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

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Message-ID: <de2500c4-fce4-31dc-29bc-aa3007027eb9@intel.com>
Date:   Thu, 23 Jun 2022 07:06:36 -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] memmap: introduce cmdline parameter "memmap=nn[KMG]$"
 without start addr

On 6/22/22 23:24, lizhe.67@...edance.com wrote:
> In our scenario, we need reserve or alloc large continous memory like
> 256M in machine which have different memory specification at just
> boot phase for a user land process.

Just marking the memory reserved doesn't do any good by itself.  There
must be some *other* kernel code to find this reserved area and make it
available to userspace.

It seems kinda silly to add this to the kernel without also adding the
other half of the solution.  Plus, we don't really even know what this
is for.  Are there other, better solutions?  I certainly can't offer any
because this changelog did not provide a full picture of the problem
this solves.