Re: [PATCH V2 1/2] Swiotlb: Add swiotlb_alloc_from_low_pages switch

[Tianyu Lan]

On 2/14/2022 9:58 PM, Christoph Hellwig wrote:
> On Mon, Feb 14, 2022 at 07:28:40PM +0800, Tianyu Lan wrote:
> > On 2/14/2022 4:19 PM, Christoph Hellwig wrote:
> > > Adding a function to set the flag doesn't really change much.  As Robin
> > > pointed out last time you should fine a way to just call
> > > swiotlb_init_with_tbl directly with the memory allocated the way you
> > > like it.  Or given that we have quite a few of these trusted hypervisor
> > > schemes maybe add an argument to swiotlb_init that specifies how to
> > > allocate the memory.
> >
> > Thanks for your suggestion. I will try the first approach first approach.
>
> Take a look at the SWIOTLB_ANY flag in this WIP branch:
>
>     http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/swiotlb-init-cleanup
>
> That being said I'm not sure that either this flag or the existing powerpc
> code iѕ actually the right thing to do.  We still need the 4G limited
> buffer to support devices with addressing limitations.  So I think we need
> an additional io_tlb_mem instance for the devices without addressing
> limitations instead.

Hi Christoph:
     Thanks for your patches. I tested these patches in Hyper-V trusted 
VM and system can't boot up. I am debugging and will report back.