From: Andi Kleen <andi@firstfloor.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Bjorn Helgaas <helgaas@kernel.org>,
Andi Kleen <andi@firstfloor.org>, Andi Kleen <ak@linux.intel.com>,
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: Wed, 15 Mar 2017 17:02:48 -0700 [thread overview]
Message-ID: <20170316000247.GD14380@two.firstfloor.org> (raw)
In-Reply-To: <alpine.DEB.2.20.1703150954180.3554@nanos>
> pci_root_ops is what is finally handed in to pci_scan_root_bus() as ops
> argument for any bus segment no matter which type it is.
mmconfig is only initialized after PCI is initialized
(an ordering problem with ACPI). So it would require
updating existing busses with likely interesting race
conditions.
There are also other ordering problems in the PCI layer,
that is one of the reason early and raw PCI accesses even exist.
>
> The locking aspect is interesting as well. The type0/1 functions are having
> their own internal locking. Oh, well.
Right it could set lockless too. The internal locking is still needed
because there are other users too.
> What we really want is to differentiate bus segments. That means a PCIe
> segment takes mmconfig ops and a PCI segment the type0/1 ops. That way we
> can do what you suggested above, i.e. marking the ecam/mmconfig ops as
> lockless.
There's no need to separate PCIe and PCI. mmconfig has nothing to do
with that.
> Sure that's more work than just whacking a sloppy quirk into the code, but
> the right thing to do.
Before proposing grandiose plans it would be better if you
acquired some basic understanding of the constraints this
code is operating under first.
-Andi
next prev parent reply other threads:[~2017-03-16 0:03 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
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 [this message]
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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