Ping: [PATCH] PCI: drop pci_segments_init()

[Jan Beulich <jbeulich@xxxxxxxx>]

On 26.02.2025 12:38, Jan Beulich wrote:
> Have callers invoke pci_add_segment() directly instead: With radix tree
> initialization moved out of the function, its name isn't quite
> describing anymore what it actually does.
> 
> On x86 move the logic into __start_xen() itself, to reduce the risk of
> re-introducing ordering issues like the one which was addressed by
> 26fe09e34566 ("radix-tree: introduce RADIX_TREE{,_INIT}()").
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Arm maintainers: May I ask for an ack (or ...

> ---
> This is entirely optional and up for discussion. There certainly also is
> an argument towards keeping the function. Otoh on Arm there is the still
> open question whether segment 0 really is kind of special there (as it
> is on x86, largely for historical reasons), or whether the code can be
> dropped there altogether.

... otherwise) here please?

Jan

> ---
> v4: Move x86 logic into __start_xen() itself.
> v3: Adjust description to account for and re-base over dropped earlier
>     patch.
> v2: New.
> 
> --- a/xen/arch/arm/pci/pci.c
> +++ b/xen/arch/arm/pci/pci.c
> @@ -88,7 +88,8 @@ static int __init pci_init(void)
>      if ( !pci_passthrough_enabled )
>          return 0;
>  
> -    pci_segments_init();
> +    if ( pci_add_segment(0) )
> +        panic("Could not initialize PCI segment 0\n");
>  
>      if ( acpi_disabled )
>          return dt_pci_init();
> --- a/xen/arch/x86/x86_64/mmconfig-shared.c
> +++ b/xen/arch/x86/x86_64/mmconfig-shared.c
> @@ -402,8 +402,6 @@ void __init acpi_mmcfg_init(void)
>  {
>      bool valid = true;
>  
> -    pci_segments_init();
> -
>      /* MMCONFIG disabled */
>      if ((pci_probe & PCI_PROBE_MMCONF) == 0)
>          return;
> --- a/xen/arch/x86/setup.c
> +++ b/xen/arch/x86/setup.c
> @@ -1898,6 +1898,13 @@ void asmlinkage __init noreturn __start_
>      setup_system_domains();
>  
>      /*
> +     * Ahead of any ACPI table parsing make sure we have control structures
> +     * for PCI segment 0.
> +     */
> +    if ( pci_add_segment(0) )
> +        panic("Could not initialize PCI segment 0\n");
> +
> +    /*
>       * IOMMU-related ACPI table parsing has to happen before APIC probing, 
> for
>       * check_x2apic_preenabled() to be able to observe respective findings, 
> in
>       * particular iommu_intremap having got turned off.
> --- a/xen/drivers/passthrough/pci.c
> +++ b/xen/drivers/passthrough/pci.c
> @@ -127,12 +127,6 @@ static int pci_segments_iterate(
>      return rc;
>  }
>  
> -void __init pci_segments_init(void)
> -{
> -    if ( !alloc_pseg(0) )
> -        panic("Could not initialize PCI segment 0\n");
> -}
> -
>  int __init pci_add_segment(u16 seg)
>  {
>      return alloc_pseg(seg) ? 0 : -ENOMEM;
> --- a/xen/include/xen/pci.h
> +++ b/xen/include/xen/pci.h
> @@ -219,7 +219,6 @@ void setup_hwdom_pci_devices(struct doma
>                               int (*handler)(uint8_t devfn,
>                                              struct pci_dev *pdev));
>  int pci_release_devices(struct domain *d);
> -void pci_segments_init(void);
>  int pci_add_segment(u16 seg);
>  const unsigned long *pci_get_ro_map(u16 seg);
>  int pci_add_device(u16 seg, u8 bus, u8 devfn,