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From: Bjorn Helgaas <helgaas@kernel.org>
To: Rui Wang <rui.y.wang@intel.com>
Cc: tglx@linutronix.de, rjw@rjwysocki.net, tony.luck@intel.com,
	bhelgaas@google.com, linux-acpi@vger.kernel.org,
	linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH V3 1/3] x86/ioapic: Support hot-removal of IOAPICs present during boot
Date: Wed, 22 Jun 2016 09:53:54 -0500	[thread overview]
Message-ID: <20160622145354.GA25485@localhost> (raw)
In-Reply-To: <1466579612-20417-1-git-send-email-rui.y.wang@intel.com>

On Wed, Jun 22, 2016 at 03:13:32PM +0800, Rui Wang wrote:
> On Friday, June 17, 2016 1:10 AM, Bjorn Helgaas wrote:
> > ioapic_insert_resources() is x86-specific, but I'm not sure why; it seems
> > like it does things that should be applicable to ia64 as well.
> > 
> > acpi_ioapic_add() is not x86-specific, and it is called from
> > acpi_pci_root_add() for the hot-add case.  You're adding an x86-xpecific call
> > in pci_assign_unassigned_resources().  Why should the hot-add case be for
> > all arches, but the boot-time case only for x86?
> 
> Hi Bjorn,
> 
> It turns out that IOAPIC hotplug has not been pursued on ia64. There were
> demos showing CPU sockets online/offline on ia64 but the CPUs had no IIO,
> thus no IOAPIC hotplug.

That doesn't mean we need to write code that's gratuitously x86-specific.

> So to answer the first question:
> ioapic_insert_resources() is x86-specific because it's inserting what has
> been setup in io_apic_init_mappings() which, through mpc_ioapic_addr(), is
> capable of handling both the static case (acpi_parse_ioapic(), etc.) and the
> hotplug case (acpi_ioapic_add()). But on ia64, there's only the static
> case through acpi_parse_iosapic(), no need for the hotplug case yet.

ioapic_insert_resources() inserts IOAPIC resources on x86.  Where are
IOSAPIC resources inserted on ia64?

> To answer the second question:
> acpi_ioapic_add() is in effect x86-specific, because it's an empty function
> when CONFIG_ACPI_HOTPLUG_IOAPIC isn't defined. And CONFIG_ACPI_HOTPLUG_IOAPIC
> depends on CONFIG_X86_IO_APIC (see drivers/acpi/Kconfig). This was introduced
> in c183619b6 (x86/irq, ACPI: Implement ACPI driver to support IOAPIC hotplug).
> That commit shows the dependency.
> 
> I'll send a newer version with comments explaining these.

I'd rather have code that is not x86-specific than comments explaining why
the code is x86-specific.

  reply	other threads:[~2016-06-22 15:10 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-08  6:59 [PATCH V2 0/3] ioapic hot-removal bugs Rui Wang
2016-06-08  6:59 ` [PATCH V2 1/3] x86/ioapic: Support hot-removal of IOAPICs present during boot Rui Wang
2016-06-08  8:05   ` kbuild test robot
2016-06-08  9:32   ` [PATCH V3 " Rui Wang
2016-06-10 12:57     ` Thomas Gleixner
2016-06-10 13:56       ` Rafael J. Wysocki
2016-06-10 16:43     ` Bjorn Helgaas
2016-06-12  6:06       ` Rui Wang
2016-06-16 17:09         ` Bjorn Helgaas
2016-06-22  7:13           ` Rui Wang
2016-06-22 14:53             ` Bjorn Helgaas [this message]
2016-06-24 15:18               ` Rui Wang
2016-06-22  7:40           ` [PATCH V4 " Rui Wang
2016-06-22 15:14             ` Bjorn Helgaas
2016-06-23  5:11               ` 
2016-06-23 17:34                 ` Bjorn Helgaas
2016-06-24 15:30                   ` Rui Wang
2016-06-26  3:44                   ` [PATCH V5 " Rui Wang
2016-08-08 20:22                     ` Bjorn Helgaas
2016-08-09  3:23                       ` Rui Wang
2016-08-09 12:09                         ` Rafael J. Wysocki
2016-06-08  6:59 ` [PATCH V2 2/3] x86/ioapic: Fix wrong pointers in ioapic_setup_resources() Rui Wang
2016-06-10  9:45   ` [tip:x86/urgent] " tip-bot for Rui Wang
2016-06-10 12:01   ` [tip:x86/apic] x86/ioapic: Fix incorrect " tip-bot for Rui Wang
2016-06-10 12:48   ` [tip:x86/urgent] " tip-bot for Rui Wang
2016-06-08  6:59 ` [PATCH V2 3/3] x86/ioapic: Simplify ioapic_setup_resources() Rui Wang
2016-06-10  9:48   ` [tip:x86/apic] " tip-bot for Rui Wang
2016-06-10 12:54   ` tip-bot for Rui Wang

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