linux-kernel - Re: [PATCH v6 13/14] arm64, acpi, numa: NUMA support based on SRAT and SLIT

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Message-ID: <5734EA38.2040206@caviumnetworks.com>
Date:	Thu, 12 May 2016 13:40:24 -0700
From:	David Daney <ddaney@...iumnetworks.com>
To:	Catalin Marinas <catalin.marinas@....com>
CC:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Will Deacon <will.deacon@....com>,
	Mark Rutland <mark.rutland@....com>,
	<linux-ia64@...r.kernel.org>, David Daney <david.daney@...ium.com>,
	Robert Moore <robert.moore@...el.com>,
	Lv Zheng <lv.zheng@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Frank Rowand <frowand.list@...il.com>, <x86@...nel.org>,
	<linux-acpi@...r.kernel.org>, Ingo Molnar <mingo@...hat.com>,
	Grant Likely <grant.likely@...aro.org>,
	Len Brown <lenb@...nel.org>, Fenghua Yu <fenghua.yu@...el.com>,
	Marc Zyngier <Marc.Zyngier@....com>,
	Jon Masters <jcm@...hat.com>,
	Robert Richter <rrichter@...ium.com>,
	Rob Herring <robh+dt@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	<linux-arm-kernel@...ts.infradead.org>, <devel@...ica.org>,
	Tony Luck <tony.luck@...el.com>,
	<linux-kernel@...r.kernel.org>, Hanjun Guo <hanjun.guo@...aro.org>,
	Ganapatrao Kulkarni <gkulkarni@...iumnetworks.com>
Subject: Re: [PATCH v6 13/14] arm64, acpi, numa: NUMA support based on SRAT
 and SLIT

On 05/12/2016 09:24 AM, Catalin Marinas wrote:
> On Thu, May 12, 2016 at 08:27:08AM -0700, David Daney wrote:
>> On 05/12/2016 02:49 AM, Catalin Marinas wrote:
>>> On Wed, May 11, 2016 at 05:06:13PM -0700, David Daney wrote:
>>>> On 05/11/2016 03:39 AM, Catalin Marinas wrote:
>> [...]
>>>>>
>>>>> I wonder whether you could replace the get_mpidr_in_madt() function with
>>>>> something like acpi_get_phys_id(). It looks like get_mpidr_in_madt()
>>>>> duplicates functionality already available elsewhere.
>>>>
>>>> I just tried that, and it doesn't work.
>>>>
>>>> The problem is that this code is being run very early in the boot, and
>>>> kmalloc cannot be used.  acpi_get_phys_id() and its ilk can only be used
>>>> once we have working kmalloc.  We need to extract the NUMA information early
>>>> like this precisely because it is needed to initializing the slab system
>>>>
>>>> Notice that we are using early_acpi_os_unmap_memory() et al. in
>>>> get_mpidr_in_madt() explicitly for this reason.
>>>>
>>>> In summary: I don't think we need another revision of this patch, it is like
>>>> this for a good reason.
>>>
>>> Slightly confusing, in another reply you said you are going to address
>>> my comment. So, is it doable?
>>
>> I don't think so.
>>
>> My previous reply, to the thread in 0/14, was prematurely made with the
>> incorrect assumption that it was a simple change.  Now, after really digging
>> in to the code, and attempting to do as you suggested, I have changed my
>> mind.
>
> Would the snippet below help with avoiding any kmalloc calls? At a quick
> look, it seems that it's only map_mat_entry() that ends up using
> kmalloc() calls. Alternatively, exporting map_madt_entry() may work as
> well.

I think making a non-static version of map_madt_entry() is the cleanest 
solution.  That works, so I will send a new version of the patch set 
that does that instead.

David.


>
> diff --git a/drivers/acpi/processor_core.c b/drivers/acpi/processor_core.c
> index 33a38d604630..77af0a7df914 100644
> --- a/drivers/acpi/processor_core.c
> +++ b/drivers/acpi/processor_core.c
> @@ -152,6 +152,9 @@ static phys_cpuid_t map_mat_entry(acpi_handle handle, int type, u32 acpi_id)
>   	struct acpi_subtable_header *header;
>   	phys_cpuid_t phys_id = PHYS_CPUID_INVALID;
>
> +	if (!acpi_gbl_permanent_mmap)
> +		return phys_id;
> +
>   	if (ACPI_FAILURE(acpi_evaluate_object(handle, "_MAT", NULL, &buffer)))
>   		goto exit;
>
>