Re: [PATCH 02/12] kho: store incoming radix tree in kho_in

[Mike Rapoport <rppt@kernel.org>]

On Mon, May 11, 2026 at 06:28:21PM +0200, Pratyush Yadav wrote:
> On Mon, May 11 2026, Mike Rapoport wrote:
> 
> > On Wed, Apr 29, 2026 at 03:39:04PM +0200, Pratyush Yadav wrote:
> >> From: "Pratyush Yadav (Google)" <pratyush@kernel.org>
> >> 
> >> This allows other functions to also use the radix tree. While at it,
> >> also use kho_get_mem_map_phys() instead of duplicating the code to get
> >> the radix tree root from the FDT.
> >> 
> >> Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
> >> ---
> >>  kernel/liveupdate/kexec_handover.c | 27 ++++++++-------------------
> >>  1 file changed, 8 insertions(+), 19 deletions(-)
> >> 
> >> diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
> >> index ba568d34c5b4..5758dc6fab5d 100644
> >> --- a/kernel/liveupdate/kexec_handover.c
> >> +++ b/kernel/liveupdate/kexec_handover.c
> >> @@ -1294,6 +1294,7 @@ struct kho_in {
> >>  	char previous_release[__NEW_UTS_LEN + 1];
> >>  	u32 kexec_count;
> >>  	struct kho_debugfs dbg;
> >> +	struct kho_radix_tree radix_tree;
> >>  };
> >>  
> >>  static struct kho_in kho_in = {
> >> @@ -1373,24 +1374,10 @@ EXPORT_SYMBOL_GPL(kho_retrieve_subtree);
> >>  
> >>  static int __init kho_mem_retrieve(const void *fdt)
> >>  {
> >> -	struct kho_radix_tree tree;
> >> -	const phys_addr_t *mem;
> >> -	int len;
> >> -
> >> -	/* Retrieve the KHO radix tree from passed-in FDT. */
> >> -	mem = fdt_getprop(fdt, 0, KHO_FDT_MEMORY_MAP_PROP_NAME, &len);
> >> -
> >> -	if (!mem || len != sizeof(*mem)) {
> >> -		pr_err("failed to get preserved KHO memory tree\n");
> >> -		return -ENOENT;
> >> -	}
> >> -
> >> -	if (!*mem)
> >> -		return -EINVAL;
> >> -
> >> -	tree.root = phys_to_virt(*mem);
> >> -	mutex_init(&tree.lock);
> >> -	return kho_radix_walk_tree(&tree, kho_preserved_memory_reserve);
> >> +	kho_in.radix_tree.root = phys_to_virt(kho_get_mem_map_phys(fdt));
> >
> > Do we really want to remove an explicit check for 0 and get a WARN() in
> > kho_radix_walk_tree()?
> 
> If mem_map_phys is 0 then kho_populate() never sets kho_in.scratch_phys
> and thus kho_mem_retrieve() never gets called. So here it will never be
> 0, and if it is, a WARN() is certainly warranted.
> 
> Perhaps I should add a comment since this isn't so obvious?

Yes, please.
After a few weeks it will be completely obscure.
 
> >
> >> +	mutex_init(&kho_in.radix_tree.lock);
> >> +	return kho_radix_walk_tree(&kho_in.radix_tree,
> >> +				   kho_preserved_memory_reserve);
> >>  }
> >>  
> >>  static __init int kho_out_fdt_setup(void)
> >> @@ -1597,8 +1584,10 @@ void __init kho_memory_init(void)
> >>  	if (kho_in.scratch_phys) {
> >>  		kho_scratch = phys_to_virt(kho_in.scratch_phys);
> >>  
> >> -		if (kho_mem_retrieve(kho_get_fdt()))
> >> +		if (kho_mem_retrieve(kho_get_fdt())) {
> >>  			kho_in.fdt_phys = 0;
> >> +			kho_in.radix_tree.root = NULL;
> >
> > I'd make kho_mem_retrieve() void and put these there.
> 
> Sure, will do.
> 
> >
> >> +		}
> >>  	} else {
> >>  		kho_reserve_scratch();
> >>  	}
> >> -- 
> >> 2.54.0.545.g6539524ca2-goog
> >> 
> 
> -- 
> Regards,
> Pratyush Yadav

-- 
Sincerely yours,
Mike.