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=-3.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 9CEBFC352A4 for ; Fri, 7 Feb 2020 09:29:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 70E1420726 for ; Fri, 7 Feb 2020 09:29:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="O96wtdxb" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727028AbgBGJ3W (ORCPT ); Fri, 7 Feb 2020 04:29:22 -0500 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:28841 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726798AbgBGJ3W (ORCPT ); Fri, 7 Feb 2020 04:29:22 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1581067761; 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: in-reply-to:in-reply-to:references:references; bh=iOOYHtkvRPysCVjAW2MS9yml97iZ6MtUp4OwxVIj6eU=; b=O96wtdxbtSDwlMdADmzErnVDWS4/9U26LZGLAvh6NZkWaC/E3RlPg8SbZ5wDhfDyE//+uT UqVe5DyOZs72pc9JMRWsL/V4tqgsBezx5heHGV+VjuW6TWRZBWl1+zWLn0MxtgJpiAtQgl HxEJHgL5z/ph+i0UMP5xL38RLYzokKY= 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-311-4AD0fUrYPmqTrUXBVN9Kww-1; Fri, 07 Feb 2020 04:29:19 -0500 X-MC-Unique: 4AD0fUrYPmqTrUXBVN9Kww-1 Received: by mail-wr1-f72.google.com with SMTP id x15so946126wrl.15 for ; Fri, 07 Feb 2020 01:29:18 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:in-reply-to:references:date :message-id:mime-version; bh=iOOYHtkvRPysCVjAW2MS9yml97iZ6MtUp4OwxVIj6eU=; b=U35XjWrrxKmOdyCwsMwgnaEoUsZNTRaCgsuwohrSrVeLxcfTrHgodUPGdihblWFDzY bwBfMQtNDvuTPPgywMyjClIcaXsRnixivtCOGx55UbBzZAUrlU/nB0uK4qgrC75wvw3h TQrovvlOOYlv5WBL5ywv4wp+TcExUK7FMMlZqw1plTDza3MH1BqxPVeHZAcq2FJHuctQ K8OTrAOaq7+0Jy98JCc9ivdSDBRnVLkOZrVvCL/d1SnI7oiOYLYtmot+R23OXqodEdO/ DN+23XbXXrtsUzh4Vdw7ZCVulVONfChokRkKdwCk8iLxnIUAdbLDDY9T16dWdl9Ppt6+ roOQ== X-Gm-Message-State: APjAAAUyzlcE859sbrNC5pn3knFw8MGOw9o4qPWgm1OBKtQ2iWU2roHj trUu2+ilg/Z4KSvfzSoBeXPKdgJ3F4W3C1teQ/J2Hsd/Kb98wkc4XQ+q0aKL3tx8DCNPWRqia8H 3mFpyrAhBtGe4GGiNtQ8nh9QJ X-Received: by 2002:adf:b193:: with SMTP id q19mr3640664wra.78.1581067757722; Fri, 07 Feb 2020 01:29:17 -0800 (PST) X-Google-Smtp-Source: APXvYqx52CMjinFmLJOvrK2em63PNSJWTz7pU6FQlu7AlGQ+F6sZ8fFrI8mL3eJCa7Fib456Wxes2A== X-Received: by 2002:adf:b193:: with SMTP id q19mr3640645wra.78.1581067757491; Fri, 07 Feb 2020 01:29:17 -0800 (PST) Received: from vitty.brq.redhat.com (nat-pool-brq-t.redhat.com. [213.175.37.10]) by smtp.gmail.com with ESMTPSA id u4sm2599245wrt.37.2020.02.07.01.29.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 07 Feb 2020 01:29:16 -0800 (PST) From: Vitaly Kuznetsov To: Sean Christopherson Cc: Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Paolo Bonzini Subject: Re: [PATCH] KVM: x86/mmu: Avoid retpoline on ->page_fault() with TDP In-Reply-To: <20200206221434.23790-1-sean.j.christopherson@intel.com> References: <20200206221434.23790-1-sean.j.christopherson@intel.com> Date: Fri, 07 Feb 2020 10:29:16 +0100 Message-ID: <878sleg2z7.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Sean Christopherson writes: > Wrap calls to ->page_fault() with a small shim to directly invoke the > TDP fault handler when the kernel is using retpolines and TDP is being > used. Denote the TDP fault handler by nullifying mmu->page_fault, and > annotate the TDP path as likely to coerce the compiler into preferring > the TDP path. > > Rename tdp_page_fault() to kvm_tdp_page_fault() as it's exposed outside > of mmu.c to allow inlining the shim. > > Signed-off-by: Sean Christopherson > --- Out of pure curiosity, if we do something like if (vcpu->arch.mmu->page_fault == tdp_page_fault) tdp_page_fault(...) else if (vcpu->arch.mmu->page_fault == nonpaging_page_fault) nonpaging_page_fault(...) ... we also defeat the retpoline, right? Should we use this technique ... everywhere? :-) -- Vitaly