Re: [PATCH 1/2] XEN, X86: Improve semantic support for pagetable_reserve PVOP

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Fri, Aug 10, 2012 at 03:17:06PM +0100, Attilio Rao wrote:
> - Allow xen_mapping_pagetable_reserve() to handle a start different from
>   pgt_buf_start, but still bigger than it.
> - Add checks to xen_mapping_pagetable_reserve() and native_pagetable_reserve()
>   for verifying start and end are contained in the range
>   [pgt_buf_start, pgt_buf_top].
> - In xen_mapping_pagetable_reserve(), change printk into pr_debug.
> - In xen_mapping_pagetable_reserve(), print out diagnostic only if there is
>   an actual need to do that (or, in other words, if there are actually some
>   pages going to switch from RO to RW).
> 
> Signed-off-by: Attilio Rao <attilio.rao@citrix.com>
> ---
>  arch/x86/mm/init.c |    4 ++++
>  arch/x86/xen/mmu.c |   22 ++++++++++++++++++++--
>  2 files changed, 24 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
> index e0e6990..c5849b6 100644
> --- a/arch/x86/mm/init.c
> +++ b/arch/x86/mm/init.c
> @@ -92,6 +92,10 @@ static void __init find_early_table_space(struct map_range *mr, unsigned long en
>  
>  void __init native_pagetable_reserve(u64 start, u64 end)
>  {
> +	if (start < PFN_PHYS(pgt_buf_start) || end > PFN_PHYS(pgt_buf_top))
> +		panic("Invalid address range: [%llu - %llu] should be a subset of [%llu - %llu]\n"
> +			start, end, PFN_PHYS(pgt_buf_start),
> +			PFN_PHYS(pgt_buf_top));
>  	memblock_reserve(start, end - start);
>  }
>  
> diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> index b65a761..8d943e0a 100644
> --- a/arch/x86/xen/mmu.c
> +++ b/arch/x86/xen/mmu.c
> @@ -1180,12 +1180,30 @@ static void __init xen_pagetable_setup_start(pgd_t *base)
>  
>  static __init void xen_mapping_pagetable_reserve(u64 start, u64 end)
>  {
> +	u64 sh_start;

sh... shared? shell? Can it be just 'begin' or 'pgt_buf_start_phys' ?
Or 'start_phys' ?
Perhaps 'orig_start' ? 'early_start'? '_start'?

> +
> +	sh_start = PFN_PHYS(pgt_buf_start);
> +
> +	if (start < sh_start || end > PFN_PHYS(pgt_buf_top))
> +		panic("Invalid address range: [%llu - %llu] should be a subset of [%llu - %llu]\n"
> +			start, end, sh_start, PFN_PHYS(pgt_buf_top));
> +
> +	/* set RW the initial range */
> +	if  (start != sh_start)
> +		pr_debug("xen: setting RW the range %llx - %llx\n",
> +			sh_start, start);
> +	while (sh_start < start) {
> +		make_lowmem_page_readwrite(__va(sh_start));
> +		sh_start += PAGE_SIZE;
> +	}
> +
>  	/* reserve the range used */
>  	native_pagetable_reserve(start, end);
>  
>  	/* set as RW the rest */
> -	printk(KERN_DEBUG "xen: setting RW the range %llx - %llx\n", end,
> -			PFN_PHYS(pgt_buf_top));
> +	if (end != PFN_PHYS(pgt_buf_top))
> +		pr_debug("xen: setting RW the range %llx - %llx\n",
> +			end, PFN_PHYS(pgt_buf_top));
>  	while (end < PFN_PHYS(pgt_buf_top)) {
>  		make_lowmem_page_readwrite(__va(end));
>  		end += PAGE_SIZE;
> -- 
> 1.7.2.5