Re: [Qemu-devel] [PATCH-for-4.2 v2 3/6] s390x/tcg: Flush the TLB of all CPUs on SSKE and RRBE

[David Hildenbrand <david@redhat.com>]

On 14.08.19 12:06, Alex Bennée wrote:
> 
> David Hildenbrand <david@redhat.com> writes:
> 
>> Whenever we modify a storage key, we shuld flush the TLBs of all CPUs,
>> so the MMU fault handling code can properly consider the changed storage
>> key (to e.g., properly set the reference and change bit on the next
>> accesses).
>>
>> These functions are barely used in modern Linux guests, so the performance
>> implications are neglectable for now.
>>
>> This is a preparation for better reference and change bit handling for
>> TCG, which will require more MMU changes.
>>
>> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
>> ---
>>  target/s390x/mem_helper.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/target/s390x/mem_helper.c b/target/s390x/mem_helper.c
>> index 29d9eaa5b7..ed54265e03 100644
>> --- a/target/s390x/mem_helper.c
>> +++ b/target/s390x/mem_helper.c
>> @@ -1815,6 +1815,8 @@ void HELPER(sske)(CPUS390XState *env, uint64_t r1, uint64_t r2)
>>
>>      key = (uint8_t) r1;
>>      skeyclass->set_skeys(ss, addr / TARGET_PAGE_SIZE, 1, &key);
>> +    /* TODO: Flush only entries with this target address */
>> +    tlb_flush_all_cpus_synced(env_cpu(env));
> 
> Doesn't:
> 
>   tlb_flush_page_all_cpus_synced(env_cpu(env), addr & TARGET_PAGE_MASK);
> 
> do what you want here?

I would have to flush all TLB entries that target this physical page,
not the entry of the single virtual page. So that does, unfortunately,
not work.

-- 

Thanks,

David / dhildenb