Received: by 2002:a05:6a10:9848:0:0:0:0 with SMTP id x8csp888388pxf;
        Wed, 7 Apr 2021 14:12:30 -0700 (PDT)
X-Google-Smtp-Source: ABdhPJwiQizy+vkNGb9lLqpd3yxMfYnDIdySFuaLihicsu9sz4Wm4KYC+cCd2PpIPVHcHuoRR5rd
X-Received: by 2002:a17:906:170d:: with SMTP id c13mr5964180eje.491.1617829950570;
        Wed, 07 Apr 2021 14:12:30 -0700 (PDT)
ARC-Seal: i=1; a=rsa-sha256; t=1617829950; cv=none;
        d=google.com; s=arc-20160816;
        b=bWInx/NJ9a1kWo+TFW4OBODRnk8/12MJlXlQJJV/o4pMPRXRYARwHkNWaW3Pb/XvQc
         cceQX4C78pi6z0c6+aigTY5hqUMpobHeAP/9nYdgDB0T/2fPw8rd2Rk6ENkrw5QBI/7U
         RHRpkMAnNdI1Am2xIghiGL7wtK0mGFP/WopmjixDXtv06P7k8mKSA0sWW+qu6fUQ0FPh
         R3fVamBcj/FjHz5Gl/NrKe1/ydb770SxkMB6XUOIb+UloHlXatbzxKDs2t4EkZ/ZeCBh
         dc0f6gkeS5BgAvMR4fdCiQobX2HmudfAQ1ZJc47HaA6qt42j/wVd6p0Wn3gI3Ty8AoVK
         EJNw==
ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816;
        h=list-id:precedence:mime-version:user-agent:message-id:in-reply-to
         :date:references:subject:cc:to:from:ironport-sdr:ironport-sdr;
        bh=QnSgoChceNhzCJuoJ+CB2pAPgEsMYOg/X06kNrnd2o8=;
        b=Z++qKd4rHXNgHp+yhK/vVpyg6E9y0kSyZbRNIn+6c3cnFIBRtfxOrynSnRvMc2RLTA
         w8EDbcLulghVJ6zCJ3lha/lmL+PqZuVU9gMgs6yZ3bXFo/RAZBQphYixMitpQjSDcHMm
         HgRb5QLRIEl1SMBULbAJlX60b2+FY3I1Zt5bbq6wQQdkiyhDr2mF5vMHgIiurhBJOszI
         aYwKTiFhnpzY8CgQ0Io8Wrb9rM6d7NePFNVzeFLwvUdhkjZgn5T5Z4vu45cxwpk/uN5a
         xjN+RF+mTzR+uxWHKQ7ymX6qCPadG8FuNgugb+6OkXERV+0U6DCh3HsBvalInErCElOf
         388w==
ARC-Authentication-Results: i=1; mx.google.com;
       spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org;
       dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18])
        by mx.google.com with ESMTP id l11si20320601edb.511.2021.04.07.14.12.07;
        Wed, 07 Apr 2021 14:12:30 -0700 (PDT)
Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Authentication-Results: mx.google.com;
       spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org;
       dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S235055AbhDGPKu (ORCPT <rfc822;linuxmindflow@gmail.com>
        + 99 others); Wed, 7 Apr 2021 11:10:50 -0400
Received: from mga17.intel.com ([192.55.52.151]:11223 "EHLO mga17.intel.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S234763AbhDGPKt (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Wed, 7 Apr 2021 11:10:49 -0400
IronPort-SDR: vKTmazzJS8E0aS/6k/HuYd8lIT8k+SjLRkQwG/MMcrc6SJzqORTxVcwUc3BDPqtivhniaBmFOo
 spaTL0kfsIxA==
X-IronPort-AV: E=McAfee;i="6000,8403,9947"; a="173406785"
X-IronPort-AV: E=Sophos;i="5.82,203,1613462400"; 
   d="scan'208";a="173406785"
Received: from orsmga004.jf.intel.com ([10.7.209.38])
  by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Apr 2021 08:10:40 -0700
IronPort-SDR: Nh2sXErIvHnCufsdheEBQ6UWLhutJYLYv3s41okOLzye7V6PJUrqWrrsYr6rigFmkyppdLuIet
 kqmSSIH5M6BA==
X-ExtLoop1: 1
X-IronPort-AV: E=Sophos;i="5.82,203,1613462400"; 
   d="scan'208";a="530238532"
Received: from tassilo.jf.intel.com (HELO tassilo.localdomain) ([10.54.74.11])
  by orsmga004.jf.intel.com with ESMTP; 07 Apr 2021 08:10:40 -0700
Received: by tassilo.localdomain (Postfix, from userid 1000)
        id 0F76030027C; Wed,  7 Apr 2021 08:10:40 -0700 (PDT)
From:   Andi Kleen <ak@linux.intel.com>
To:     David Hildenbrand <david@redhat.com>
Cc:     "Kirill A. Shutemov" <kirill@shutemov.name>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Sean Christopherson <seanjc@google.com>,
        Jim Mattson <jmattson@google.com>,
        David Rientjes <rientjes@google.com>,
        "Edgecombe\, Rick P" <rick.p.edgecombe@intel.com>,
        "Kleen\, Andi" <andi.kleen@intel.com>,
        "Yamahata\, Isaku" <isaku.yamahata@intel.com>, x86@kernel.org,
        kvm@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Oscar Salvador <osalvador@suse.de>,
        Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Subject: Re: [RFCv1 7/7] KVM: unmap guest memory using poisoned pages
References: <20210402152645.26680-1-kirill.shutemov@linux.intel.com>
        <20210402152645.26680-8-kirill.shutemov@linux.intel.com>
        <5e934d94-414c-90de-c58e-34456e4ab1cf@redhat.com>
Date:   Wed, 07 Apr 2021 08:10:40 -0700
In-Reply-To: <5e934d94-414c-90de-c58e-34456e4ab1cf@redhat.com> (David
        Hildenbrand's message of "Wed, 7 Apr 2021 16:55:54 +0200")
Message-ID: <87v98yuo3z.fsf@linux.intel.com>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux)
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

David Hildenbrand <david@redhat.com> writes:

> I have no idea how expensive would be bouncing writes (and reads?)
> through the kernel. Did you ever experiment with that/evaluate that?

I would expect it to be quite expensive, as in virtio IO performance
tanking.

-Andi