Re: [PATCH 0/5] Small PCI refactoring

[Teddy Astie <teddy.astie@xxxxxxxxxx>]

Le 18/05/2026 à 17:22, Teddy Astie a écrit :
> The goal of this series is to make some refactoring of some
> pci primitives to improve codegen and make code less verbose.
>
> A big chunk of it is converting many places where (seg, bus, dev, fn)
> is split into multiples variables and convert it into being just
> pci_sbdf_t, in particular in some PCI function parameters to reduce
> parameter count which usually translate into less registers to pass
> to the function. Moreover, we also avoid translating back and forth
> between pci_sbdf_t and individual (seg, bus, dev, fn).
>
> Latest patch attempts to improve codegen of pci_conf_{read,write}N()
> by making them inline specialized variants of pci_mmcfg_{read,write}()
> in order to eliminate a particular `switch (len)` at compile time.
>
> No intended functional change, aside some parts of the codebase that will
> now correctly handle PCI segment when parsed while it was previously
> ignored (e.g dbgp).
>
> Bloat-o-meter is pretty telling
>
> add/remove: 4/2 grow/shrink: 11/14 up/down: 529/-1470 (-941)
> Function                                     old     new   delta
> pci_mmcfg_base                                 -     106    +106
> parse_pci_sbdf_seg                             -      88     +88
> parse_pci_sbdf                                 -      85     +85
> pci_dev_base                                   -      56     +56
> pci_conf_read16                               92     118     +26
> pci_conf_read8                                92     117     +25
> ehci_dbgp_init                               629     652     +23
> pci_conf_read32                               94     116     +22
> pci_conf_write32                              88     109     +21
> symbols_names                             106435  106452     +17
> symbols_sorted_offsets                     59672   59688     +16
> pci_conf_write16                              94     109     +15
> pci_conf_write8                               94     108     +14
> reserve_unity_map_for_device                 434     445     +11
> symbols_offsets                            31920   31924      +4
> mmcfg_intercept_write                        194     193      -1
> add_one_user_rmrr                            653     644      -9
> __find_dbgp                                   87      60     -27
> pci_device_detect                             89      55     -34
> pci_mmcfg_write                              197     152     -45
> _scan_pci_devices                            286     241     -45
> parse_ivrs_ioapic                            292     235     -57
> parse_rmrr_param                             484     420     -64
> register_one_rmrr                            389     324     -65
> parse_ivrs_hpet                              249     184     -65
> parse_ivmd_param                             651     570     -81
> acpi_parse_dmar                             2625    2520    -105
> get_virt                                     106       -    -106
> pci_mmcfg_read                               189       -    -189
> ns16550_init                                3205    3002    -203
> acpi_parse_dev_scope                        1465    1091    -374
>
> Teddy Astie (5):
>    pci: Introduce parse_pci_sbdf{_seg}()
>    vtd: Use pci_sbdf_t in acpi_parse_dev_scope()
>    pci: Use pci_sbdf_t in pci_device_detect()
>    pci: Parse into pci_sbdf_t directly
>    RFC: pci: Migrate pci_mmcfg_{read,write}() to pci.c
>
>   xen/arch/x86/pv/ro-page-fault.c          |   3 +-
>   xen/arch/x86/x86_64/mmconfig.h           |  43 --------
>   xen/arch/x86/x86_64/mmconfig_64.c        | 106 ++++----------------
>   xen/arch/x86/x86_64/pci.c                | 122 +++++++++++++++++++++--
>   xen/drivers/char/ehci-dbgp.c             |  35 +++----
>   xen/drivers/char/ns16550.c               |  24 ++---
>   xen/drivers/char/xhci-dbc.c              |   6 +-
>   xen/drivers/passthrough/amd/iommu_acpi.c |  26 ++---
>   xen/drivers/passthrough/pci.c            |  16 +--
>   xen/drivers/passthrough/vtd/dmar.c       |  80 ++++++---------
>   xen/drivers/pci/pci.c                    |  18 ++++
>   xen/include/xen/pci.h                    |  11 +-
>   12 files changed, 243 insertions(+), 247 deletions(-)
There are some issues with our mail provider for the cover letter and 
some whitespace issues in one of the patch, will resend tomorrow 
(hopefully correctly this time).
Teddy

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