Re: [PATCH v3 for-4.20 2/4] radix-tree: introduce RADIX_TREE{,_INIT}()

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 04/02/2025 1:03 pm, Jan Beulich wrote:
> ... now that static initialization is possible. Use RADIX_TREE() for
> pci_segments and ivrs_maps.
>
> This then fixes an ordering issue on x86: With the call to
> radix_tree_init(), acpi_mmcfg_init()'s invocation of pci_segments_init()
> will zap the possible earlier introduction of segment 0 by
> amd_iommu_detect_one_acpi()'s call to pci_ro_device(), and thus the
> write-protection of the PCI devices representing AMD IOMMUs.
>
> Fixes: 3950f2485bbc ("x86/x2APIC: defer probe until after IOMMU ACPI table 
> parsing")
> Requested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> Sadly gcc below 5.x doesn't support compound literals in static
> initializers (Clang 3.5 does). Hence the request in response to v2 has
> to remain un-addressed.
> ---
> v3: Extend description and add Fixes: tag.
> v2: New.
>
> --- a/xen/drivers/passthrough/amd/iommu_init.c
> +++ b/xen/drivers/passthrough/amd/iommu_init.c
> @@ -31,7 +31,7 @@ static struct tasklet amd_iommu_irq_task
>  unsigned int __read_mostly amd_iommu_acpi_info;
>  unsigned int __read_mostly ivrs_bdf_entries;
>  u8 __read_mostly ivhd_type;
> -static struct radix_tree_root ivrs_maps;
> +static RADIX_TREE(ivrs_maps);
>  LIST_HEAD_RO_AFTER_INIT(amd_iommu_head);
>  bool iommuv2_enabled;
>  
> @@ -1408,7 +1408,6 @@ int __init amd_iommu_prepare(bool xt)
>          goto error_out;
>      ivrs_bdf_entries = rc;
>  
> -    radix_tree_init(&ivrs_maps);
>      for_each_amd_iommu ( iommu )
>      {
>          rc = amd_iommu_prepare_one(iommu);
> --- a/xen/drivers/passthrough/pci.c
> +++ b/xen/drivers/passthrough/pci.c
> @@ -68,7 +68,7 @@ bool pcidevs_locked(void)
>      return rspin_is_locked(&_pcidevs_lock);
>  }
>  
> -static struct radix_tree_root pci_segments;
> +static RADIX_TREE(pci_segments);
>  
>  static inline struct pci_seg *get_pseg(u16 seg)
>  {
> @@ -124,7 +124,6 @@ static int pci_segments_iterate(
>  
>  void __init pci_segments_init(void)
>  {
> -    radix_tree_init(&pci_segments);
>      if ( !alloc_pseg(0) )
>          panic("Could not initialize PCI segment 0\n");
>  }
> --- a/xen/include/xen/radix-tree.h
> +++ b/xen/include/xen/radix-tree.h
> @@ -72,6 +72,9 @@ struct radix_tree_root {
>   *** radix-tree API starts here **
>   */
>  
> +#define RADIX_TREE_INIT() {}
> +#define RADIX_TREE(name) struct radix_tree_root name = RADIX_TREE_INIT()

We can still use this form in radix_tree_init(), can't we?

~Andrew