Re: [PATCH kernel v2] powerpc/mm: Flush radix process translations when setting MMU type

[Laurent Vivier <lvivier@redhat.com>]

On 07/02/2018 18:49, Daniel Henrique Barboza wrote:
> 
> 
> On 02/07/2018 12:33 PM, Laurent Vivier wrote:
>> On 01/02/2018 06:09, Alexey Kardashevskiy wrote:
>>> Radix guests do normally invalidate process-scoped translations when
>>> a new pid is allocated but migrated guests do not invalidate these so
>>> migrated guests crash sometime, especially easy to reproduce with
>>> migration happening within first 10 seconds after the guest boot
>>> start on
>>> the same machine.
>>>
>>> This adds the "Invalidate process-scoped translations" flush to fix
>>> radix guests migration.
>>>
>>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>>> ---
>>> Changes:
>>> v2:
>>> * removed PPC_TLBIE_5() from the !(old&PATH_HR) case as it is pointless
>>> on hash
>>>
>>> ---
>>>
>>>
>>> Not so sure that "process-scoped translations" only require flushing
>>> at pid allocation and migration.
>>>
>>> ---
>>>   arch/powerpc/mm/pgtable_64.c | 2 ++
>>>   1 file changed, 2 insertions(+)
>>>
>>> diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c
>>> index c9a623c..d75dd52 100644
>>> --- a/arch/powerpc/mm/pgtable_64.c
>>> +++ b/arch/powerpc/mm/pgtable_64.c
>>> @@ -471,6 +471,8 @@ void mmu_partition_table_set_entry(unsigned int
>>> lpid, unsigned long dw0,
>>>       if (old & PATB_HR) {
>>>           asm volatile(PPC_TLBIE_5(%0,%1,2,0,1) : :
>>>                    "r" (TLBIEL_INVAL_SET_LPID), "r" (lpid));
>>> +        asm volatile(PPC_TLBIE_5(%0,%1,2,1,1) : :
>>> +                 "r" (TLBIEL_INVAL_SET_LPID), "r" (lpid));
>>>           trace_tlbie(lpid, 0, TLBIEL_INVAL_SET_LPID, lpid, 2, 0, 1);
>>>       } else {
>>>           asm volatile(PPC_TLBIE_5(%0,%1,2,0,0) : :
>>>
>> This patch fixes for me a VM migration crash on POWER9.
> 
> Same here.
> 
> Tested-by: Daniel Henrique Barboza <danielhb@linux.vnet.ibm.com>
> 
>>
>> Tested-by: Laurent Vivier <lvivier@redhat.com>

Any hope to have this patch merged soon?

It fixes a real problem and migration of VM is not reliable without it.

Thanks,
Laurent