Re: [Xen-devel] Odgovor: Basic bare metal ARM domain interface

[Julien Grall <julien.grall@xxxxxxx>]

On 30/05/16 21:21, Ivan Pavić2 wrote:
> Hello,
Hello Ivan,

Sorry for the late answer.

> > > I used FreeRTOS code for console output. It is based on Mini OS code. There are 
> > > two problems as I've >determined
> > > with debugging. First is that vsnprintf blocks for some reason in print 
> > > function so i commented it out. After the
> > snprintf blocks...
> > > hypercall function blocked as well. I modified hypercall function so it looks 
> > > like this:
> > > (void)HYPERVISOR_console_io(CONSOLEIO_write, 3, "yes");
> > As the call failed I decided to make hypervisor call directly in boot procedure, 
> > so I put this assembler code just >before
> > branch to main:
> >         mov r12, #18 ; console io code
> >         mov r0, #0 ; write operation(first parameter)
> >         mov r1, #5 ; length of message (second parameter)
> >        ldr r2, =msg ; message address (third parameter)
> >         .long 0xe140ea71 ; hvc instruction
> >         b main ; branch to main
For your information, hypervisor calls have to be done with data cache 
enabled. Otherwise you not may get garbage (or nothing at all) on the 
console.
> > msg is defined as:
> > msg:
> >     .asciz "hello"
> > I get deadbeef in registers, apperently something happened (xenctx output):
> > PC:       4000c5bc
> > CPSR:     600001f3
> > USR:               SP:00000000 LR:00000000
> > SVC: SPSR:00000000 SP:4011c200 LR:400080a8
> > FIQ: SPSR:00000000 SP:40124200 LR:00000000
> > IRQ: SPSR:00000000 SP:40120200 LR:00000000
> > ABT: SPSR:00000000 SP:40128200 LR:00000000
> > UND: SPSR:00000000 SP:4012c200 LR:00000000
>   >r0_usr: 00000000        r1_usr: deadbeef        r2_usr: deadbeef
>   >r3_usr: 00000000        r4_usr: 00000000        r5_usr: 00000000
>   >r6_usr: 00000000        r7_usr: 00000000        r8_usr: 00000000
>   >r9_usr: 00000064       r10_usr: 00000064       r11_usr: 00000000
> > r12_usr: deadbeef
>
> > According to arch-arm.h r0 is return value of call. It is 0, operation 
> > successful???? Still I don't get output on
> > console...
> > Thank you in advance,
> > Regards,
> > Ivan Pavic
> I still didn't solve why I don't see no output on emergency console, I think I 
> should because if deadbeef in registers it
> do_console_io should have been called.
The emergency console and any Xen debug facilities (hvc 0xffxx) only 
works when the hypervisor has been built with debug enabled.
By default, release version are built with debug disabled. You will have 
to pass debug=y on the build command line to enable debug.
> However new problem emerged i tried to add iomem
> parameter in configuration file to get access over gpio but domain won't start 
> because operation is not permitted.
> Should I somehow release disable that memory space for dom0, perhaps in dts for 
> dom0?
>
> Snippet from dom.cfg file:
>
> iomem = ["0x13400000,1@0x41400000"]
>
> 0x13400000 is base address of GPIO that I want to use.
iomem expects a physical page number (see the documentation in 
docs/man/xl.cfg.pod.5). So it should be:
iomem = ["0x13400,1@0x41400"]

> I get this error: (snippet from xl -vvv create -c dom.cfg)
>
> libxl: debug: libxl_create.c:1213:domcreate_launch_dm: dom4 iomem 
> 13400000-13400000
> libxl: error: libxl_create.c:1220:domcreate_launch_dm: failed give dom4 access 
> to iomem range 13400000-13400000: Operation not permitted
> libxl: debug: libxl.c:1719:devices_destroy_cb: forked pid 3835 for destroy of 
> domain 4
>
> Thank you in advance,
Regards,

--
Julien Grall

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