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SubjectRe: [patch V2 34/46] PCI/MSI: Make arch_.*_msi_irq[s] fallbacks selectable
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On Wed, 2020-08-26 at 13:17 +0200, Thomas Gleixner wrote:
> From: Thomas Gleixner <tglx@linutronix.de>
>
> The arch_.*_msi_irq[s] fallbacks are compiled in whether an architecture
> requires them or not. Architectures which are fully utilizing hierarchical
> irq domains should never call into that code.
>
> It's not only architectures which depend on that by implementing one or
> more of the weak functions, there is also a bunch of drivers which relies
> on the weak functions which invoke msi_controller::setup_irq[s] and
> msi_controller::teardown_irq.
>
> Make the architectures and drivers which rely on them select them in Kconfig
> and if not selected replace them by stub functions which emit a warning and
> fail the PCI/MSI interrupt allocation.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Today's linux-next will have some warnings on s390x:

.config: https://gitlab.com/cailca/linux-mm/-/blob/master/s390.config

WARNING: unmet direct dependencies detected for PCI_MSI_ARCH_FALLBACKS
Depends on [n]: PCI [=n]
Selected by [y]:
- S390 [=y]

WARNING: unmet direct dependencies detected for PCI_MSI_ARCH_FALLBACKS
Depends on [n]: PCI [=n]
Selected by [y]:
- S390 [=y]

