Re: [kvm-unit-tests PATCH v7 06/13] arm/arm64: ITS: Introspection tests

[Auger Eric]

Hi Drew,

On 3/30/20 12:19 PM, Andrew Jones wrote:
> On Mon, Mar 30, 2020 at 11:56:00AM +0200, Auger Eric wrote:
>> Hi,
>>
>> On 3/30/20 11:11 AM, Andrew Jones wrote:
>>> On Mon, Mar 30, 2020 at 10:46:57AM +0200, Auger Eric wrote:
>>>> Hi Zenghui,
>>>>
>>>> On 3/30/20 10:30 AM, Zenghui Yu wrote:
>>>>> Hi Eric,
>>>>>
>>>>> On 2020/3/20 17:24, Eric Auger wrote:
>>>>>> +static void its_cmd_queue_init(void)
>>>>>> +{
>>>>>> +    unsigned long order = get_order(SZ_64K >> PAGE_SHIFT);
>>>>>> +    u64 cbaser;
>>>>>> +
>>>>>> +    its_data.cmd_base = (void *)virt_to_phys(alloc_pages(order));
>>>>>
>>>>> Shouldn't the cmd_base (and the cmd_write) be set as a GVA?
>>>> yes it should
>>>
>>> If it's supposed to be a virtual address, when why do the virt_to_phys?
>> What is programmed in CBASER register is a physical address. So the
>> virt_to_phys() is relevant. The inconsistency is in its_allocate_entry()
>> introduced later on where I return the physical address instead of the
>> virtual address. I will fix that.
>>
>>
>>>
>>>>>
>>>>> Otherwise I think we will end-up with memory corruption when writing
>>>>> the command queue.  But it seems that everything just works fine ...
>>>>> So I'm really confused here :-/
>>>> I was told by Paolo that the VA/PA memory map is flat in kvmunit test.
>>>
>>> What does flat mean?
>>
>> Yes I meant an identity map.
>>
>>  kvm-unit-tests, at least arm/arm64, does prepare
>>> an identity map of all physical memory, which explains why the above
>>> is working.
>>
>> should be the same on x86
> 
> Maybe, but I didn't write or review how x86 does their default map, so I
> don't know.
> 
>>
>>  It's doing virt_to_phys(some-virt-addr), which gets a
>>> phys addr, but when the ITS uses it as a virt addr it works because
>>> we *also* have a virt addr == phys addr mapping in the default page
>>> table, which is named "idmap" for good reason.
>>>
>>> I think it would be better to test with the non-identity mapped addresses
>>> though.
>>
>> is there any way to exercise a non idmap?
> 
> You could create your own map and then switch to it. See lib/arm/asm/mmu-api.h
> 
> But, you don't have to switch the whole map to use non-identity mapped
> addresses. Just create new virt mappings to the phys addresses you're
> interested in, and then use those new virt addresses instead. If you're
> worried that somewhere an identity mapped virt address is getting used
> because of a phys/virt address mix up, then you could probably sprinkle
> some assert(virt_to_phys(addr) != addr)'s around to ensure it.

OK. Well I don't know if it is worth the candle. I will review the code
again and fix the remaining inconsistencies I can see.

Thanks

Eric
> 
> Thanks,
> drew
> 
>>
>> Thanks
>>
>> Eric
>>>
>>> Thanks,
>>> drew
>>>
>>>>
>>>>>
>>>>>> +
>>>>>> +    cbaser = ((u64)its_data.cmd_base | (SZ_64K / SZ_4K - 1)    |
>>>>>> GITS_CBASER_VALID);
>>>>>> +
>>>>>> +    writeq(cbaser, its_data.base + GITS_CBASER);
>>>>>> +
>>>>>> +    its_data.cmd_write = its_data.cmd_base;
>>>>>> +    writeq(0, its_data.base + GITS_CWRITER);
>>>>>> +}
>>>>>
>>>>> Otherwise this looks good,
>>>>> Reviewed-by: Zenghui Yu <address@hidden>
>>>> Thanks!
>>>>
>>>> Eric
>>>>>
>>>>>
>>>>> Thanks
>>>>>
>>>>
>>>>
>>
>>