RE: How to start an armv8 machine in EL3?

[ckim]

Hi, 
If my baremetal image size is bigger than 64MB, can I increase the pflash 
device size?
I tried changing VIRT_FLASH size in hw/arm/virt.c, but doesn't work.
BTW, VIRT_FLASH size seems to be 0x08000000 (128MB), but why is it limited to 
64MB?
Thanks!

Chan Kim

> -----Original Message-----
> From: Alex Bennée <alex.bennee@linaro.org>
> Sent: Wednesday, March 3, 2021 11:29 PM
> To: ckim@etri.re.kr
> Cc: qemu-discuss@nongnu.org
> Subject: Re: How to start an armv8 machine in EL3?
> 
> 
> ckim@etri.re.kr writes:
> 
> > Found out how to do it! (I needed secure=true).
> 
> Hmm I would hope true and on are synonyms... might have to poke that. I
> forgot about the gic-version, we should make that easier to get right.
> 
> > ${QEMU_DIR}/qemu-system-aarch64 -machine
> > type=virt,gic-version=3,secure=true -cpu cortex-a72 -nographic -smp 1
> > -m 2048 -drive if=pflash,file=pflash.img,format=raw,readonly=on -s -S
> > https://lists.gnu.org/archive/html/qemu-devel/2017-05/msg06622.html
> > Thanks!
> > Chan Kim
> >
> >> -----Original Message-----
> >> From: ckim@etri.re.kr <ckim@etri.re.kr>
> >> Sent: Wednesday, March 3, 2021 11:04 PM
> >> To: 'Alex Bennée' <alex.bennee@linaro.org>
> >> Cc: 'qemu-discuss@nongnu.org' <qemu-discuss@nongnu.org>
> >> Subject: RE: How to start an armv8 machine in EL3?
> >>
> >> Hi Alex Bennée,
> >>
> >> Sorry, machine ab21q is just the copy of machine virt.
> >> I found the pflash.img contained all zero in the beginning so it
> >> cause invalid instruction trap.
> >> (thanks for the -d int,exec,in_asm option, I have to first learn more
> >> about the qemu usage than the internal.) So I did 'cp test.bin
> >> pflash.img; truncate -s 67108864 pflash.img' to cut it to 64MB.
> >> (The test.bin was almost 67MB, I was confused by the small sized
> >> test.elf which was only 776KB).
> >> Now with the ' ${QEMU_DIR}/qemu-system-aarch64 -M virt -cpu
> >> cortex-a72 - nographic -smp 1 -m 2048 -drive
> >> if=pflash,file=pflash.img,format=raw,readonly=on -s -S' command, And
> >> after attaching gdb, I can see the original assembly code is being
> executed.
> >> But with this method, it still is in EL1 (I can see with 'mrs x8,
> >> currentel' shortly after the start), And the 'msr sp_el1, x0'
> >> instruction causes trap to 0x200.
> >> Could you give me more advice on this?
> >> Thank you very much.
> >>
> >> Chan Kim
> >>
> >> > -----Original Message-----
> >> > From: Alex Bennée <alex.bennee@linaro.org>
> >> > Sent: Wednesday, March 3, 2021 9:01 PM
> >> > To: ckim@etri.re.kr
> >> > Cc: qemu-discuss@nongnu.org
> >> > Subject: Re: How to start an armv8 machine in EL3?
> >> >
> >> >
> >> > ckim@etri.re.kr writes:
> >> >
> >> > > Hello Alex Bennée,
> >> > >
> >> > > Thank you for the help!
> >> > > I didn't know "-kernel xxx.elf" method makes it start at EL1 by
> >> > > the loader stub, and doing "--machine virtualization=on" makes it
> >> > > start at
> >> > EL2. I checked these using gdb.
> >> > >
> >> > > And then I tested your suggestion :
> >> > > ${QEMU_DIR}/qemu-system-aarch64 -M ab21q -cpu cortex-a72
> >> > > -nographic -smp 1 -m 2048 -drive
> >> > > if=pflash,file=${KER_DIR}/ab21s_test.bin,format=raw,readonly=on
> >> > > -s -S
> >> >
> >> > Hold on you've just switched from -M virt to -M ab21q? I don't even
> >> > recognise that model.
> >> >
> >> > > And it gave me :
> >> > > qemu-system-aarch64: device requires 67108864 bytes, block
> >> > > backend provides 776704 bytes
> >> > >
> >> > > Looks like the pflash device size is 64MB and my .bin file (which
> >> > > I made
> >> > with objcopy from .elf file) is not big enough to fill the device.
> >> > > I made the .bin file inside the pflash.img file by doing
