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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Bjorn Helgaas <bhelgaas@google.com>
Cc: Steven Newbury <steve@snewbury.org.uk>,
	Yinghai Lu <yinghai@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 02/11] PCI: Try to allocate mem64 above 4G at first
Date: Wed, 30 May 2012 09:33:00 -0700	[thread overview]
Message-ID: <CA+55aFzeG4a1gAxTp1G6252xCrxpB=5x_aDkjtU4WY0o0nqC+w@mail.gmail.com> (raw)
In-Reply-To: <CAErSpo6zU898KBv+vFFkymMjpDrPokj0dJq9MMX0z6WZOALbmQ@mail.gmail.com>

On Wed, May 30, 2012 at 9:27 AM, Bjorn Helgaas <bhelgaas@google.com> wrote:
>
> You're right, the spec does allow the upper 16 bits of I/O BARs to be
> hardwired to zero (PCI spec rev 3.0, p. 226), so this part does make
> some sense.  I don't think it applies to x86, since I don't think
> there's a way to generate an I/O access to anything above 64K, but it
> could help other arches.
>
> I'm inclined to be conservative and wait until we find a problem where
> a patch like this would help.

I agree. I would be *very* suspicious of "it might help with other
architectures".

Sure, other architectures might be using non-16-bit IO addresses for
their motherboard resources (just because they can). However, any
hotplug device is most likely (by far) to have been tested and
designed for x86, which means that even if it might look like it has
more than 16 bits of IO space, it will never have been tested that
way.

So rather than make it likely to help other architectures, I'd say
that it would make it likely to break things.

                 Linus

  parent reply	other threads:[~2012-05-30 16:34 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-05-23  6:34 [PATCH 00/11] PCI: resource allocation related Yinghai Lu
2012-05-23  6:34 ` [PATCH 01/11] PCI: Should add children device res to fail list Yinghai Lu
2012-05-23  6:34 ` [PATCH 02/11] PCI: Try to allocate mem64 above 4G at first Yinghai Lu
2012-05-23 15:57   ` Linus Torvalds
2012-05-23 17:30     ` Yinghai Lu
2012-05-23 18:40       ` Yinghai Lu
2012-05-25  4:36         ` Bjorn Helgaas
2012-05-25 17:53           ` Yinghai Lu
2012-05-25 18:39             ` Yinghai Lu
2012-05-25 19:37               ` Bjorn Helgaas
2012-05-25 20:18                 ` H. Peter Anvin
2012-05-25 20:19                 ` Yinghai Lu
2012-05-25 21:55                   ` Bjorn Helgaas
2012-05-25 21:58                     ` H. Peter Anvin
2012-05-25 22:14                       ` Bjorn Helgaas
2012-05-25 23:10                     ` Yinghai Lu
2012-05-26  0:12                       ` Bjorn Helgaas
2012-05-26 15:01                         ` Bjorn Helgaas
2012-05-29 17:56                           ` Yinghai Lu
2012-05-29 17:55                         ` Yinghai Lu
2012-05-29 17:57                           ` H. Peter Anvin
2012-05-29 18:17                             ` Yinghai Lu
2012-05-29 19:03                               ` H. Peter Anvin
2012-05-29 20:46                                 ` Yinghai Lu
2012-05-29 20:50                                   ` H. Peter Anvin
2012-06-01 23:30                                     ` Yinghai Lu
2012-06-04  1:05                                       ` Bjorn Helgaas
2012-06-05  2:37                                         ` Yinghai Lu
2012-06-05  4:50                                           ` Bjorn Helgaas
2012-06-05  5:04                                             ` Yinghai Lu
2012-06-06  9:44                                               ` Steven Newbury
2012-06-06 16:18                                                 ` Bjorn Helgaas
     [not found]                                                   ` <CAGLnvc_ejMWiiubVMo7DLz5ZVn1iMbf67FB4H7crRCCTRRqt2A@mail.gmail.com>
2012-07-04  3:00                                                     ` joeyli
2012-05-29 20:53                                   ` David Miller
2012-05-29 19:23                               ` Bjorn Helgaas
2012-05-29 20:40                                 ` Yinghai Lu
2012-05-29 23:24                                   ` Bjorn Helgaas
2012-05-29 23:27                                   ` Bjorn Helgaas
2012-05-29 23:33                                     ` Yinghai Lu
2012-05-29 23:47                                       ` Bjorn Helgaas
2012-05-30  7:40                                     ` Steven Newbury
2012-05-30 16:27                                       ` Bjorn Helgaas
2012-05-30 16:30                                         ` H. Peter Anvin
2012-05-30 16:33                                         ` Linus Torvalds [this message]
2012-05-23  6:34 ` [PATCH 03/11] intel-gtt: Read 64bit for gmar_bus_addr Yinghai Lu
2012-05-23  7:21   ` Dave Airlie
2012-05-23  7:44     ` Daniel Vetter
2012-05-23  6:34 ` [PATCH 04/11] PCI: Make sure assign same align with large size resource at first Yinghai Lu
2012-05-23  6:34 ` [PATCH 05/11] resources: Split out __allocate_resource() Yinghai Lu
2012-05-23  6:34 ` [PATCH 06/11] resource: make find_resource could return just fit resource Yinghai Lu
2012-05-23  6:34 ` [PATCH 07/11] PCI: Don't allocate small resource in big empty space Yinghai Lu
2012-05-23  6:34 ` [PATCH 08/11] resource: only return range with needed align Yinghai Lu
2012-05-23  6:34 ` [PATCH 09/11] PCI: Add is_pci_iov_resource_idx() Yinghai Lu
2012-05-23  6:34 ` [PATCH 10/11] PCI: Sort unassigned resources with correct alignment Yinghai Lu
2012-05-23  6:34 ` [PATCH 11/11] PCI: Treat ROM resource as optional during assigning Yinghai Lu

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