Re: [PATCH v5 02/10] irqchip/gic-v3-its: Align shared ITS allocations to the CoCo shared granule size

[Marc Zyngier <maz@kernel.org>]

On Mon, 06 Jul 2026 14:42:17 +0100,
Aneesh Kumar K.V <aneesh.kumar@kernel.org> wrote:
> 
> Marc Zyngier <maz@kernel.org> writes:
> 
> > On Mon, 06 Jul 2026 07:04:24 +0100,
> > "Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org> wrote:
> >> 
> >> ITS tables allocated by the coco guest are shared with the hypervisor.
> >> These allocations must satisfy the host shared-buffer granule size so that
> >> the full converted range is safe for host access.
> >> 
> >> Allocate ITS pages using a size rounded up to the shared granule size and
> >> use the same allocation order when encrypting, decrypting and freeing the
> >> memory. Also grow the ITT cache in shared-granule sized chunks instead of
> >> assuming PAGE_SIZE is sufficient.
> >> 
> >> Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
> >> ---
> >>  drivers/irqchip/irq-gic-v3-its.c | 17 +++++++++++------
> >>  1 file changed, 11 insertions(+), 6 deletions(-)
> >> 
> >> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> >> index b57d81ad33a0..5d6d38aa0dae 100644
> >> --- a/drivers/irqchip/irq-gic-v3-its.c
> >> +++ b/drivers/irqchip/irq-gic-v3-its.c
> >> @@ -213,16 +213,17 @@ static gfp_t gfp_flags_quirk;
> >>  static struct page *its_alloc_pages_node(int node, gfp_t gfp,
> >>  					 unsigned int order)
> >>  {
> >> +	unsigned int alloc_order;
> >>  	struct page *page;
> >>  	int ret = 0;
> >>  
> >> -	page = alloc_pages_node(node, gfp | gfp_flags_quirk, order);
> >> -
> >> +	alloc_order = get_order(mem_cc_align_to_shared_granule(PAGE_SIZE << order));
> >> +	page = alloc_pages_node(node, gfp | gfp_flags_quirk, alloc_order);
> >>  	if (!page)
> >>  		return NULL;
> >>  
> >>  	ret = set_memory_decrypted((unsigned long)page_address(page),
> >> -				   1 << order);
> >> +				   1 << alloc_order);
> >>  	/*
> >>  	 * If set_memory_decrypted() fails then we don't know what state the
> >>  	 * page is in, so we can't free it. Instead we leak it.
> >> @@ -241,13 +242,16 @@ static struct page *its_alloc_pages(gfp_t gfp, unsigned int order)
> >>  
> >>  static void its_free_pages(void *addr, unsigned int order)
> >>  {
> >> +	int alloc_order;
> >> +
> >> +	alloc_order = get_order(mem_cc_align_to_shared_granule(PAGE_SIZE << order));
> >>  	/*
> >>  	 * If the memory cannot be encrypted again then we must leak the pages.
> >>  	 * set_memory_encrypted() will already have WARNed.
> >>  	 */
> >> -	if (set_memory_encrypted((unsigned long)addr, 1 << order))
> >> +	if (set_memory_encrypted((unsigned long)addr, 1 << alloc_order))
> >>  		return;
> >> -	free_pages((unsigned long)addr, order);
> >> +	free_pages((unsigned long)addr, alloc_order);
> >
> > The comments I had in [1] are still applicable.
> >
> > 	M.
> >
> > [1] https://lore.kernel.org/all/86zf2ozrb8.wl-maz@kernel.org/
> >
> 
> I renamed it to alloc_order to make it clear that it refers to the
> allocation order rather than the requested order. If you feel strongly
> about not introducing another variable, I'll drop the new variable.

I do. At the very least, to avoid you changing the type of the order
in its_free_pages(). These things do matter.

	M.

-- 
Without deviation from the norm, progress is not possible.