Re: [patch 0/7] x86/pci: Switch to lockless ECAM configuration mode

From: Thomas Gleixner
Date: Wed Jun 21 2017 - 18:28:16 EST


On Mon, 12 Jun 2017, Andi Kleen wrote:
> On Thu, Mar 16, 2017 at 10:50:02PM +0100, Thomas Gleixner wrote:
> > Andi reported that the Intel Uncore performance monitoring suffers from the
> > global pci_lock which protects the generic PCI config space accessors.
> >
> > This lock can be removed on X86 because all architecture specific config
> > space accessors are either serialized by a seperate lock or can be
> > converted to have their own locking. The mmconfig based access (ECAM) does
> > not require serialization at the config read/write level because the access
> > is a simple byte/word/dword read from or write to the memory mapped
> > configuration space. In that case the lock does not provide any more
> > protection than the hardware provides already.
> >
> > The series converts the CE4100 PCI low level accessors to use the x86
> > specific pci_config_lock and implements the switch over to lockless ECAM
> > configureation space accesors when the system is capable.
> What's the status of this patch series? The lock contention
> problem is still there.

Just rechecked. It still applies and boots (patch 6/7) dropped.

If Bjorn has no objections I can route it through tip tomorrow.