From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f45.google.com (mail-ed1-f45.google.com [209.85.208.45]) by sourceware.org (Postfix) with ESMTPS id 5A63D3858C27 for ; Wed, 31 Mar 2021 22:11:43 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 5A63D3858C27 Received: by mail-ed1-f45.google.com with SMTP id x21so24052125eds.4 for ; Wed, 31 Mar 2021 15:11:43 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Y2axwWxTL8XPpHwUo4AVE1zruv6RF5CEAUfc387i7Es=; b=HZwZhb/7MWy1h6t8WwtmXDuBnViN0/jYj3zAOYRSlAj3a5WUZnGg5PAmb5bIDTZzJ4 8IYOoblJ7OuD2W3Mc3eAcijaDsDBCoHvc26tYFWqYopbh7QcG8kEdRhCwEpAyePcZdZ8 oQyMlveWexFGb55JuP4kmhlx8Z0w2iaj3EhKohN631hflZYRbBt7CWtzhktuhH1D3zSU 7n9G8BT4saxtBhWN3QS72LpChCPvnbSF4nUxXv2O7b1oVKhVOlfFmWcg2CisP5jgKQwP 7CvVrwhJlMjxkbKwmNvIGSKxIHhkkDH4+mMy2auFOsIAmsXfyZTdn+Ce44e/KmG+4VRS vSUg== X-Gm-Message-State: AOAM533O4j180A86LEO3oCAFQIAm9zRspEebuaWUAi6tmRHa1fky0vXc bO7+hCN/MBQg3qIjnFTpp/sgF1FXIqLrS92kdAE= X-Google-Smtp-Source: ABdhPJxF0AoPasiOPUQ+0kRTOZRzhmrm9mBUogAT7SW0kIY9/mhNKnb1B9vGVs2u4pcp4dvBgMyrOrOTNlzbCilvdZs= X-Received: by 2002:aa7:d917:: with SMTP id a23mr6430206edr.122.1617228702378; Wed, 31 Mar 2021 15:11:42 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Len Brown Date: Wed, 31 Mar 2021 18:11:31 -0400 Message-ID: Subject: Re: Candidate Linux ABI for Intel AMX and hypothetical new related features To: robert@ocallahan.org Cc: Andy Lutomirski , David Laight , Dave Hansen , Andy Lutomirski , Greg KH , "Bae, Chang Seok" , X86 ML , LKML , libc-alpha , Florian Weimer , Rich Felker , Kyle Huey , Keno Fischer , Linux API Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00, FREEMAIL_ENVFROM_END_DIGIT, FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS, KAM_DMARC_STATUS, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=no autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 31 Mar 2021 22:11:44 -0000 On Wed, Mar 31, 2021 at 5:42 PM Robert O'Callahan wrote: > > For the record, the benefits of dynamic XCR0 for rr recording > portability still apply. I guess it'd be useful for CRIU too. We would > also benefit from anything that incentivizes increased support for > CPUID faulting. As previously mentioned, today we don't have an architectural way to trap a user into the kernel on CPUID, even though we can do this for a VMM. But spoofing CPUID isn't a solution to all problems. The feature really needs to be OFF to prevent users from using it, even if the supported mechanisms of discovering that feature say "NOT PRESENT". Today there are plenty of users who will opportunistically try everything in the cloud and choose the machine that allows them to do something that other machines will not -- even if it is not officially supported. If something is not enumerated, it really needs to also be turned off. cheers, --Len Brown, Intel Open Source Technology Center