Re: [PATCH v4] target/s390x: Implement the MVPG condition-code-option bit

[David Hildenbrand]

> Am 09.03.2021 um 22:05 schrieb Thomas Huth <thuth@redhat.com>:
> 
> On 04/03/2021 09.10, David Hildenbrand wrote:
>>> On 03.03.21 22:36, Richard Henderson wrote:
>>> On 3/3/21 1:22 PM, David Hildenbrand wrote:
>>>> 
>>>>> Am 03.03.2021 um 22:19 schrieb Richard Henderson 
>>>>> <richard.henderson@linaro.org>:
>>>>> 
>>>>> On 3/3/21 1:11 PM, David Hildenbrand wrote:
>>>>>> MMIO on s390x? :)
>>>>> 
>>>>> hw/s390x/s390-pci-bus.c, memory_region_init_io*().
>>>>> 
>>>> 
>>>> ... part of system address space where a CPU could stumble over it?
>>> 
>>> Impossible to tell within 3 layers of object wrappers.  :-(
>>> I suppose I have no idea how "pci" was hacked onto s390x.
>> You've used the right words to describe "pci" (!) on s390x.
>> IIRC, there is no MMIO: configuration space accesses etc. are performed 
>> using special access instructions - which will "emulate" the MMIO access 
>> performed on other archs via simple read/write instructions.
>> Ordinary instructions (e.g., mvpg) that operate on the system address space 
>> should never stumble over MMIO regions - because that concept does not exist 
>> on s390x.
> 
> Sorry, guys, you've lost me here ... is there now something left to do for 
> this patch or is it good as it is?

I think that check for invalid TLB should be replaced by a check against host 
== NULL.