From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:55419)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <mtosatti@redhat.com>) id 1VZZTn-0004J9-JM
	for qemu-devel@nongnu.org; Fri, 25 Oct 2013 00:58:41 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <mtosatti@redhat.com>) id 1VZZTh-0006Lm-Jl
	for qemu-devel@nongnu.org; Fri, 25 Oct 2013 00:58:35 -0400
Received: from mx1.redhat.com ([209.132.183.28]:49660)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <mtosatti@redhat.com>) id 1VZZTh-0006Lf-C3
	for qemu-devel@nongnu.org; Fri, 25 Oct 2013 00:58:29 -0400
Received: from int-mx11.intmail.prod.int.phx2.redhat.com
	(int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24])
	by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r9P4wRSf023753
	(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK)
	for <qemu-devel@nongnu.org>; Fri, 25 Oct 2013 00:58:27 -0400
Date: Fri, 25 Oct 2013 02:58:05 -0200
From: Marcelo Tosatti <mtosatti@redhat.com>
Message-ID: <20131025045805.GA18280@amt.cnet>
References: <20131024211158.064049176@amt.cnet>
	<20131024211249.723543071@amt.cnet> <5269B378.6040409@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <5269B378.6040409@redhat.com>
Subject: Re: [Qemu-devel] [patch 2/2] i386: pc: align gpa<->hpa on 1GB
	boundary
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: aarcange@redhat.com, qemu-devel@nongnu.org, gleb@redhat.com

On Fri, Oct 25, 2013 at 12:55:36AM +0100, Paolo Bonzini wrote:
> > +        if (hpagesize == (1<<30)) {
> > +            unsigned long holesize = 0x100000000ULL - below_4g_mem_size;
> > +
> > +            memory_region_init_alias(ram_above_4g, NULL, "ram-above-4g", ram,
> > +                                    0x100000000ULL,
> > +                                    above_4g_mem_size - holesize);
> > +            memory_region_add_subregion(system_memory, 0x100000000ULL,
> > +                                    ram_above_4g);
> > +
> > +            ram_above_4g_piecetwo = g_malloc(sizeof(*ram_above_4g_piecetwo));
> > +            memory_region_init_alias(ram_above_4g_piecetwo, NULL,
> > +                                     "ram-above-4g-piecetwo", ram,
> > +                                     0x100000000ULL - holesize, holesize);
> > +            memory_region_add_subregion(system_memory,
> > +                                        0x100000000ULL +
> > +                                        above_4g_mem_size - holesize,
> > +                                        ram_above_4g_piecetwo);
> 
> Why break it in two?  You can just allocate extra holesize bytes in the
> "ram" MemoryRegion, and not map the part that corresponds to
> [0x100000000ULL - holesize, 0x100000000ULL).

- If the "ram" MemoryRegion is backed with 1GB hugepages, you might not 
want to allocate extra holesize bytes (which might require an entire
1GB page).

- 1GB backed RAM can be mapped with 2MB pages.

> Also, as Peter said this cannot depend on host considerations.  Just do
> it unconditionally, but only for new machine types (pc-1.8 and q35-1.8,
> since unfortunately we're too close to hard freeze).

Why the description of memory subregions and aliases are part of machine
types?