Subject: Re: [PATCH] powerpc/lpar: Don't crash on H_PROTECT errors

From: Anshuman Khandual <[email-masked]>
Date: Tue, 01 Mar 2016 11:16:00 +0530

On 03/01/2016 10:57 AM, Aneesh Kumar K.V wrote:
> Tyrel Datwyler <[email-masked]> writes:
> 
>> > On 02/29/2016 03:52 AM, Anshuman Khandual wrote:
>>> >> There are certain condition in which H_PROTECT can return error code
>>> >> other than H_NOT_FOUND and H_SUCCESS. One such being an attempt to
>>> >> update an hpte owned by adjunct partition. Return 0 in that case so
>>> >> that user space will retry the access. In adjunct case this mean we
>>> >> will not make much progress in the user space. But atleast we get a
>>> >> chance to kill the task and avoid taking down the entire box.
>>> >> 
>>> >> Signed-off-by: Aneesh Kumar K.V <[email-masked]>
>>> >> Signed-off-by: Anshuman Khandual <[email-masked]>
>>> >> ---
>>> >>  arch/powerpc/platforms/pseries/lpar.c | 2 +-
>>> >>  1 file changed, 1 insertion(+), 1 deletion(-)
>>> >> 
>>> >> diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c
>>> >> index 477290a..31bcdaf 100644
>>> >> --- a/arch/powerpc/platforms/pseries/lpar.c
>>> >> +++ b/arch/powerpc/platforms/pseries/lpar.c
>>> >> @@ -310,7 +310,7 @@ static long pSeries_lpar_hpte_updatepp(unsigned long slot,
>>> >>  
>>> >>  	pr_devel("ok\n");
>>> >>  
>>> >> -	BUG_ON(lpar_rc != H_SUCCESS);
>>> >> +	WARN_RATELIMIT(lpar_rc != H_SUCCESS, "H_PROTECT returned %lu\n", lpar_rc);
>> >
>> > In the event that we don't get H_NOT_FOUND (which is handled earlier in
>> > the function) or H_SUCCESS this patch assumes H_RESOURCE. It fails to
>> > handle H_PARAMETER which is also a valid return from the H_PROTECT
>> > hypercall.
> One of the possible thing we could do is sent SIGBUS to the application
> rather than taking down the system ?

But in case of H_PARAMETER, its the kernel which generated wrong arguments
which was in it's control, hence BUG_ON will not more appropriate for it ?