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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6606AC433EF for ; Wed, 20 Oct 2021 18:57:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4DF31610D0 for ; Wed, 20 Oct 2021 18:57:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231458AbhJTS75 (ORCPT ); Wed, 20 Oct 2021 14:59:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57604 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230076AbhJTS74 (ORCPT ); Wed, 20 Oct 2021 14:59:56 -0400 Received: from mail-pj1-x102d.google.com (mail-pj1-x102d.google.com [IPv6:2607:f8b0:4864:20::102d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CC797C06161C for ; Wed, 20 Oct 2021 11:57:41 -0700 (PDT) Received: by mail-pj1-x102d.google.com with SMTP id s61-20020a17090a69c300b0019f663cfcd1so1249970pjj.1 for ; Wed, 20 Oct 2021 11:57:41 -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=TvksdfctQPSKuZzYeC/pvdNqR1BvFx3obB1YwqOqH0c=; b=UUCVwojQK6iOOMJ0L1siU++CuwXPjXWsrIJs2r8AaeLfe5opibSmFTqvoavMS9rDIP MLgua2jERLSwvJHLmz/4DCAEi6VZ4Nk6uM8G9N0BoeXvtDKkWAOvF8jRixeiNPmBbijK 54ppKEbGr59EOTlkQOomxerFYpsvlGPa7EuTbwB77MLCzUQYv6rzT4h9SMDhQCgRQxZu ehNTRQ3W+Irl1KPVGY6xGx/t3IyURScB85UCGBLsfqijfdv55+Hgi88A8UQu4I3QCnJl RuS4xxFjfTQcXhSkr4KnMKYMqVONQL7xfb2bF8Dp3/g+waBimrpjrjUfi4LTg7CYdoUq ZwQg== 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=TvksdfctQPSKuZzYeC/pvdNqR1BvFx3obB1YwqOqH0c=; b=joojES9vVfcsTm75hKsrQxcvIyudtJ/WTiEZxAhh+pD1jCTsJECsKoni5LeVIEcyJ2 fwjXe9s2MwsKkoMdGBrfuUNDNZrkVMKwoqMpE1ImiK1h14ei79Dsedzi3ULYf4c29Kdl rS6TdOZYDm29fH9UvENxAqcfst8qWwixwHFD19bzdesO3BrtbKTHMHYpjLYi14FS+iYK GBJF/u0RKKvY/ehi8kSWywKj3/AjsISOlZ+/5lM7mGLGApUS4gj+K4fvamh+VTk4+Si/ 0O3d2v4/71ljPWBE5uhDHIRcM7mC3b6cX4XOG+ckY+UlEqHL9W1aPvD1r3nOu9HbWzPh EqbQ== X-Gm-Message-State: AOAM531ZMpWzVHWMgiYPMFHD6+vwLetwU3kTASpy3EXPbdbawJm1FHPp jDFCfec5ulu0RHLKweJy1xpiDA== X-Google-Smtp-Source: ABdhPJzDLaX0rT8jygcwV00K+SrPUQVwuAiJXVjXGIOFpcsdXoxMZABmhV6zUYF3vlOIU9g+BFBTnA== X-Received: by 2002:a17:902:be0f:b0:13a:95e:a51 with SMTP id r15-20020a170902be0f00b0013a095e0a51mr827571pls.44.1634756261166; Wed, 20 Oct 2021 11:57:41 -0700 (PDT) Received: from google.com (157.214.185.35.bc.googleusercontent.com. [35.185.214.157]) by smtp.gmail.com with ESMTPSA id z8sm3105052pgi.45.2021.10.20.11.57.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 Oct 2021 11:57:40 -0700 (PDT) Date: Wed, 20 Oct 2021 18:57:36 +0000 From: Sean Christopherson To: "Maciej S. Szmigiero" Cc: Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Igor Mammedov , Marc Zyngier , James Morse , Julien Thierry , Suzuki K Poulose , Huacai Chen , Aleksandar Markovic , Paul Mackerras , Christian Borntraeger , Janosch Frank , David Hildenbrand , Cornelia Huck , Claudio Imbrenda , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 07/13] KVM: Just resync arch fields when slots_arch_lock gets reacquired Message-ID: References: <311810ebd1111bed50d931d424297384171afc36.1632171479.git.maciej.szmigiero@oracle.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 Wed, Oct 20, 2021, Maciej S. Szmigiero wrote: > On 20.10.2021 01:55, Sean Christopherson wrote: > > On Mon, Sep 20, 2021, Maciej S. Szmigiero wrote: > > This should probably be a memcpy(), I don't know what all shenanigans the compiler > > can throw at us if it gets to copy a struct by value. > > Normally, copy-assignment of a struct is a safe operation (this is purely > an internal kernel struct, so there are no worries about padding leakage > to the userspace), but can replace this with a memcpy(). I was more worried about the compiler using SIMD instructions. I assume the kernel build process has lots of guards in place to prevent such shenanigans, but on the other hand I _know_ mempcy() is safe :-)