On Tue, Jul 28, 2020 at 12:19:03PM +0000, Song Bao Hua (Barry Song) wrote:

I am sorry I haven't got your point yet. Do you mean something like the below?

arch/arm64/Kconfig:
config CMDLINE
	string "Default kernel command string"
-	default ""
+	default "pernuma_cma=16M"
	help
	  Provide a set of default command-line options at build time by
	  entering them here. As a minimum, you should specify the the
	  root device (e.g. root=/dev/nfs).

Yes.

A background of the current code is that Linux distributions can usually use arch/arm64/configs/defconfig
directly to build kernel. cmdline can be easily ignored during the generation of Linux distributions.

I've not actually heard of a distro shipping defconfig yet..

quoted

if a way to expose this in the device tree might be useful, but people
more familiar with the device tree and the arm code will have to chime
in on that.

Not sure if it is an useful user case as we are using ACPI but not device tree since it is an ARM64
server with NUMA.

Well, than maybe ACPI experts need to chime in on this.

quoted

This seems to have lost the dma_contiguous_default_area NULL check.

cma_alloc() is doing the check by returning NULL if cma is NULL.

struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
		       bool no_warn)
{
	...
	if (!cma || !cma->count)
		return NULL;
}

But I agree here the code can check before calling cma_alloc_aligned.

Oh, indeed.  Please split the removal of the NULL check in to a prep
patch then.

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