Re: Xen on RP4

[Elliott Mitchell <ehem+xen@xxxxxxx>]

On Fri, Oct 23, 2020 at 04:59:30PM -0700, Stefano Stabellini wrote:
> This is what is going on. kernel/dma/swiotlb.c:swiotlb_init gets called
> and tries to allocate a buffer for the swiotlb. It does so by calling
> 
>   memblock_alloc_low(PAGE_ALIGN(bytes), PAGE_SIZE);
> 
> In your case, the allocation must fail, no_iotlb_memory is set, and I
> expect you see this warning among the boot messages:
> 
>   Cannot allocate buffer
> 
> Later during initialization swiotlb-xen comes in
> (drivers/xen/swiotlb-xen.c:xen_swiotlb_init) and given that io_tlb_start
> is != 0 it thinks the memory is ready to use when actually it is not.

Forgot to respond to this portion even though I'd noticed on my first
read.  I haven't ever observed that message.


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