Re: [PATCH v2 12/14] arm64: realm: Support nonsecure ITS emulation shared

Catalin Marinas
2024-05-22T17:05:37Z

On Wed, May 22, 2024 at 04:52:45PM +0100, Steven Price wrote:
> On 15/05/2024 12:01, Catalin Marinas wrote:
> > On Fri, Apr 12, 2024 at 09:42:11AM +0100, Steven Price wrote:
> >> @@ -3432,7 +3468,16 @@ static struct its_device *its_create_device(struct its_node *its, u32 dev_id,
> >> nr_ites = max(2, nvecs);
> >> sz = nr_ites * (FIELD_GET(GITS_TYPER_ITT_ENTRY_SIZE, its->typer) + 1);
> >> sz = max(sz, ITS_ITT_ALIGN) + ITS_ITT_ALIGN - 1;
> >> - itt = kzalloc_node(sz, GFP_KERNEL, its->numa_node);
> >> + itt_order = get_order(sz);
> >> + page = its_alloc_shared_pages_node(its->numa_node,
> >> + GFP_KERNEL | __GFP_ZERO,
> >> + itt_order);
> >
> > How much do we waste by going for a full page always if this is going to
> > be used on the host?
>
> sz is a minimum of ITS_ITT_ALIGN*2-1 - which is 511 bytes. So
> potentially PAGE_SIZE-512 bytes could be wasted here (minus kmalloc
> overhead).

That I figured out as well but how many times is this path called with a
size smaller than a page?

--
Catalin