Hi,

I'm not sure whether my comments can help you or not.

I also asked a similar question to the community.

The related articles are as follows:

http://sourceforge.net/p/genode/mailman/message/34341641/

I modified my source code referring to the above link.

Based on the answers from the community, I used the "dma_alloc_coherent()" as follows in the device driver in the Normal World:

/* variables for buffer */

static dma_addr_t genblk_buf_phys;

static void * genblk_buf

genblk_buf = dma_alloc_coherent(NULL, 1024, &genblk_buf_phys, GFP_KERNEL);

/* send smc instruction to initialize buffer */

smc_blk(instruction_id, genblk_buf_phys, 1024);

In the Secure World, tz_vmm was modified to handle this as follows:

/* variables for buffer */

void * _buf;

Genode::size_t _buf_size;

addr_t buf_base;

addr_t buf_top, ram_top, buf_off;

Ram * ram;

bool buf_err;

buf_base = (addr_t)_vm->state()->r1;

_buf_size = (Genode::size_t)_vm->state()->r2;

buf_top = buf_base + _buf_size;

ram = _vm->ram();

ram_top = ram->base() + ram->size();

buf_err = buf_top <= buf_base;

buf_err |= buf_base < ram->base();

buf_err |= buf_top >= ram_top;

if (buf_err) {

PERR("blk: illegal buffer constraints");

break;

}

buf_off = buf_base - ram->base();

_buf = (void *)(ram->local() + buf_off);

After this, _buf is used to refer the shared buffer in the Secure World, and genblk_buf is used in the Normal World.

I hope my humble comments can help you.

Jaemin Park.

On Thu, Dec 10, 2015 at 1:15 AM, Stefan Brenner <brenner@...290...> wrote:

Hi,

currently we're working with the TrustZone VMM example from Genode based
on Genode 15.05 on i.MX53 QSB.

We have a shared buffer in normal world, which we want to use for
cross-world communication.

Currently the buffer is allocated using mmap MAP_SHARED | MAP_ANON.

We're having strange issues/problems/inconsistencies when accessing the
memory range in Genode (secure world) after normal world has written to it.

We read that uncached memory should be used for this, or the cache lines
have to be flushed/invalidated. However, apparently we can't get either
of these options working.

So our questions as follows:

1) We use mmap(NULL, <size>, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANON,
-1, 0) to allocate the buffer in normal world (Linux). Is there a better
way to allocate uncached memory?

2) We've tried __cpuc_flush_user_all(), __cpuc_flush_kern_all() in order
to invalidate all cache lines (later maybe only the affected cache lines
once this works in general). Is this correct, to do this in normal world
(i.e. Linux)?

3) At the moment we assume that Genode doesn't have to invalidate/flush
its cache lines because as it is the VMM it should be aware of the fact
that the cache might be stale.

Any help is appreciated. A short hint: Currently our idea is to send an
hypercall to the Genode VMM after Linux has written to the buffer, so
Genode will pretty quickly access the memory after it has been written
to from Linux.

Best regards, Stefan.

--
M.Sc. Stefan Brenner
Institute of Operating Systems and Computer Networks
Distributed Systems Group
TU Braunschweig

www: https://www.ibr.cs.tu-bs.de/users/brenner
mail: brenner@...290...

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