From patchwork Wed Jan 8 18:43:54 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Daniel_P=2E_Berrang=C3=A9?= X-Patchwork-Id: 13931491 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 336EAE77199 for ; Wed, 8 Jan 2025 18:44:26 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tVb2F-0004Xd-JQ; Wed, 08 Jan 2025 13:44:07 -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 1tVb2A-0004XH-Cd for qemu-devel@nongnu.org; Wed, 08 Jan 2025 13:44:03 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tVb28-0005Rp-GQ for qemu-devel@nongnu.org; Wed, 08 Jan 2025 13:44:02 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1736361839; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=fNDO8QyZTltgSM+U61f3OccGA4jfTGddLKYMXWJS0yI=; b=cY//+yyrP+uLVzl9LKQYrjLXdcF28H7JCImai/fGVU99lLrHdqXRRl2tOj70ahmbtyH5GJ qcjg/87YUMAWmp4RrS/RuO6X80WFaAjPQYP7A5iWJ5rvsWbP/iuKOb9vyFWpEOcT8SkVWv M7DWWzGjZISdDplNLp5GTNEAHL1Yxn0= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-688-DFQff6zHPaCsfTxDqTF-5A-1; Wed, 08 Jan 2025 13:43:58 -0500 X-MC-Unique: DFQff6zHPaCsfTxDqTF-5A-1 X-Mimecast-MFC-AGG-ID: DFQff6zHPaCsfTxDqTF-5A Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id BA8D91944CEE for ; Wed, 8 Jan 2025 18:43:56 +0000 (UTC) Received: from toolbx.redhat.com (unknown [10.42.28.103]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 75F78300018D; Wed, 8 Jan 2025 18:43:55 +0000 (UTC) From: =?utf-8?q?Daniel_P=2E_Berrang=C3=A9?= To: qemu-devel@nongnu.org Cc: =?utf-8?q?Daniel_P=2E_Berrang=C3=A9?= , Thomas Huth , "Richard W.M. Jones" Subject: [PATCH] crypto: fix bogus error benchmarking pbkdf on fast machines Date: Wed, 8 Jan 2025 18:43:54 +0000 Message-ID: <20250108184354.997818-1-berrange@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.432, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 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 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 schedular. 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. Reported-by: Thomas Huth Reported-by: Richard W.M. Jones Signed-off-by: Daniel P. Berrangé Tested-by: Thomas Huth --- crypto/pbkdf.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/crypto/pbkdf.c b/crypto/pbkdf.c index 0dd7c3aeaa..b285958319 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 schedular + * 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;