From: Anthony Liguori <anthony@codemonkey.ws>
To: Alexander Graf <agraf@suse.de>
Cc: Peter Maydell <peter.maydell@linaro.org>,
qemu-devel@nongnu.org, Rob Herring <rob.herring@calxeda.com>,
Grant Likely <grant.likely@secretlab.ca>,
Paul Brook <paul@codesourcery.com>,
"Edgar E. Iglesias" <edgar.iglesias@gmail.com>,
Jeremy Kerr <jeremy.kerr@canonical.com>,
John Williams <john.williams@petalogix.com>
Subject: Re: [Qemu-devel] [PATCH v2] arm: add device tree support
Date: Wed, 01 Feb 2012 07:44:27 -0600 [thread overview]
Message-ID: <4F2941BB.9010406@codemonkey.ws> (raw)
In-Reply-To: <514AF576-4462-40FD-B6EA-F98C6AD4A915@suse.de>
On 02/01/2012 07:32 AM, Alexander Graf wrote:
>
> On 01.02.2012, at 14:25, Anthony Liguori wrote:
>
>> On 02/01/2012 07:10 AM, Peter Maydell wrote:
>>> On 1 February 2012 13:04, Anthony Liguori<anthony@codemonkey.ws> wrote:
>>>> How does it race? Devices normally never touch memory so a loader device
>>>> will be the only thing mucking with memory.
>>>
>>> The obvious one is "loader reset function wants to set starting PC to
>>> entry point of kernel/etc" vs "CPU device reset wants to set starting
>>> PC to hardware-mandated reset vector". We have this at the moment, of
>>> course, and I think we implicitly rely on reset handlers being called
>>> in order of registration...
>>
>> I'm a bit confused, why can't the kernel loader be implemented in terms of a firmware blob?
>>
>> This is what we do for x86 and it solves this problem robustly. Isn't it just a matter of a few instructions to do a jmp to a known location?
>
> Only if you have non-semi-hosted modes. For e500 for example, we don't have a bios flash region mapped through mmio available. So we would have to write the "jump to kernel" code into ram. But where in RAM? Linux starts at address 0, so that one's taken.
The processor has to have a defined sequence where IP is fixed to a specific
value, no?
How else would the real hardware bootstrap software?
Regards,
Anthony Liguori
>
> Alex
>
>
next prev parent reply other threads:[~2012-02-01 13:44 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-01 0:11 [Qemu-devel] [PATCH v2] arm: add device tree support Grant Likely
2012-02-01 1:10 ` Alexander Graf
2012-02-01 1:35 ` Paul Brook
2012-02-01 1:44 ` Alexander Graf
2012-02-01 2:37 ` Anthony Liguori
2012-02-01 2:40 ` John Williams
2012-02-01 13:04 ` Anthony Liguori
2012-02-01 13:10 ` Peter Maydell
2012-02-01 13:25 ` Anthony Liguori
2012-02-01 13:32 ` Alexander Graf
2012-02-01 13:44 ` Anthony Liguori [this message]
2012-02-01 13:49 ` Alexander Graf
2012-02-01 13:52 ` Anthony Liguori
2012-02-01 13:55 ` Alexander Graf
2012-02-01 15:13 ` Anthony Liguori
2012-02-01 17:38 ` Grant Likely
2012-02-01 20:59 ` Alexander Graf
2012-02-01 2:35 ` Anthony Liguori
2012-02-22 19:42 ` Peter Maydell
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