Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Thu, 23 Jun 2022 11:22:52 -0700
From:   "H. Peter Anvin" <hpa@zytor.com>
To:     Dave Hansen <dave.hansen@intel.com>, lizhe.67@bytedance.com,
        tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
        dave.hansen@linux.intel.com, x86@kernel.org
CC:     lizefan.x@bytedance.com, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: =?US-ASCII?Q?Re=3A_=5BRFC=5D_memmap=3A_introduce_cmdline_param?= =?US-ASCII?Q?eter_=22memmap=3Dnn=5BKMG=5D=24=22_without_start_addr?=
User-Agent: K-9 Mail for Android
In-Reply-To: <de2500c4-fce4-31dc-29bc-aa3007027eb9@intel.com>
References: <20220623062402.12392-1-lizhe.67@bytedance.com> <de2500c4-fce4-31dc-29bc-aa3007027eb9@intel.com>
Message-ID: <0EA9CBD4-D083-4546-BFAC-9C3A97420E5B@zytor.com>
MIME-Version: 1.0
Content-Type: text/plain;
 charset=utf-8
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On June 23, 2022 7:06:36 AM PDT, Dave Hansen <dave=2Ehansen@intel=2Ecom> wr=
ote:
>On 6/22/22 23:24, lizhe=2E67@bytedance=2Ecom 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=2E
>
>Just marking the memory reserved doesn't do any good by itself=2E  There
>must be some *other* kernel code to find this reserved area and make it
>available to userspace=2E
>
>It seems kinda silly to add this to the kernel without also adding the
>other half of the solution=2E  Plus, we don't really even know what this
>is for=2E  Are there other, better solutions?  I certainly can't offer an=
y
>because this changelog did not provide a full picture of the problem
>this solves=2E

Don't we already have a large contiguous physical memory allocator for thi=
s reason (misdesigned hardware?)