Re: [PATCH 2/2] x86: HWPOISON: Report correct address granualityfor huge hwpoison faults

[Wu Fengguang]

On Thu, Oct 07, 2010 at 04:57:21AM +0800, Andi Kleen wrote:
> From: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> 
> An earlier patch fixed the hwpoison fault handling to encode the
> huge page size in the fault code of the page fault handler.
> 
> This is needed to report this information in SIGBUS to user space.
> 
> This is a straight forward patch to pass this information
> through to the signal handling in the x86 specific fault.c
> 
> Cc: x86@xxxxxxxxxx
> Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
> Cc: fengguang.wu@xxxxxxxxx
> Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> ---
>  arch/x86/mm/fault.c |   19 +++++++++++++------
>  1 files changed, 13 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index 4c4508e..1d15a27 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -11,6 +11,7 @@
>  #include <linux/kprobes.h>		/* __kprobes, ...		*/
>  #include <linux/mmiotrace.h>		/* kmmio_handler, ...		*/
>  #include <linux/perf_event.h>		/* perf_sw_event		*/
> +#include <linux/hugetlb.h>		/* hstate_index_to_shift	*/
>  
>  #include <asm/traps.h>			/* dotraplinkage, ...		*/
>  #include <asm/pgalloc.h>		/* pgd_*(), ...			*/
> @@ -160,15 +161,20 @@ is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
>  
>  static void
>  force_sig_info_fault(int si_signo, int si_code, unsigned long address,
> -		     struct task_struct *tsk)
> +		     struct task_struct *tsk, int fault)
>  {
> +	unsigned lsb = 0;
>  	siginfo_t info;
>  
>  	info.si_signo	= si_signo;
>  	info.si_errno	= 0;
>  	info.si_code	= si_code;
>  	info.si_addr	= (void __user *)address;
> -	info.si_addr_lsb = si_code == BUS_MCEERR_AR ? PAGE_SHIFT : 0;

Ah you changed the conditional 0..

> +	if (fault & VM_FAULT_HWPOISON_LARGE)
> +		lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); 
> +	if (fault & VM_FAULT_HWPOISON)
> +		lsb = PAGE_SHIFT;
> +	info.si_addr_lsb = lsb;
>  
>  	force_sig_info(si_signo, &info, tsk);
>  }
> @@ -731,7 +737,7 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
>  		tsk->thread.error_code	= error_code | (address >= TASK_SIZE);
>  		tsk->thread.trap_no	= 14;
>  
> -		force_sig_info_fault(SIGSEGV, si_code, address, tsk);
> +		force_sig_info_fault(SIGSEGV, si_code, address, tsk, 0);

..and it's sure reasonable.

Reviewed-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>

Thanks,
Fengguang
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