> ---
> V2: Make the architectures (and drivers) which need the fallbacks select them
> and not the other way round (Bjorn).
> ---
> arch/ia64/Kconfig | 1 +
> arch/mips/Kconfig | 1 +
> arch/powerpc/Kconfig | 1 +
> arch/s390/Kconfig | 1 +
> arch/sparc/Kconfig | 1 +
> arch/x86/Kconfig | 1 +
> drivers/pci/Kconfig | 3 +++
> drivers/pci/controller/Kconfig | 3 +++
> drivers/pci/msi.c | 3 ++-
> include/linux/msi.h | 31 ++++++++++++++++++++++++++-----
> 10 files changed, 40 insertions(+), 6 deletions(-)
>
> --- a/arch/ia64/Kconfig
> +++ b/arch/ia64/Kconfig
> @@ -56,6 +56,7 @@ config IA64
> select NEED_DMA_MAP_STATE
> select NEED_SG_DMA_LENGTH
> select NUMA if !FLATMEM
> + select PCI_MSI_ARCH_FALLBACKS
> default y
> help
> The Itanium Processor Family is Intel's 64-bit successor to
> --- a/arch/mips/Kconfig
> +++ b/arch/mips/Kconfig
> @@ -86,6 +86,7 @@ config MIPS
> select MODULES_USE_ELF_REL if MODULES
> select MODULES_USE_ELF_RELA if MODULES && 64BIT
> select PERF_USE_VMALLOC
> + select PCI_MSI_ARCH_FALLBACKS
> select RTC_LIB
> select SYSCTL_EXCEPTION_TRACE
> select VIRT_TO_BUS
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -246,6 +246,7 @@ config PPC
> select OLD_SIGACTION if PPC32
> select OLD_SIGSUSPEND
> select PCI_DOMAINS if PCI
> + select PCI_MSI_ARCH_FALLBACKS
> select PCI_SYSCALL if PCI
> select PPC_DAWR if PPC64
> select RTC_LIB
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -185,6 +185,7 @@ config S390
> select OLD_SIGSUSPEND3
> select PCI_DOMAINS if PCI
> select PCI_MSI if PCI
> + select PCI_MSI_ARCH_FALLBACKS
> select SPARSE_IRQ
> select SYSCTL_EXCEPTION_TRACE
> select THREAD_INFO_IN_TASK
> --- a/arch/sparc/Kconfig
> +++ b/arch/sparc/Kconfig
> @@ -43,6 +43,7 @@ config SPARC
> select GENERIC_STRNLEN_USER
> select MODULES_USE_ELF_RELA
> select PCI_SYSCALL if PCI
> + select PCI_MSI_ARCH_FALLBACKS
> select ODD_RT_SIGACTION
> select OLD_SIGSUSPEND
> select CPU_NO_EFFICIENT_FFS
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -225,6 +225,7 @@ config X86
> select NEED_SG_DMA_LENGTH
> select PCI_DOMAINS if PCI
> select PCI_LOCKLESS_CONFIG if PCI
> + select PCI_MSI_ARCH_FALLBACKS
> select PERF_EVENTS
> select RTC_LIB
> select RTC_MC146818_LIB
> --- a/drivers/pci/Kconfig
> +++ b/drivers/pci/Kconfig
> @@ -56,6 +56,9 @@ config PCI_MSI_IRQ_DOMAIN
> depends on PCI_MSI
> select GENERIC_MSI_IRQ_DOMAIN
>
> +config PCI_MSI_ARCH_FALLBACKS
> + bool
> +
> config PCI_QUIRKS
> default y
> bool "Enable PCI quirk workarounds" if EXPERT
> --- a/drivers/pci/controller/Kconfig
> +++ b/drivers/pci/controller/Kconfig
> @@ -41,6 +41,7 @@ config PCI_TEGRA
> bool "NVIDIA Tegra PCIe controller"
> depends on ARCH_TEGRA || COMPILE_TEST
> depends on PCI_MSI_IRQ_DOMAIN
> + select PCI_MSI_ARCH_FALLBACKS
> help
> Say Y here if you want support for the PCIe host controller found
> on NVIDIA Tegra SoCs.
> @@ -67,6 +68,7 @@ config PCIE_RCAR_HOST
> bool "Renesas R-Car PCIe host controller"
> depends on ARCH_RENESAS || COMPILE_TEST
> depends on PCI_MSI_IRQ_DOMAIN
> + select PCI_MSI_ARCH_FALLBACKS
> help
> Say Y here if you want PCIe controller support on R-Car SoCs in host
> mode.
> @@ -103,6 +105,7 @@ config PCIE_XILINX_CPM
> bool "Xilinx Versal CPM host bridge support"
> depends on ARCH_ZYNQMP || COMPILE_TEST
> select PCI_HOST_COMMON
> + select PCI_MSI_ARCH_FALLBACKS
> help
> Say 'Y' here if you want kernel support for the
> Xilinx Versal CPM host bridge.
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -58,8 +58,8 @@ static void pci_msi_teardown_msi_irqs(st
> #define pci_msi_teardown_msi_irqs arch_teardown_msi_irqs
> #endif
>
> +#ifdef CONFIG_PCI_MSI_ARCH_FALLBACKS
> /* Arch hooks */
> -
> int __weak arch_setup_msi_irq(struct pci_dev *dev, struct msi_desc *desc)
> {
> struct msi_controller *chip = dev->bus->msi;
> @@ -132,6 +132,7 @@ void __weak arch_teardown_msi_irqs(struc
> {
> return default_teardown_msi_irqs(dev);
> }
> +#endif /* CONFIG_PCI_MSI_ARCH_FALLBACKS */
>
> static void default_restore_msi_irq(struct pci_dev *dev, int irq)
> {
> --- a/include/linux/msi.h
> +++ b/include/linux/msi.h
> @@ -193,17 +193,38 @@ void pci_msi_mask_irq(struct irq_data *d
> void pci_msi_unmask_irq(struct irq_data *data);
>
> /*
> - * The arch hooks to setup up msi irqs. Those functions are
> - * implemented as weak symbols so that they /can/ be overriden by
> - * architecture specific code if needed.
> + * The arch hooks to setup up msi irqs. Default functions are implemented
> + * as weak symbols so that they /can/ be overriden by architecture specific
> + * code if needed. These hooks must be enabled by the architecture or by
> + * drivers which depend on them via msi_controller based MSI handling.
> + *
> + * If CONFIG_PCI_MSI_ARCH_FALLBACKS is not selected they are replaced by
> + * stubs with warnings.
> */
> +#ifdef CONFIG_PCI_MSI_DISABLE_ARCH_FALLBACKS
> int arch_setup_msi_irq(struct pci_dev *dev, struct msi_desc *desc);
> void arch_teardown_msi_irq(unsigned int irq);
> int arch_setup_msi_irqs(struct pci_dev *dev, int nvec, int type);
> void arch_teardown_msi_irqs(struct pci_dev *dev);
> -void arch_restore_msi_irqs(struct pci_dev *dev);
> -
> void default_teardown_msi_irqs(struct pci_dev *dev);
> +#else
> +static inline int arch_setup_msi_irqs(struct pci_dev *dev, int nvec, int
> type)
> +{
> + WARN_ON_ONCE(1);
> + return -ENODEV;
> +}
> +
> +static inline void arch_teardown_msi_irqs(struct pci_dev *dev)
> +{
> + WARN_ON_ONCE(1);
> +}
> +#endif
> +
> +/*
> + * The restore hooks are still available as they are useful even
> + * for fully irq domain based setups. Courtesy to XEN/X86.
> + */
> +void arch_restore_msi_irqs(struct pci_dev *dev);
> void default_restore_msi_irqs(struct pci_dev *dev);
>
> struct msi_controller {
>

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