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 X-Spam-Level: X-Spam-Status: No, score=-7.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 16C69C43381 for ; Wed, 17 Mar 2021 11:26:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EEBF164F79 for ; Wed, 17 Mar 2021 11:26:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231351AbhCQL0U (ORCPT ); Wed, 17 Mar 2021 07:26:20 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:38162 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231400AbhCQLZ5 (ORCPT ); Wed, 17 Mar 2021 07:25:57 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1615980357; 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: in-reply-to:in-reply-to:references:references; bh=hf3ahyJnG7KBq8dYUu13erhwR3Va8RMaptoKSf/MrjA=; b=D1wMQk2AvOyZ//bnyqreifWGV83srYN4GllUdxt14pnwQse1hvgxS4H9Oz4/NQq7tuI4eN akAgNNwaJDx16f5t038UQ3We9a8LtU5t2KQ7X3WLAzfqDQEyd958bq/RCDyFBP25elAKuH JNf+r0tenLIq+uTX7GAC6D9Cr0JhoEs= Received: from mail-ed1-f70.google.com (mail-ed1-f70.google.com [209.85.208.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-502-JTVnN9TCPyq7cxbY9EW6dA-1; Wed, 17 Mar 2021 07:25:55 -0400 X-MC-Unique: JTVnN9TCPyq7cxbY9EW6dA-1 Received: by mail-ed1-f70.google.com with SMTP id cq11so19136762edb.14 for ; Wed, 17 Mar 2021 04:25:55 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=hf3ahyJnG7KBq8dYUu13erhwR3Va8RMaptoKSf/MrjA=; b=cg1OvNB1q1ydJ9c+d0+/kFJsTUVKyPCDDjhi+kmLxo+heQ/E/X8csKFNdEJThHUFss Bt4AMuY7iWHyu8PxoQg5mfpYtFXnBYi6GtypMf005QRoR9yAOS33ZtoS/rtrBAk26fM9 v5XH6yLvo94ewV0CskWV3N0vhZCybLkQiqHESzQD5qbAbw6tYOuF8DcXFLUZ+8ny4R4b TPFxwa3wbWgCIOElRzViCvM737JXuAYtRCYbA4f4lN/zVFOn9O7iy1COrGAEQJhn/kF0 w02QWKQ5eQuljn/5RaSM5JrGkcMeXkIxKEdIxCm8rt2DDxCEYBAddhTTYzNRUNNP2Mow NZTA== X-Gm-Message-State: AOAM533Wpp6HswRRZy0ylI1jyFx1QUOTRyz7FlB2S9AFba6oixX77a1w 2Q5rTKx/oVLFAYVDdmGTHWN+FbuyOjcFok0dKsSO3kkkOEda6aBNUJRUuVBdP8o/01lkNgQsw+p lIy9yGjGDU3zuRsZKi+sHfsCt X-Received: by 2002:aa7:cd63:: with SMTP id ca3mr41862733edb.265.1615980354313; Wed, 17 Mar 2021 04:25:54 -0700 (PDT) X-Google-Smtp-Source: ABdhPJx542/MtHcjVj7T6Y1o987zHhETplS0SvtnlCENkTe2wcSrH1QkY3UECfjJKv/OX6Yb9NTx+Q== X-Received: by 2002:aa7:cd63:: with SMTP id ca3mr41862719edb.265.1615980354183; Wed, 17 Mar 2021 04:25:54 -0700 (PDT) Received: from localhost.localdomain ([194.230.155.192]) by smtp.gmail.com with ESMTPSA id s20sm11264312ejj.38.2021.03.17.04.25.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 17 Mar 2021 04:25:53 -0700 (PDT) Subject: Re: [PATCH] selftests/kvm: add test for KVM_GET_MSR_FEATURE_INDEX_LIST To: Paolo Bonzini , linux-kselftest@vger.kernel.org Cc: Shuah Khan , Vitaly Kuznetsov , Andrew Jones , linux-kernel@vger.kernel.org, kvm@vger.kernel.org References: <20210317074552.8550-1-eesposit@redhat.com> From: Emanuele Giuseppe Esposito Message-ID: <61d11f32-a2da-b593-1c62-bbadc6408215@redhat.com> Date: Wed, 17 Mar 2021 12:25:52 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 17/03/2021 11:49, Paolo Bonzini wrote: > On 17/03/21 08:45, Emanuele Giuseppe Esposito wrote: >> +    struct kvm_msr_list features_list; >>       buffer.header.nmsrs = 1; >>       buffer.entry.index = msr_index; >> +    features_list.nmsrs = 1; >> + >>       kvm_fd = open(KVM_DEV_PATH, O_RDONLY); >>       if (kvm_fd < 0) >>           exit(KSFT_SKIP); >> +    r = ioctl(kvm_fd, KVM_GET_MSR_FEATURE_INDEX_LIST, &features_list); >> +    TEST_ASSERT(r < 0 && r != -E2BIG, "KVM_GET_MSR_FEATURE_INDEX_LIST >> IOCTL failed,\n" >> +        "  rc: %i errno: %i", r, errno); > > Careful: because this has nsmrs == 1, you are overwriting an u32 of the > stack after struct kvm_msr_list.  You need to use your own struct > similar to what is done with "buffer.header" and "buffer.entry". > >>       r = ioctl(kvm_fd, KVM_GET_MSRS, &buffer.header); >>       TEST_ASSERT(r == 1, "KVM_GET_MSRS IOCTL failed,\n" >>           "  rc: %i errno: %i", r, errno); >> > > More in general, this is not a test, but rather a library function used > to read a single MSR. > > If you would like to add a test for KVM_GET_MSR_FEATURE_INDEX_LIST that > would be very welcome.  That would be a new executable.  Looking at the > logic for the ioctl, the main purpose of the test should be: > > - check that if features_list.nmsrs is too small it will set the nmsrs > field and return -E2BIG. > > - check that all MSRs returned by KVM_GET_MSR_FEATURE_INDEX_LIST can be > accessed with KVM_GET_MSRS > > So something like this: > >   set nmsrs to 0 and try the ioctl >   check that it returns -E2BIG and has changed nmsrs >   if nmsrs != 1 { >     set nmsrs to 1 and try the ioctl again >     check that it returns -E2BIG >   } >   malloc a buffer with room for struct kvm_msr_list and nmsrs indices >   set nmsrs in the malloc-ed buffer and try the ioctl again >   for each index >     invoke kvm_get_feature_msr to read it > > (The test should also be skipped if KVM does not expose the > KVM_CAP_GET_MSR_FEATURES capability). Thank you for the feedback, the title is indeed a little bit misleading. My idea in this patch was to just add an additional check to all usages of KVM_GET_MSRS, since KVM_GET_MSR_FEATURE_INDEX_LIST is used only to probe host capabilities and processor features. But you are right, a separate test would be better. Thank you, Emanuele