Re: [PATCH] x86/amd_node: Fix PCI device reference counting in amd_smn_init()

[Yazen Ghannam <yazen.ghannam@amd.com>]

On Mon, Aug 24, 2026 at 10:59:28PM -0500, Serge Hallyn (AMD) wrote:
> On Mon, Aug 24, 2026 at 12:50:03PM -0500, Yazen Ghannam wrote:
> > The local "root" pointer is a temporary variable used during the device
> > search. Therefore, refcount related to the search iterators should be
> > cleaned up after the search is complete.
> > 
> > Use the __free() cleanup macro to ensure the refcount is decremented
> > when the temporary pointer goes out of scope.
> > 
> > Additionally, increment the refcount when caching a root pointer. This
> > ensures the in-use refcount is separate from the temporary search
> > refcounting.
> > 
> > Fixes: 0a4b61d9c2e4 ("x86/amd_node: Fix AMD root device caching")
> > Reported-by: Sashiko <sashiko-bot@kernel.org>
> > Closes: https://sashiko.dev/#/patchset/20260806160159.230453-1-jason.andryuk%40amd.com
> > Assisted-by: Claude-Code:claude-opus-5
> > Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
> > ---
> >  arch/x86/kernel/amd_node.c | 5 ++---
> >  1 file changed, 2 insertions(+), 3 deletions(-)
> > 
> > diff --git a/arch/x86/kernel/amd_node.c b/arch/x86/kernel/amd_node.c
> > index 0be01725a2a4..312adf73313b 100644
> > --- a/arch/x86/kernel/amd_node.c
> > +++ b/arch/x86/kernel/amd_node.c
> > @@ -247,7 +247,7 @@ __setup("amd_smn_debugfs_enable", amd_smn_enable_dfs);
> >  static int __init amd_smn_init(void)
> >  {
> >  	u16 count, num_roots, roots_per_node, node, num_nodes;
> > -	struct pci_dev *root;
> > +	struct pci_dev *root __free(pci_dev_put) = NULL;
> >  
> >  	if (!cpu_feature_enabled(X86_FEATURE_ZEN))
> >  		return 0;
> > @@ -258,7 +258,6 @@ static int __init amd_smn_init(void)
> >  		return 0;
> >  
> >  	num_roots = 0;
> > -	root = NULL;
> >  	while ((root = get_next_root(root))) {
> >  		pci_dbg(root, "Reserving PCI config space\n");
> >  
> 
> Will this leak the ref taken on the last get_next_root(root) in the
> first loop?  You might need a pci_dev_put(root) before the root = NULL
> above the second loop.  Or I could be wrong.
> 

Yes, I think you're right. Good catch.

I'll send another revision with your suggestion.

Thanks,
Yazen