Re: Infinite loop on boot in free_early_partial due to start==end on tip/master

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

> Subject: x86: do not free zero sized per cpu areas
> 
> This avoids an infinite loop in free_early_partial().

The patch fixed PV guests booting on Xen. I've added my
Tested-by .. Please merge it in the release.

Thanks!
> 
> Add a warning to free_early_partial to catch future problems.
> 
> Signed-off-by: Ian Campbell <ian.campbell@citrix.com>

Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> 
> 
> 
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> 
> diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
> index ef6370b..89a3205 100644
> --- a/arch/x86/kernel/setup_percpu.c
> +++ b/arch/x86/kernel/setup_percpu.c
> @@ -140,7 +140,8 @@ static void __init pcpu_fc_free(void *ptr, size_t size)
>  #ifdef CONFIG_NO_BOOTMEM
>  	u64 start = __pa(ptr);
>  	u64 end = start + size;
> -	free_early_partial(start, end);
> +	if (start < end)
> +		free_early_partial(start, end);
>  #else
>  	free_bootmem(__pa(ptr), size);
>  #endif
> diff --git a/kernel/early_res.c b/kernel/early_res.c
> index 3cb2c66..fbde443 100644
> --- a/kernel/early_res.c
> +++ b/kernel/early_res.c
> @@ -333,6 +333,8 @@ void __init free_early_partial(u64 start, u64 end)
>  	struct early_res *r;
>  	int i;
>  
> +	WARN_ON(start>=end);
> +
>  try_next:
>  	i = find_overlapped_early(start, end);
>  	if (i >= max_early_res)