From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mga12.intel.com (mga12.intel.com [192.55.52.136])
	(using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
	(No client certificate requested)
	by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8C54870
	for <linux-coco@lists.linux.dev>; Tue, 10 Aug 2021 17:52:07 +0000 (UTC)
X-IronPort-AV: E=McAfee;i="6200,9189,10072"; a="194546164"
X-IronPort-AV: E=Sophos;i="5.84,310,1620716400"; 
   d="scan'208";a="194546164"
Received: from orsmga004.jf.intel.com ([10.7.209.38])
  by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Aug 2021 10:52:06 -0700
X-ExtLoop1: 1
X-IronPort-AV: E=Sophos;i="5.84,310,1620716400"; 
   d="scan'208";a="570864967"
Received: from black.fi.intel.com ([10.237.72.28])
  by orsmga004.jf.intel.com with ESMTP; 10 Aug 2021 10:52:01 -0700
Received: by black.fi.intel.com (Postfix, from userid 1000)
	id 833FBF9; Tue, 10 Aug 2021 20:51:44 +0300 (EEST)
Date: Tue, 10 Aug 2021 20:51:44 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
	Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
	Sean Christopherson <seanjc@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Joerg Roedel <jroedel@suse.de>, Andi Kleen <ak@linux.intel.com>,
	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>,
	David Rientjes <rientjes@google.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Paolo Bonzini <pbonzini@redhat.com>, Ingo Molnar <mingo@redhat.com>,
	Varad Gautam <varad.gautam@suse.com>,
	Dario Faggioli <dfaggioli@suse.com>, x86@kernel.org,
	linux-mm@kvack.org, linux-coco@lists.linux.dev,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/5] x86: Impplement support for unaccepted memory
Message-ID: <20210810175144.uqlddcicyrweqb4j@black.fi.intel.com>
References: <20210810062626.1012-1-kirill.shutemov@linux.intel.com>
 <4b80289a-07a4-bf92-9946-b0a8afb27326@intel.com>
 <20210810151548.4exag5uj73bummsr@black.fi.intel.com>
 <82b8836f-a467-e5ff-08f3-704a85b9faa0@intel.com>
 <20210810173124.vzxpluaepdfe5aum@black.fi.intel.com>
 <51d9168c-ac14-0907-79b3-5d4dd46f92d6@intel.com>
Precedence: bulk
X-Mailing-List: linux-coco@lists.linux.dev
List-Id: <linux-coco.lists.linux.dev>
List-Subscribe: <mailto:linux-coco+subscribe@lists.linux.dev>
List-Unsubscribe: <mailto:linux-coco+unsubscribe@lists.linux.dev>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <51d9168c-ac14-0907-79b3-5d4dd46f92d6@intel.com>

On Tue, Aug 10, 2021 at 10:36:21AM -0700, Dave Hansen wrote:
> > The difference is going to be substantially lower once we get it optimized
> > properly.
> 
> What does this mean?  Is this future work in the kernel or somewhere in
> the TDX hardware/firmware which will speed things up?

Kernel has to be changed to accept memory in 2M and 1G chunks where
possible. The interface exists and described in spec, but not yet used in
guest kernel.

It would cut hypercall overhead dramatically. It makes upfront memory
accept more bearable and lowers latency of lazy memory accept. So I expect
the gap being not 20x, but like 3-5x (which is still huge).

-- 
 Kirill A. Shutemov