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
