linux-kernel - Re: [PATCH v3 08/10] xen: use host E820 map for dom0

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Date:	Tue, 19 Oct 2010 11:49:41 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Stefano Stabellini <Stefano.Stabellini@...citrix.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	Jeremy Fitzhardinge <Jeremy.Fitzhardinge@...rix.com>,
	Ian Campbell <Ian.Campbell@...citrix.com>
Subject: Re: [PATCH v3 08/10] xen: use host E820 map for dom0

On Mon, 18 Oct 2010, Konrad Rzeszutek Wilk wrote:
> On Tue, Oct 12, 2010 at 05:42:48PM +0100, Stefano Stabellini wrote:
> > From: Ian Campbell <ian.campbell@...rix.com>
> > 
> > When running as initial domain, get the real physical memory map from
> > xen using the XENMEM_machine_memory_map hypercall and use it to setup
> > the e820 regions.
> > 
> > Signed-off-by: Ian Campbell <ian.campbell@...rix.com>
> > Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
> > ---
> >  arch/x86/xen/setup.c           |   43 +++++++++++++++++++++++++++++++++++++--
> >  include/xen/interface/memory.h |   28 ++++++++++++++++++++++++++
> >  2 files changed, 68 insertions(+), 3 deletions(-)
> > 
> > diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
> > index 62ceb78..b08aac2 100644
> > --- a/arch/x86/xen/setup.c
> > +++ b/arch/x86/xen/setup.c
> > @@ -107,14 +107,51 @@ static unsigned long __init xen_return_unused_memory(unsigned long max_pfn,
> >  
> >  char * __init xen_memory_setup(void)
> >  {
> > +	static __initdata struct e820entry map[E820MAX];
> > +
> >  	unsigned long max_pfn = xen_start_info->nr_pages;
> > +	struct xen_memory_map memmap;
> > +	unsigned long long mem_end;
> > +	int op;
> > +	int rc;
> > +	int i;
> >  
> >  	max_pfn = min(MAX_DOMAIN_PAGES, max_pfn);
> > +	mem_end = PFN_PHYS((u64)max_pfn);
> > +
> > +	memmap.nr_entries = E820MAX;
> > +	set_xen_guest_handle(memmap.buffer, map);
> > +
> > +	op = xen_initial_domain() ?
> > +		XENMEM_machine_memory_map :
> > +		XENMEM_memory_map;
> > +	rc = HYPERVISOR_memory_op(op, &memmap);
> > +	if (rc == -ENOSYS) {
> > +		memmap.nr_entries = 1;
> > +		map[0].addr = 0ULL;
> > +		map[0].size = mem_end;
> > +		/* 8MB slack (to balance backend allocations). */
> > +		map[0].size += 8ULL << 20;
> > +		map[0].type = E820_RAM;
> > +		rc = 0;
> > +	}
> > +	BUG_ON(rc);
> >  
> >  	e820.nr_map = 0;
> > -
> > -	e820_add_region(0, PFN_PHYS((u64)max_pfn), E820_RAM);
> > -
> > +	for (i = 0; i < memmap.nr_entries; i++) {
> > +		unsigned long long end = map[i].addr + map[i].size;
> > +		if (map[i].type == E820_RAM) {
> > +			if (map[i].addr > mem_end)
> > +				continue;
> 
> Would it make sense to print out a message saying something to the
> effect of: "You need to increase the CONFIG_XEN_MAX_DOMAIN_MEMORY value to
> take advantage of the extra %d gobs of memory!\n", map[i].size
> 
> Or will this be unneccessary with the later changes that Jeremy has
> for the balloon work?
> 

I think it still makes a lot of sense to print that message because
ballooning might be disabled.

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