Hi Fernando,

Thanks a lot for the help. This makes perfect sense. I was able to create 
/dev/mem node on cut-down image and able to access my device so didnt try to 
speed up the simulation using KVM CPU models but it would be super cool to get 
that working on x86 host :)

Regards,uzair

Date: Tue, 26 Jan 2016 10:25:15 +0100
From: [email protected]
To: [email protected]
Subject: Re: [gem5-users] Access devices on gem5 full system booting cut down 
linux image

Hello,

> b) is it possible to use ArmKVMCPU model on x86 host via QEMU ARM 
virtualization?? I was thinking to emulate ARM platform on my linux-x86 
host first and then run gem5 in that QEMU VM. Can I use ArmKVMCPU in 
that case because if I can then I expect some speed improvements

Qemu does not support the hyp mode, needed by KVM in the guest O.S. I tried the 
ARM Foundation model, gem5 compiles and recognizes /dev/kvm, but I got a kernel 
panic:
[  723.264945] Internal error: Oops - undefined instruction: 0 [#1] PREEMPT SMP
...
[  738.399492] Call trace:
[  738.481415] [<ffffffc00040fe04>] arch_timer_handler_phys+0x8/0x38
[  738.678133] [<ffffffc0000d9344>] handle_percpu_devid_irq+0x90/0xb8
[  738.877690] [<ffffffc0000d5528>] generic_handle_irq+0x30/0x4c
[  739.063491] [<ffffffc0000848bc>] handle_IRQ+0x68/0xe4
[  739.227484] [<ffffffc000081290>] gic_handle_irq+0x38/0x7c
...

I'm not aware if this panic was caused by something not modeled in ARM 
Foundation or by something broken in the 3.16.0-rc6 kernel.

Hope it helps,
--
Fernando A. Endo, Post-doc

INRIA Rennes-Bretagne Atlantique
France



2016-01-14 11:55 GMT+01:00 Uzair Sharif <[email protected]>:



Hi,
I have managed to set up a simple i/o device in gem5 full system. But for 
accessing it I normally use linux mmap() utility but in the cut down disk image 
(linux-arm-ael.img) I cant see /dev/mem file. Can you guys suggest me an 
alternative approach to access my device on this cut down image or I have to 
modify the kernel/disk image??

I can use ubuntu image but it takes ~20 minutes to boot with atomic CPU model 
and makes SW dev. very time consuming. If I am to use this image can you give 
me pointers regarding speeding things up. I can think of these options:
a) make checkpoints and later somehow setup ssh connection with host PC so as 
to port new SW on to the disk image. Is networking possible for gem5 system??
b) is it possible to use ArmKVMCPU model on x86 host via QEMU ARM 
virtualization?? I was thinking to emulate ARM platform on my linux-x86 host 
first and then run gem5 in that QEMU VM. Can I use ArmKVMCPU in that case 
because if I can then I expect some speed improvements
c) I read in Android boot documentation that replacing cow disk image with raw 
disk image can help to improve the boot speed. I tried that approach for ubuntu 
image but I didnt see any speed improvements. Am i making any mistake??
Regards, uzair
                                          

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