From: Bjorn Helgaas <helgaas@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Andi Kleen <ak@linux.intel.com>, Andi Kleen <andi@firstfloor.org>,
bhelgaas@google.com, x86@kernel.org, linux-pci@vger.kernel.org,
eranian@google.com, Peter Zijlstra <peterz@infradead.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/4] x86, pci: Add interface to force mmconfig
Date: Tue, 14 Mar 2017 14:47:20 -0500 [thread overview]
Message-ID: <20170314194720.GD26264@bhelgaas-glaptop.roam.corp.google.com> (raw)
In-Reply-To: <alpine.DEB.2.20.1703141849170.3619@nanos>
On Tue, Mar 14, 2017 at 06:56:26PM +0100, Thomas Gleixner wrote:
> On Tue, 14 Mar 2017, Andi Kleen wrote:
> > The other option is to simply make it unconditional. That would
> > be even simpler, but it is a bit more risky. Hmm, I suppose may
> > be worth trying to find out what Windows uses. If they get away
> > with MMCONFIG everywhere we should be too.
>
> From the PCIe spec:
>
> The PCI 3.0 compatible Configuration Space can be accessed using either
> the mechanism defined in the PCI Local Bus Specification or the PCI
> Express Enhanced Configuration Access Mechanism (ECAM) described later in
> this section. Accesses made using either access mechanism are
> equivalent. The PCI Express Extended Configuration Space can only be
> accessed by using the ECAM.
>
> The 1.0 spec has a similar wording (s/3.0/2.3).
>
> Definitely the best way to go.
I agree that it should be fairly safe to do ECAM/MMCONFIG without
locking. Can we handle the decision part by adding a "lockless" bit
to struct pci_ops? Old ops don't mention that bit, so it will be
initialized to zero and we'll do locking as today. ECAM/MMCONFIG ops
can set it and we can skip the locking.
Bjorn
next prev parent reply other threads:[~2017-03-14 19:47 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-02 23:21 [PATCH 1/4] pci: Allow lockless access path to PCI mmconfig Andi Kleen
2017-03-02 23:21 ` [PATCH 2/4] pci: Add generic pci_bus_force_mmconfig interface Andi Kleen
2017-03-14 17:34 ` H. Peter Anvin
2017-03-02 23:21 ` [PATCH 3/4] x86, pci: Add interface to force mmconfig Andi Kleen
2017-03-14 13:55 ` Thomas Gleixner
2017-03-14 15:41 ` Andi Kleen
2017-03-14 16:40 ` Thomas Gleixner
2017-03-14 17:02 ` Andi Kleen
2017-03-14 17:56 ` Thomas Gleixner
2017-03-14 19:47 ` Bjorn Helgaas [this message]
2017-03-15 2:24 ` Andi Kleen
2017-03-15 2:55 ` Bjorn Helgaas
2017-03-15 10:00 ` Thomas Gleixner
2017-03-15 14:09 ` Bjorn Helgaas
2017-03-16 0:02 ` Andi Kleen
2017-03-16 22:45 ` Thomas Gleixner
2017-03-02 23:21 ` [PATCH 4/4] perf/x86/intel/uncore: Enable forced mmconfig for Intel uncore Andi Kleen
2017-03-14 13:06 ` [PATCH 1/4] pci: Allow lockless access path to PCI mmconfig Thomas Gleixner
2017-03-14 17:28 ` H. Peter Anvin
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