From: "H. Peter Anvin" <hpa@zytor.com>
To: Simon Jeons <simon.jeons@gmail.com>
Cc: Frantisek Hrbata <fhrbata@redhat.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
tglx@linutronix.de, mingo@redhat.com, x86@kernel.org,
oleg@redhat.com, kamaleshb@in.ibm.com
Subject: Re: [PATCH] x86: add phys addr validity check for /dev/mem mmap
Date: Wed, 10 Apr 2013 19:48:50 -0700 [thread overview]
Message-ID: <51662492.1030100@zytor.com> (raw)
In-Reply-To: <5166229D.2090904@gmail.com>
On 04/10/2013 07:40 PM, Simon Jeons wrote:
> Hi H.Peter,
> On 04/04/2013 09:13 AM, H. Peter Anvin wrote:
>> On 04/03/2013 06:11 PM, Simon Jeons wrote:
>>> Why we consider boot_cpu_data.x86_phys_bits instead of e820 map here?
>>>
>> Because x86_phys_bits is what controls how much address space the
>> processor has. e820 tells us how much *RAM* the machine has, or
>> specifically, how much RAM the machine had on boot.
>
> I have 8GB memory in my machine, but when I accumulated every e820
> ranges which dump in dmesg, there are 25MB memory less then 8GB(1024*8)
> memory, why 25MB miss?
>
For whatever reason your BIOS is stealing some memory, possibly for video.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
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WARNING: multiple messages have this Message-ID (diff)
From: "H. Peter Anvin" <hpa@zytor.com>
To: Simon Jeons <simon.jeons@gmail.com>
Cc: Frantisek Hrbata <fhrbata@redhat.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
tglx@linutronix.de, mingo@redhat.com, x86@kernel.org,
oleg@redhat.com, kamaleshb@in.ibm.com
Subject: Re: [PATCH] x86: add phys addr validity check for /dev/mem mmap
Date: Wed, 10 Apr 2013 19:48:50 -0700 [thread overview]
Message-ID: <51662492.1030100@zytor.com> (raw)
In-Reply-To: <5166229D.2090904@gmail.com>
On 04/10/2013 07:40 PM, Simon Jeons wrote:
> Hi H.Peter,
> On 04/04/2013 09:13 AM, H. Peter Anvin wrote:
>> On 04/03/2013 06:11 PM, Simon Jeons wrote:
>>> Why we consider boot_cpu_data.x86_phys_bits instead of e820 map here?
>>>
>> Because x86_phys_bits is what controls how much address space the
>> processor has. e820 tells us how much *RAM* the machine has, or
>> specifically, how much RAM the machine had on boot.
>
> I have 8GB memory in my machine, but when I accumulated every e820
> ranges which dump in dmesg, there are 25MB memory less then 8GB(1024*8)
> memory, why 25MB miss?
>
For whatever reason your BIOS is stealing some memory, possibly for video.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
next prev parent reply other threads:[~2013-04-11 2:49 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-02 12:28 [PATCH] x86: add phys addr validity check for /dev/mem mmap Frantisek Hrbata
2013-04-02 12:28 ` Frantisek Hrbata
2013-04-02 18:02 ` Oleg Nesterov
2013-04-02 18:02 ` Oleg Nesterov
2013-04-02 18:48 ` H. Peter Anvin
2013-04-02 18:48 ` H. Peter Anvin
2013-04-02 19:10 ` Frantisek Hrbata
2013-04-02 19:10 ` Frantisek Hrbata
2013-04-02 20:29 ` H. Peter Anvin
2013-04-02 20:29 ` H. Peter Anvin
2013-04-02 20:52 ` Frantisek Hrbata
2013-04-02 20:52 ` Frantisek Hrbata
2013-04-24 11:36 ` Frantisek Hrbata
2013-04-24 11:36 ` Frantisek Hrbata
2013-04-04 1:11 ` Simon Jeons
2013-04-04 1:11 ` Simon Jeons
2013-04-04 1:13 ` H. Peter Anvin
2013-04-04 1:13 ` H. Peter Anvin
2013-04-04 1:17 ` Simon Jeons
2013-04-04 1:17 ` Simon Jeons
2013-04-04 1:32 ` H. Peter Anvin
2013-04-04 1:32 ` H. Peter Anvin
2013-04-04 1:53 ` Simon Jeons
2013-04-04 1:53 ` Simon Jeons
2013-04-04 2:14 ` H. Peter Anvin
2013-04-04 2:14 ` H. Peter Anvin
2013-04-04 2:17 ` Simon Jeons
2013-04-04 2:17 ` Simon Jeons
2013-04-04 5:20 ` Simon Jeons
2013-04-04 5:20 ` Simon Jeons
2013-04-11 2:40 ` Simon Jeons
2013-04-11 2:40 ` Simon Jeons
2013-04-11 2:48 ` H. Peter Anvin [this message]
2013-04-11 2:48 ` H. Peter Anvin
2013-04-11 2:58 ` Simon Jeons
2013-04-11 2:58 ` Simon Jeons
2013-04-03 2:46 ` Cheng Jie He
2013-04-26 5:21 ` Will Huck
2013-04-26 5:21 ` Will Huck
2013-04-26 15:35 ` Frantisek Hrbata
2013-04-26 15:35 ` Frantisek Hrbata
2013-04-27 7:00 ` Will Huck
2013-04-27 7:00 ` Will Huck
2013-04-27 19:13 ` Frantisek Hrbata
2013-04-27 19:13 ` Frantisek Hrbata
2013-04-28 3:17 ` Will Huck
2013-04-28 3:17 ` Will Huck
2013-04-28 4:00 ` H. Peter Anvin
2013-04-28 4:00 ` H. Peter Anvin
2013-04-28 8:03 ` Will Huck
2013-04-28 8:03 ` Will Huck
2013-05-01 18:19 ` Dave Hansen
2013-05-01 18:19 ` Dave Hansen
2013-05-01 19:04 ` Frantisek Hrbata
2013-05-01 19:04 ` Frantisek Hrbata
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