linux-kernel - Re: [PATCH v3 12/12] acpi, numa: reuse acpi_numa_memory_affinity

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Message-ID: <20160127141847.GR24726@rric.localdomain>
Date:	Wed, 27 Jan 2016 15:18:47 +0100
From:	Robert Richter <robert.richter@...iumnetworks.com>
To:	Hanjun Guo <guohanjun@...wei.com>
CC:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Will Deacon <will.deacon@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	<linux-acpi@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>,
	Ganapatrao Kulkarni <gkulkarni@...iumnetworks.com>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Shannon Zhao <shannon.zhao@...aro.org>,
	Steve Capper <steve.capper@...aro.org>,
	Mark Rutland <mark.rutland@....com>,
	Hanjun Guo <hanjun.guo@...aro.org>
Subject: Re: [PATCH v3 12/12] acpi, numa: reuse
 acpi_numa_memory_affinity_init()

On 27.01.16 14:15:06, Hanjun Guo wrote:
> Hi Robert,
> 
> On 2016/1/25 18:26, Robert Richter wrote:
> > On 23.01.16 17:39:27, Hanjun Guo wrote:
> >> From: Hanjun Guo <hanjun.guo@...aro.org>
> >>
> >> After the cleanup for acpi_numa_memory_affinity_init(),
> >> it can be used for architetures both x86 and arm64, since
> >> CONFIG_MEMORY_HOTPLUG is not enabled for arm64, so no
> >> worry about that.
> >>
> >> Signed-off-by: Hanjun Guo <hanjun.guo@...aro.org>
> >> ---
> >>  arch/arm64/kernel/acpi_numa.c | 42 -------------------------------
> >>  arch/x86/mm/srat.c            | 54 ----------------------------------------
> >>  drivers/acpi/numa.c           | 57 +++++++++++++++++++++++++++++++++++++++++++
> >>  3 files changed, 57 insertions(+), 96 deletions(-)
> > This one reverts acpi_numa_memory_affinity_init() to the x86 version.
> > I rather would prefer the arm64 version for the generic code. We could
> > keep the x86 implementation until x86 maintainers agree to remove them
> > and use the generic one (implemented in a separate patch).
> >
> > Doing so we can move acpi_numa_memory_affinity_init() from the
> > beginning to generic code (used for arm64) and have this last patch to
> > remove the x86 version.
> 
> I think the x86 version is the generic one, all the flags (ACPI_SRAT_MEM_HOT_PLUGGABLE and
> etc) are defined in the ACPI spec, x86 just use all the flags because it support such features.
> For ARM64, firmware should be careful and represent the true platform configuration to
> OS, such as on ARM64, we can't set hotpluggable flag as the ARM64 arch don't support
> memory hot-plug yet (also the firmware don't support it too), if firmware do things right,
> it will be not worries for the kernel.

But you are removing all arm64 from your first patches. Why do you
introduce acpi_numa_memory_affinity_init() in the beginning to remove
it in the end again? I esp. like the arm64 version because of its
direct returns. So I still would like to see generic code for arm64
from the beginning. Maybe have a copy of x86 initially and make
modifications for arm64 to it, or move missing code (hotplug, etc.)
from x86 to generic and remove x86 arch code with the last patch.

-Robert