linux-kernel - Re: [RFC v2] memmap: introduce cmdline parameter "memmap=nn[KMG]$" without start addr

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Date:   Tue, 28 Jun 2022 08:52:00 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     lizhe.67@...edance.com, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com
Cc:     lizefan.x@...edance.com, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC v2] memmap: introduce cmdline parameter "memmap=nn[KMG]$"
 without start addr

On 6/28/22 05:45, lizhe.67@...edance.com wrote:
> From: Li Zhe <lizhe.67@...edance.com>
> 
> In current kernel we can use memmap=nn[KMG]$ss[KMG] to reserve an
> area of memory for userspace usage through /dev/mem. We have to
> determine the start addr and length. In our scenario, we need
> reserve or alloc large continuous physical memory at least 256M in
> 512G's machine, and need reserve more memory in larger machine, at
> just boot phase for a userspace program. And these memories will not
> be freed to system before system reboot. The userspace program can
> use the memory through /dev/mem to store some data. Besides, a
> hardware will need the data stored by the userspace program to do
> it's job. Why we need continuous memory is that the hardware can
> only access memory without mmu.

That's still a rather anemic description.

I don't think we want this code in the kernel with that description, sorry.

If you'd like to come back with an actual description, naming the exact
hardware that you have *AND* explaining sane reasons for why the
hardware doesn't have a normal kernel driver (or interface) like every
other piece of hardware, then we can talk.  But, otherwise, this isn't
something that can go upstream.