Mon, 19 Oct 2026 03:25:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.99 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792380308; cv=none; b=L9a7SY9T/BZJBsibVCDMrxZ35SGaqL7SuTtmKMIo5TI5jBnydPR8Nn0ZzI8r9//0ghyYDIwr+zDOpRGtHHF7rigsotciu2aWoNAIZo8Hbv1vPvmHcZ85T7B/xzhktyaaS0C0HNSZMkAdbjIKcVvQeNqw4qqgBAHvWHiE1OlUxME= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792380308; c=relaxed/simple; bh=pHz7bBiMvgjVfQBo5baHnlnPFWb6vMs4JgxMC1w2pOA=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=nKJQidhCv/L9veggzQjajfAi2fwJltjF6Fr0vAmDXdL8p2fJEmZJo3gAaJdY+gxj5EeX2Wv6MvizFE7BwC2uboGpft+JPDjbgHugWK5tZhn5/r0U6wismjssdH0F2ZqHKW9vJxukoF2S33aFAQNBQ5WkDuJmaSlOryyw8bf6L4A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=puMxXBBz; arc=none smtp.client-ip=115.124.30.99 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="puMxXBBz" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1792380298; h=From:To:Subject:Date:Message-Id:MIME-Version; bh=29GF85zmWOT6R4wUdm9iWEGkKC6rqMmG98g3ZEC4smI=; b=puMxXBBzgTp7QfXL+yO1Ed0gSRWdoZQfaM3rWcTmMrHjbsDqf84fgG4jo6sYHzk7kzDX9Rn4zQmPQo9U79dxgwb3Pj5J6Pb+sQrXPeTR5fK2LVJlYQih7VJIxBGW+k2hzdQylssO5Sk0+E4U0M4JLjFKtTyRk5842lyemWBugmw= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R751e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033032089153;MF=fangyu.yu@linux.alibaba.com;NM=1;PH=DS;RN=12;SR=0;TI=SMTPD_---0XD-YOHi_1792380296; Received: from localhost.localdomain(mailfrom:fangyu.yu@linux.alibaba.com fp:SMTPD_---0XD-YOHi_1792380296 cluster:ay36) by smtp.aliyun-inc.com; Mon, 19 Oct 2026 11:24:57 +0800 From: fangyu.yu@linux.alibaba.com To: jgg@nvidia.com Cc: Ankit.Soni@amd.com, fangyu.yu@linux.alibaba.com, guoren@kernel.org, iommu@lists.linux.dev, joerg.roedel@amd.com, joro@8bytes.org, kevin.tian@intel.com, linux-kernel@vger.kernel.org, robin.murphy@arm.com, vasant.hegde@amd.com, will@kernel.org Subject: Re: [PATCH] iommupt/kunit: Read an exact NR_SECONDARY_PAGETABLE snapshot for the leak check Date: Mon, 19 Oct 2026 11:24:55 +0800 Message-Id: <20261019032455.36913-1-fangyu.yu@linux.alibaba.com> X-Mailer: git-send-email 2.39.3 (Apple Git-146) In-Reply-To: <20261016152343.GH13920@nvidia.com> References: <20261016152343.GH13920@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit >> >> +/* >> >> + * The global NR_SECONDARY_PAGETABLE counter is batched per-CPU and folded >> >> + * into the global value asynchronously, sum the global value and the per-CPU >> >> + * deltas to get an exact snapshot. >> >> + * >> >> + * The global value must be read without the clamp of global_node_page_state(): >> >> + * the raw counter is transiently negative whenever a folded free batch >> >> + * outweighs allocation deltas still pending on other CPUs, and clamping >> >> + * before adding the deltas back would overestimate and report phantom leaks. >> >> + * global_node_page_state_monotonic() is normally reserved for monotonic >> >> + * counters because a raw negative read is garbage as a page count, but the >> >> + * sum with the pending deltas always restores the exact non-negative value. >> >> + */ >> >> +static unsigned long pt_kunit_nr_secondary_pagetable(void) >> >> +{ >> >> + unsigned long nr = global_node_page_state_monotonic(NR_SECONDARY_PAGETABLE); >> >> + >> >> +#ifdef CONFIG_SMP >> >> + int nid, cpu; >> >> + >> >> + cpus_read_lock(); >> >> + for_each_online_cpu(cpu) >> >> + for_each_online_node(nid) >> >> + nr += per_cpu_ptr(NODE_DATA(nid)->per_cpu_nodestats, >> >> + cpu)->vm_node_stat_diff[NR_SECONDARY_PAGETABLE]; >> >> + cpus_read_unlock(); >> >> +#endif >> > >> >This should not be outside the mm code that manages this data >> >structure. >> > >> >> You're right. However, I couldn't find a way to solve this by >> modifying only the iommupt KUnit code. >> >> >I think the kunit runner executes this in some environment that >> >doesn't trigger this delay? At least I've never seen this assert? >> > >> >> I can reproduce the assert stably on an x86 machine by booting a >> 4-core riscv64 QEMU. > >Possibly kunit runner doesn't enable smp. Can you investigate? Maybe >we can solve this by disabling the check on !SMP > Hi Jason, I looked into this, and you're right: the default KUnit config does not enable SMP. All runs below were done on the current tree without the proposed fix. 1) Default KUnit command, without SMP - the tests pass: $ ./tools/testing/kunit/kunit.py run 'riscv_64_iommu*' \ --arch x86_64 --kunitconfig drivers/iommu/generic_pt The generated .config contains "# CONFIG_SMP is not set", and the run completes with: Testing complete. Ran 21 tests: passed: 18, skipped: 3 2) The same command with SMP enabled - the tests fail: $ ./tools/testing/kunit/kunit.py run 'riscv_64_iommu*' \ --arch x86_64 --kunitconfig drivers/iommu/generic_pt \ --kconfig_add CONFIG_SMP=y --qemu_args="-smp 4" The run fails consistently. In the example above, 14 of 21 tests failed. With the proposed fix, the same command passes with 18 passed and 3 skipped. 3) Could you clarify what you meant by "disabling the check on !SMP"? Thanks, Fangyu >Jason