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=-8.0 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 5429CC4338F for ; Mon, 2 Aug 2021 16:53:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3798A610A2 for ; Mon, 2 Aug 2021 16:53:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232985AbhHBQxK (ORCPT ); Mon, 2 Aug 2021 12:53:10 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:57971 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229945AbhHBQxJ (ORCPT ); Mon, 2 Aug 2021 12:53:09 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1627923179; 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=/5yXRDtcxx+lYhsKMFvTyTWw4OOI/miYLG3qItS8RDg=; b=acrFbOQzwo3Wv3VT0uUJZIvGVIk560VO+aM8bmWrlYMfaFzSQbs/sRPrOzHbApfOwCSd84 oBTGMVb54qQu+SA9KBUHk1HYet9bMAM2+8f7ZaxWsYSqoB4cXscEmlKhrXWNYr0glnINRF l8E2HNqXD20B6EFQdUXVKycfIOsyYwk= Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-234-MinoYQ_CMba6ulwNi3uV0g-1; Mon, 02 Aug 2021 12:52:58 -0400 X-MC-Unique: MinoYQ_CMba6ulwNi3uV0g-1 Received: by mail-wr1-f72.google.com with SMTP id a9-20020a0560000509b029015485b95d0cso1107378wrf.5 for ; Mon, 02 Aug 2021 09:52:57 -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=/5yXRDtcxx+lYhsKMFvTyTWw4OOI/miYLG3qItS8RDg=; b=HSN4MF7l/Nx6BVnIOz/DXM8etV5oAuIn1hbn6y6oaMVRUhu5A1RKlNN+npg4n7nG6o p9jPS/LYwFkvGWer/3eVOU91k3p+V3YVh8Xv+7zN59IWD/W30tdnrxn/1y2AExhXiewW zzv8+DIVZuhuYS1XWcg6qoLrHD7ukLCcF5h6qRGupbzCECuUh4UH4xI4J4OgvR9BAYCJ rBhyMlUiKfWAx7HGeWMYrqL1TNFClIZ/MvqCC4/TiKY8E+FyPfVxflMn3B429aP0Rnwd XiTzp8I28/1po9NHFB25iYT8u/e1Np+1iEgL6EGL21v2s7atyV1Ks01pRta/XFvhcZO7 VV2Q== X-Gm-Message-State: AOAM530Poklqk3wBCtYJGIN76jZ7vs81d4WQgLyttspiUl4FLiFP+EIJ 4iYYE65W9zRD0mOpih8GdIRiUaKba1n65FjFPzVCoHJ5pC2ime20FDokvbPN/3KeiRyu6bbTziG EgR9sxhsD9WL4Zqk4a9s77RMr X-Received: by 2002:a5d:6184:: with SMTP id j4mr18889841wru.340.1627923176987; Mon, 02 Aug 2021 09:52:56 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzvhdCH2/tdqYCOMdRGFxIAzLd6brKr14f5SN7rUeCEDiOZsk0qTjmq/kSRJTHoau6cfGf9AQ== X-Received: by 2002:a5d:6184:: with SMTP id j4mr18889829wru.340.1627923176813; Mon, 02 Aug 2021 09:52:56 -0700 (PDT) Received: from ?IPv6:2001:b07:6468:f312:c8dd:75d4:99ab:290a? ([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id u11sm12164787wrt.89.2021.08.02.09.52.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 02 Aug 2021 09:52:56 -0700 (PDT) Subject: Re: [PATCH] KVM: SEV: improve the code readability for ASID management To: Sean Christopherson , Mingwei Zhang Cc: Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Tom Lendacky , Marc Orr , David Rientjes , Alper Gun , Dionna Glaze , Vipin Sharma References: <20210731011304.3868795-1-mizhang@google.com> From: Paolo Bonzini Message-ID: <71a905a1-0a6f-0d7a-f8fe-237b9e5af05c@redhat.com> Date: Mon, 2 Aug 2021 18:52:54 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/08/21 18:17, Sean Christopherson wrote: > > Rather than adjusting the bitmap index, what about simply umping the bitmap size? > IIRC, current CPUs have 512 ASIDs, counting ASID 0, i.e. bumping the size won't > consume any additional memory. And if it does, the cost is 8 bytes... > > It'd be a bigger refactoring, but it should completely eliminate the mod-by-1 > shenanigans, e.g. a partial patch could look like This is also okay by me if Mingwei agrees, of course. I have already queued his patch, but I can replace it with one using a nr_asids-sized bitmap too. Paolo