Subject: Re: linux-next: Tree for May 3

From: Mike Rapoport <[email-masked]>
Date: Wed, 11 May 2022 17:08:52 +0300

On Wed, May 11, 2022 at 02:37:24PM +0200, Christoph Hellwig wrote:
> On Wed, May 11, 2022 at 10:10:40AM +0000, [email-masked] wrote:
> > Without even trying the patch, I double checked the boot log from
> > 3f70356edf56 and I get a "software IO TLB: Cannot allocate buffer"
> > With the patch its a "software IO TLB: swiotlb_init_remap: failed
> > to allocate tlb structure". So spot on & I feel like an idiot for
> > not spotting that before!
> > 
> > Is failing being fatal valid, or should it fail gracefully like it
> > used to do? To me, blissfully unaware about swiotlb, the "current"
> > behaviour of failing gracefully makes more sense.
> 
> Given that we're at -rc6 I think the most important thing for now is to
> avoid a regression and restore the old behavior.  I'll send out a
> series with this and the nslab related fixes for Xen today.
> 
> But we should look into why allocating the memory fails for your
> plaforms.  Does it have very little memory?  I can't really think
> of why else the memblock allocation for swiotlb would fail.

I guess the default to use memblock_alloc_low() backfires on system with
physical memory living at 0x1000200000:

[    0.000000] Early memory node ranges
[    0.000000]   node   0: [mem 0x0000001000200000-0x000000103fffffff]

The default limit for "low" memory is 0xffffffff and there is simply no
memory there.

-- 
Sincerely yours,
Mike.