On Tue, 27 Jun 2017, Bjorn Helgaas wrote: > On Thu, Mar 16, 2017 at 10:50:06PM +0100, Thomas Gleixner wrote: > > Provide a kernel config option which can be selected by an architecture > > when the low level PCI configuration space accessors in the architecture > > use their own serialization or can operate completely lockless. > > The arch/x86/pci/common.c comment: > > /* > * This interrupt-safe spinlock protects all accesses to PCI > * configuration space. > */ > DEFINE_RAW_SPINLOCK(pci_config_lock); > > is no longer quite correct. Yes. I updated it to: * This interrupt-safe spinlock protects all accesses to PCI configuration * space, except for the mmconfig (ECAM) based operations. > I think the raw_pci_read() and raw_pci_write() implementations are > such that we use the old locked accessors for the first 256 bytes, > even when ECAM is available. Not necessarily a problem, just an > observation. No, we actually don't after the next patch, which replaces the pci_root_ops.read/write function pointers with the lockless ECAM accessors after the end of the initialization, if none of the special quirks replaced raw_pci_ext_ops and mmconfig/ECAM is available. > I guess the uncore PMU registers are in the extended config space. Yes. Thanks, tglx
