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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 10606EE14D0 for ; Thu, 7 Sep 2023 00:51:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233618AbjIGAv6 (ORCPT ); Wed, 6 Sep 2023 20:51:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56580 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229563AbjIGAv4 (ORCPT ); Wed, 6 Sep 2023 20:51:56 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9E12F173B for ; Wed, 6 Sep 2023 17:51:49 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id 3f1490d57ef6-d7eaffe2f99so424654276.2 for ; Wed, 06 Sep 2023 17:51:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1694047909; x=1694652709; darn=vger.kernel.org; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:from:to:cc:subject:date:message-id :reply-to; bh=yUH5GNhw6h16pTv/SpzxbMt0geRMFmR0znGoV0rGo/s=; b=EDMgIp2Fg8jZACCGABvIr2K81MQC09LDy6lRf3T5DFI9m+qNuKt1Ziq/p+WM7iIJTR l/Rxm+iVHkbIokiz6N2CnpuuOPVcV97DB1wcd08MNaBx2MQ1RIuvlPAXr/axB+brZs8T XcabSzLbl590ZaAEh0SQwcI5MIOVB4kJyLsTUcAGXPXZbENnk+NtAcAUW1fzYGMxs0sI M5YbPYKQxHnt0Ri89cgPPgS/xEIpSSe02NCO6wS9BJyDL1JojaYCX8zFRebTvcR9dpYG 2bB17uIrovhSq+3xYET+fYPhQ1T5wot2UrEP2Z13/vrue0qAh8zCSVUECr0KQp+FOPRb 1FUA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1694047909; x=1694652709; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=yUH5GNhw6h16pTv/SpzxbMt0geRMFmR0znGoV0rGo/s=; b=MMo/IaLdIFRXv/PtE8zdSL5109ZbfW8Ku6fGT5B7kOTYM/ufmnuAE7R9ZU7uH09adA sfeIxaLVkV/qBdEuX0p/m/iNfTga7HRnFbDromXsiV1E97f/EObwO5Ks/+W+eLSJBvo/ Xt4QTRY2swoaWnwhyklxz5w+fJfhtGDCeBkovFvdeVcHeARO+OGppfSys+Lyylr14Z9h SbqIQlQ0rC8vJRsH+Iv1zV88S6CXG37/m2eO5SXjIl0mIN5gUvjo27WyMSeFznPjXCcP FEXSItAOQTon/2K/kpWGM389JtdhSdJPDSXj8pBaWJkE5DxOugTkMAuOeYiwFgF7bpbe yqkw== X-Gm-Message-State: AOJu0Yw1t/Rkp56+pdmX+qbZGPEzEYYxXMVQU6Qqdm+PGqH/urq9qioc cVcAqsCTE5kK3H4m5wGsaB8wnxQmizE= X-Google-Smtp-Source: AGHT+IGDlXZ5S/hNR4V4bNTd9qDl20qc8uf02HVuD2eHTTh8dnaVoxZ7rW3Z9vSE4dEeiY92HUP8MRNFNec= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a25:2543:0:b0:d4d:8ade:4dfa with SMTP id l64-20020a252543000000b00d4d8ade4dfamr462429ybl.1.1694047908942; Wed, 06 Sep 2023 17:51:48 -0700 (PDT) Date: Wed, 6 Sep 2023 17:51:36 -0700 In-Reply-To: Mime-Version: 1.0 References: <20230808085056.14644-1-yan.y.zhao@intel.com> Message-ID: Subject: Re: [PATCH 0/2] KVM: x86/mmu: .change_pte() optimization in TDP MMU From: Sean Christopherson To: Paolo Bonzini Cc: Yan Zhao , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 07, 2023, Paolo Bonzini wrote: > On Tue, Sep 5, 2023 at 10:18=E2=80=AFPM Sean Christopherson wrote: > > Ooh, actually, maybe we could do > > > > static bool =3D !IS_ENABLED(CONFIG_KSM); > > > > and then cross our fingers that that doesn't regress some other funky s= etups. >=20 > It probably breaks gvisor-like setups that use MAP_PRIVATE mmap for > memslots? It would instantly break CoW even if memory is never > written. Doh, I completely forgot about gvisor and the like. Yan, I don't think this is worth pursuing. My understanding is that only l= egacy, relatively slow devices need DMA32. And as Robin pointed out, swiotlb=3Dfo= rce isn't something that's likely deployed and certainly isn't intended for performan= ce sensitive environments.