From patchwork Mon Jan 27 14:17:55 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Michael Tokarev X-Patchwork-Id: 13951511 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 1DDBEC02188 for ; Mon, 27 Jan 2025 14:30:55 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tcQ5P-0001Sc-4E; Mon, 27 Jan 2025 09:27:37 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tcQ58-0000o3-1t; Mon, 27 Jan 2025 09:27:18 -0500 Received: from isrv.corpit.ru ([86.62.121.231]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tcQ56-0003Pq-Ao; Mon, 27 Jan 2025 09:27:17 -0500 Received: from localhost.tls.msk.ru (mjt.wg.tls.msk.ru [192.168.177.130]) by isrv.corpit.ru (Postfix) with ESMTP id F1AF4E0F98; Mon, 27 Jan 2025 17:26:46 +0300 (MSK) Received: by localhost.tls.msk.ru (Postfix, from userid 1000) id BE6A851DB7; Mon, 27 Jan 2025 17:18:03 +0300 (MSK) From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, =?utf-8?q?Daniel_P=2E_Berrang=C3=A9?= , Thomas Huth , "Richard W . M . Jones" , Michael Tokarev Subject: [Stable-9.2.1 41/41] crypto: fix bogus error benchmarking pbkdf on fast machines Date: Mon, 27 Jan 2025 17:17:55 +0300 Message-Id: <20250127141803.3514882-41-mjt@tls.msk.ru> X-Mailer: git-send-email 2.39.5 In-Reply-To: References: MIME-Version: 1.0 Received-SPF: pass client-ip=86.62.121.231; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-Spam_score_int: -68 X-Spam_score: -6.9 X-Spam_bar: ------ X-Spam_report: (-6.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_HI=-5, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: Daniel P. Berrangé We're seeing periodic reports of errors like: $ qemu-img create -f luks --object secret,data=123456,id=sec0 \ -o key-secret=sec0 luks-info.img 1M Formatting 'luks-info.img', fmt=luks size=1048576 key-secret=sec0 qemu-img: luks-info.img: Unable to get accurate CPU usage This error message comes from a recent attempt to workaround a kernel bug with measuring rusage in long running processes: commit c72cab5ad9f849bbcfcf4be7952b8b8946cc626e Author: Tiago Pasqualini Date: Wed Sep 4 20:52:30 2024 -0300 crypto: run qcrypto_pbkdf2_count_iters in a new thread Unfortunately this has a subtle bug on machines which are very fast. On the first time around the loop, the 'iterations' value is quite small (1 << 15), and so will run quite fast. Testing has shown that some machines can complete this benchmarking task in as little as 7 milliseconds. Unfortunately the 'getrusage' data is not updated at the time of the 'getrusage' call, it is done asynchronously by the scheduler. The 7 millisecond completion time for the benchmark is short enough that 'getrusage' sometimes reports 0 accumulated execution time. As a result the 'delay_ms == 0' sanity check in the above commit is triggering non-deterministically on such machines. The benchmarking loop intended to run multiple times, increasing the 'iterations' value until the benchmark ran for > 500 ms, but the sanity check doesn't allow this to happen. To fix it, we keep a loop counter and only run the sanity check after we've been around the loop more than 5 times. At that point the 'iterations' value is high enough that even with infrequent updates of 'getrusage' accounting data on fast machines, we should see a non-zero value. Fixes: https://lore.kernel.org/qemu-devel/ffe542bb-310c-4616-b0ca-13182f849fd1@redhat.com/ Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=2336437 Reported-by: Thomas Huth Reported-by: Richard W.M. Jones Tested-by: Thomas Huth Signed-off-by: Daniel P. Berrangé Message-ID: <20250109093746.1216300-1-berrange@redhat.com> Signed-off-by: Thomas Huth (cherry picked from commit 145f12ea885c8fcfbe2d0ac5230630f071b5a9fb) Signed-off-by: Michael Tokarev diff --git a/crypto/pbkdf.c b/crypto/pbkdf.c index 0dd7c3aeaa..2989fc0a40 100644 --- a/crypto/pbkdf.c +++ b/crypto/pbkdf.c @@ -107,7 +107,7 @@ static void *threaded_qcrypto_pbkdf2_count_iters(void *data) size_t nsalt = iters_data->nsalt; size_t nout = iters_data->nout; Error **errp = iters_data->errp; - + size_t scaled = 0; uint64_t ret = -1; g_autofree uint8_t *out = g_new(uint8_t, nout); uint64_t iterations = (1 << 15); @@ -131,7 +131,17 @@ static void *threaded_qcrypto_pbkdf2_count_iters(void *data) delta_ms = end_ms - start_ms; - if (delta_ms == 0) { /* sanity check */ + /* + * For very small 'iterations' values, CPU (or crypto + * accelerator) might be fast enough that the scheduler + * hasn't incremented getrusage() data, or incremented + * it by a very small amount, resulting in delta_ms == 0. + * Once we've scaled 'iterations' x10, 5 times, we really + * should be seeing delta_ms != 0, so sanity check at + * that point. + */ + if (scaled > 5 && + delta_ms == 0) { /* sanity check */ error_setg(errp, "Unable to get accurate CPU usage"); goto cleanup; } else if (delta_ms > 500) { @@ -141,6 +151,7 @@ static void *threaded_qcrypto_pbkdf2_count_iters(void *data) } else { iterations = (iterations * 1000 / delta_ms); } + scaled++; } iterations = iterations * 1000 / delta_ms;