> >> > > (https://xnand.netlify.app/2019/10/03/armv8-qemu-efi-aarch64.html
> >> > > )
> >> > >
> >> > >     cp ${KER_DIR}/ab21s_test.bin pflash.img
> >> > >     dd if=/dev/zero of=pflash.img bs=1c count=1 seek=67108863
> >> > >
> >> > > and tried
> >> > > ${QEMU_DIR}/qemu-system-aarch64 -M virt -cpu cortex-a72
> >> > > -nographic -smp 1 -m 2048 -drive
> >> > > if=pflash,file=pflash.img,format=raw,readonly=on -
> >> > s -S To see how the code works, but it traps from the first
> instruction.
> >> >
> >> > Is it the instruction you expect? Try single stepping with gdbstub
> >> > while using -d int,exec,in_asm on your command line for more details.
> >> >
> >> > >
> >> > > Can you tell me what's wrong with my command? (BTW I made .bin
> >> > > file by aarch64-elf-objcopy -O binary test.elf test.bin )
> >> > >
> >> > > Again thanks for the kind explanation!
> >> > > Best regards,
> >> > >
> >> > > Chan Kim
> >> > >
> >> > >> -----Original Message-----
> >> > >> From: Alex Bennée <alex.bennee@linaro.org>
> >> > >> Sent: Wednesday, March 3, 2021 7:05 PM
> >> > >> To: ckim@etri.re.kr
> >> > >> Cc: qemu-discuss@nongnu.org
> >> > >> Subject: Re: How to start an armv8 machine in EL3?
> >> > >>
> >> > >>
> >> > >> ckim@etri.re.kr writes:
> >> > >>
> >> > >> > Hello all,
> >> > >> >
> >> > >> > I found out in a baremetal program I run for qemu aarch64 'virt'
> >> > >> > machine (cpu is cortex-a72),
> >> > >> >
> >> > >> > the "msr sp_el1, x0" instruction causes trap making PC jump to
> >> > >> > 0x200 which is the vector address for synchronous exception,
> >> > >> > from current EL while using SP_ELx (if the vector base address
> >> > >> > was 0,
> >> > which is the case).
> >> > >> >
> >> > >> > (Ref :
> >> > >> > https://developer.arm.com/documentation/102412/0100/The-vector
> >> > >> > -ta
> >> > >> > bl
> >> > >> > es
> >> > >> > )
> >> > >> >
> >> > >> > When I read the 'EL' value by 'msr x8, currentel', x8 became
> '0x4'
> >> > >> > so it is
> >> > >> > EL1
> >> > >> > (https://community.arm.com/developer/ip-products/processors/f/
> >> > >> > cor
> >> > >> > te
> >> > >> > x-a
> >> > >> > -forum
> >> > >> > /10303/armv8-a-currentel-register-definition)
> >> > >> >
> >> > >> > How come cortex-a72 machines started at EL1?
> >> > >>
> >> > >> Are you booting a kernel directly? In this case the kernel will
> >> > >> boot into
> >> > >> EL1 unless you specify -machine type=virt,virtualization=on in
> >> > >> which case it will boot into EL2 and allow the kernel to utilise
> >> > >> the virtualisation extensions.
> >> > >>
> >> > >> > And if I want to make the virtual machine start at EL3 (this
> >> > >> > baremetal code assumes it should be in EL3 after reset, and it
> >> > >> > runs ok in rtl sim.), what should I do?
> >> > >>
> >> > >> Generally as only firmware deals with EL3 you would have it
> >> > >> running on some sort of flash device which the model would boot
> >> > >> to directly in EL3 rather than running the stub loader we have for
> the kernel.
> >> > >> For example to load the EDK firmware you would have:
> >> > >>
> >> > >>    -drive
> >> > >> if=pflash,file=/usr/share/AAVMF/AAVMF_CODE.fd,format=raw,readonl
> >> > >> y=on
> >> \
> >> > >>    -drive
> >> > >> if=pflash,file=/home/alex/models/qemu-arm64-efivars,format=raw
> >> > >>
> >> > >> as part of your command line. You also need to enable secure
> >> > >> mode in the machine options (-machine type=virt,secure=on).
> >> > >>
> >> > >> >
> >> > >> > Thank you very much for reading.
> >> > >> >
> >> > >> > Chan Kim
> >> > >> >
> >> > >> >
> >> > >>
> >> > >>
> >> > >> --
> >> > >> Alex Bennée
> >> >
> >> >
> >> > --
> >> > Alex Bennée
> 
> 
> --
> Alex Bennée