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

[Auger Eric]

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

 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?

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
>>>
>>
>>