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

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Date:	Mon, 18 Oct 2010 11:54:12 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Stefano Stabellini <Stefano.Stabellini@...citrix.com>
Cc:	linux-kernel@...r.kernel.org, xen-devel@...ts.xensource.com,
	Jeremy.Fitzhardinge@...rix.com,
	Ian Campbell <ian.campbell@...rix.com>
Subject: Re: [PATCH v3 08/10] xen: use host E820 map for dom0

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?

> +			if (end > mem_end) {
> +				/* Truncate region to max_mem. */
> +				map[i].size -= end - mem_end;
> +			}
> +		}
> +		if (map[i].size > 0)
> +			e820_add_region(map[i].addr, map[i].size, map[i].type);
> +	}
> +	
>  	/*
>  	 * Even though this is normal, usable memory under Xen, reserve
>  	 * ISA memory anyway because too many things think they can poke
> diff --git a/include/xen/interface/memory.h b/include/xen/interface/memory.h
> index d3938d3..4c4b817 100644
> --- a/include/xen/interface/memory.h
> +++ b/include/xen/interface/memory.h
> @@ -186,6 +186,34 @@ struct xen_translate_gpfn_list {
>  };
>  DEFINE_GUEST_HANDLE_STRUCT(xen_translate_gpfn_list);
>  
> +/*
> + * Returns the pseudo-physical memory map as it was when the domain
> + * was started (specified by XENMEM_set_memory_map).
> + * arg == addr of struct xen_memory_map.
> + */
> +#define XENMEM_memory_map           9
> +struct xen_memory_map {
> +    /*
> +     * On call the number of entries which can be stored in buffer. On
> +     * return the number of entries which have been stored in
> +     * buffer.
> +     */
> +    unsigned int nr_entries;
> +
> +    /*
> +     * Entries in the buffer are in the same format as returned by the
> +     * BIOS INT 0x15 EAX=0xE820 call.
> +     */
> +    GUEST_HANDLE(void) buffer;
> +};
> +DEFINE_GUEST_HANDLE_STRUCT(xen_memory_map);
> +
> +/*
> + * Returns the real physical memory map. Passes the same structure as
> + * XENMEM_memory_map.
> + * arg == addr of struct xen_memory_map.
> + */
> +#define XENMEM_machine_memory_map   10
>  
>  /*
>   * Prevent the balloon driver from changing the memory reservation
> -- 
> 1.5.6.5
--
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