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

From: Andi Kleen <ak@linux.intel.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Bjorn Helgaas <helgaas@kernel.org>,
	x86@kernel.org, Peter Anvin <hpa@zytor.com>,
	Borislav Petkov <bp@alien8.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Stephane Eranian <eranian@google.com>
Subject: Re: [patch 0/7] x86/pci: Switch to lockless ECAM configuration mode
Date: Mon, 12 Jun 2017 17:25:36 -0700	[thread overview]
Message-ID: <20170613002536.GA21242@tassilo.jf.intel.com> (raw)
In-Reply-To: <20170316215002.726697858@linutronix.de>

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.

Thanks,

-Andi