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

[Andrew Jones]

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?

> > 
> > 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? kvm-unit-tests, at least arm/arm64, does prepare
an identity map of all physical memory, which explains why the above
is working. 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.

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
> > 
> 
>