From mboxrd@z Thu Jan 1 00:00:00 1970 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 91812C433EF for ; Thu, 5 May 2022 18:44:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1383090AbiEESrs (ORCPT ); Thu, 5 May 2022 14:47:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54740 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234429AbiEESrd (ORCPT ); Thu, 5 May 2022 14:47:33 -0400 Received: from mail-pg1-x52d.google.com (mail-pg1-x52d.google.com [IPv6:2607:f8b0:4864:20::52d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6EEDF12607 for ; Thu, 5 May 2022 11:38:13 -0700 (PDT) Received: by mail-pg1-x52d.google.com with SMTP id x12so4268188pgj.7 for ; Thu, 05 May 2022 11:38:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=h6f3As/+m4bLMms/WwsEXoQLRmJQOoNPDdbsWBcewj4=; b=qQb3iVumpLhy0QGvcH68nxEtLmyc/Tgcze+Y3k9udgQ851uac+wOQyMzBlFZ/ZtJ4q Hn5KV3KAP+kNIqG6gQbcQrclfNSA9rhWrgGyxICwwinFdRqAucMaIHXhv6drIZUE8ul3 c/pp+xv+9N0DPZTuicdMVSjDN+C5/Wzfg9lowRjvXOuWyLF/6RzGkhgG/tNgEjbKjKYb GiORfIqsmo5wMFN3nkDHXJ9RNOoIlUcQsV0oZg2hXBzdMvMxNR4ZuIRvY+usRfdFb9RY NQRqPVpe8LPlPHaL3PTOjlvPrff61lvT7exnWmLqb7K/otaFtJNCYWu/qBheDPgMRZOi i1bw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=h6f3As/+m4bLMms/WwsEXoQLRmJQOoNPDdbsWBcewj4=; b=EZmVQQUbNLTzcinNBvNn+IMtjdTmg1C5Z3gn3IkRT1yc5KQ1sRO7WvPTCMDW8jV6xi GXZD5e8pj7y7kqNjO1SSvnyTJKkBP3z++vSoNk7QKlOveA18ahHEsM5EZKOwLzaNQ+TL THz2BgsF0S7SCx6LuCcE1FJxxbSCWAnDAvERsewoaH42iX02R7IWIGNAk4Im1IBhMUTg scDnrTJPhJJ8v7fH8y92VcmIPZltQSxKCZ6iDjPrGyfDNUGHqnYUVW2lee9s0IzgV9+p 0WFjVFhLRcdfzgri54SI0fCzq+9ZHcHH1liSt7DX+wK7Z79FV00QZFOYvDZCihSOyBdu W7EQ== X-Gm-Message-State: AOAM533QM8Mahcdc4mzlCZkviSLgTk7QTmmZTof3F3t1Nb3aSQrI2v3A 4WY50iSlz2Z5G4xvOPMWC2XfkA== X-Google-Smtp-Source: ABdhPJx+VtpcHX0QHHvCgxGmpTR7ph4mOyzrSwp2YZH8AnXeJHKVLYUeNRBT+9CqmVRxJAORhAb6lA== X-Received: by 2002:a63:6cc5:0:b0:3ab:7a48:af2b with SMTP id h188-20020a636cc5000000b003ab7a48af2bmr23723065pgc.302.1651775892785; Thu, 05 May 2022 11:38:12 -0700 (PDT) Received: from google.com (157.214.185.35.bc.googleusercontent.com. [35.185.214.157]) by smtp.gmail.com with ESMTPSA id b7-20020aa79507000000b0050dc7628163sm1703433pfp.61.2022.05.05.11.38.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 May 2022 11:38:12 -0700 (PDT) Date: Thu, 5 May 2022 18:38:08 +0000 From: Sean Christopherson To: Ben Gardon Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Paolo Bonzini , Peter Xu , David Matlack , Jim Mattson , David Dunn , Jing Zhang , Junaid Shahid Subject: Re: [PATCH v7 05/11] KVM: selftests: Read binary stat data in lib Message-ID: References: <20220503183045.978509-1-bgardon@google.com> <20220503183045.978509-6-bgardon@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, May 05, 2022, Sean Christopherson wrote: > On Tue, May 03, 2022, Ben Gardon wrote: > Eww. I really, really hate code that asserts on a value and then returns that > same value. E.g. looking at just the declaration of read_stat_data() and the > change in stats_test(), I genuinely thought this patch dropped the assert. The > assert in vm_get_stat() also added to the confusion (I was reviewing that patch, > not this one). > > Rather than return the number of entries read, just assert that the number of > elements to be read is non-zero, then vm_get_stat() doesn't need to assert because > it'll be impossible to read anything but one entry without asserting. Ah, and __vm_get_stat() can do: for (i = 0; i < vm->stats_header.num_desc; ++i) { desc = get_stats_descriptor(vm->stats_desc, i, &vm->stats_header); if (strcmp(desc->name, stat_name)) continue; read_stat_data(vm->stats_fd, &vm->stats_header, desc, data, max_elements); return; } TEST_FAIL("Stat '%s' does not exist\n", stat_name); > > void read_stat_data(int stats_fd, struct kvm_stats_header *header, > struct kvm_stats_desc *desc, uint64_t *data, > size_t max_elements) > { > size_t nr_elements = min_t(size_t, desc->size, max_elements); > size_t size = nr_elements * sizeof(*data); > ssize_t ret; > > TEST_ASSERT(size, "No elements in stat '%s'", desc->name); > > ret = pread(stats_fd, data, size, header->data_offset + desc->offset); > > TEST_ASSERT(ret == size, > "pread() failed on stat '%s', wanted %lu bytes, got %ld", > desc->name, size, ret); Related to not printing a raw EINVAL (similar to above), it might be worth special casing the errno path, e.g. TEST_ASSERT(ret >= 0, "pread() failed on stat '%s', errno: %i (%s)", desc->name, errno, strerror(errno)); TEST_ASSERT(ret == size, "pread() on stat '%s' read %ld bytes, wanted %lu bytes", desc->name, size, ret);