Re: [PATCH v3] powerpc/pseries/svm: Allocate SWIOTLB buffer anywhere in memory

[Michael Ellerman]

Christoph Hellwig <hch@xxxxxx> writes:
> On Tue, Aug 18, 2020 at 07:11:26PM -0300, Thiago Jung Bauermann wrote:
>> POWER secure guests (i.e., guests which use the Protection Execution
>> Facility) need to use SWIOTLB to be able to do I/O with the hypervisor, but
>> they don't need the SWIOTLB memory to be in low addresses since the
>> hypervisor doesn't have any addressing limitation.
>> 
>> This solves a SWIOTLB initialization problem we are seeing in secure guests
>> with 128 GB of RAM: they are configured with 4 GB of crashkernel reserved
>> memory, which leaves no space for SWIOTLB in low addresses.
>> 
>> To do this, we use mostly the same code as swiotlb_init(), but allocate the
>> buffer using memblock_alloc() instead of memblock_alloc_low().
>> 
>> Signed-off-by: Thiago Jung Bauermann <bauerman@xxxxxxxxxxxxx>
>
> Looks fine to me (except for the pointlessly long comment lines, but I've
> been told that's the powerpc way).

They're 80 columns AFAICS?

cheers