Re: [Qemu-arm] [PATCH 4/7] m25p80: add a m25p80_set_rom_storage() routine

[Cédric Le Goater]

On 09/23/2016 10:17 AM, Peter Maydell wrote:
> On 23 September 2016 at 08:19, Cédric Le Goater <address@hidden> wrote:
>> But the goal is to boot from the device, so I added a memory region alias
>> at 0 to trigger the flash module mmios at boot time, as this is where
>> u-boot expects to be.
>>
>> and I fell in this trap :/
>>
>>         aspeed_smc_flash_read: To 0x0 of size 1: 0xbe mode:0
>>         Bad ram pointer (nil)
>>         Aborted (core dumped)
>>
>> There is a failure in get_page_addr_code(), possibly because qemu uses
>> byte per byte reads of the code (cpu_ldub_code). But this is beyond my
>> understanding of qemu's internal.
> 
> This is a bug in how we report the problem, but the underlying
> issue here is attempting to execute from something that's not RAM
> or ROM. You can't execute code out of something backed by MMIO.

OK. So I see two solutions. T

The "brutal" one which is to copy the flash contents in a rom blob 
at 0, but there is still an issue in getting access to the storage 
anyhow, as it is internal to m25p80. Or we should get the name of the 
backing file of the drive but I am not sure we are expected to do 
that as I don't see any API for it.

The other solution is something like this patch which lets the storage 
of the flash device be assigned externally. 


Thanks,

C.