feat: add support for efuse in qemu

[horw]

Closes #269

[horw]

@hfudev Hello! This MR has added support for qemu efuse.

[hfudev]

@igrr PTAL, thanks!

[igrr]

When launching QEMU and expecting that it should communicate with another application, it is better to use -daemonize flag — as recommended by QEMU documentation. Otherwise there may be a race condition between QEMU getting ready to accept TCP connections and the launch of the other application. It seems child.expect('qemu') aims to work around that, but I am not sure this is reliable enough.

[igrr]

Also, now that I'm thinking of this... don't you end up with two QEMU processes running at the same time, and accessing the same eFuse file?.. One QEMU process is already launched when dut is created, another one is launched here.

[achxkloel]

When launching QEMU and expecting that it should communicate with another application, it is better to use -daemonize flag — as recommended by QEMU documentation. Otherwise there may be a race condition between QEMU getting ready to accept TCP connections and the launch of the other application. It seems child.expect('qemu') aims to work around that, but I am not sure this is reliable enough.

I think solution using pexpect and nowait flag is reliable enough. Once qemu appears in the output, it indicates that QEMU is ready to accept connections. Another solution using -daemonize also works:

run_qemu_command = [
    '-daemonize',
    '-display',
    'none',
    '-machine',
    self.app.target,
    '-drive',
    f'file={self.image_path},if=mtd,format=raw',
    '-global',
    self.QEMU_STRAP_MODE_FMT.format(self.app.target, QEMU_TARGETS[self.app.target].strap_mode),
    '-drive',
    f'file={self.efuse_path},if=none,format=raw,id=efuse',
    '-global',
    f'driver=nvram.{self.app.target}.efuse,property=drive,value=efuse',
    '-serial',
    f'tcp::{available_port},server,nowait',
]
try:
    proc = subprocess.run(
        [self.current_qemu_executable_path, *run_qemu_command],
        check=True
    )
    res = shlex.split(command)

    ...

But I suggest to keep the current implementation.

[achxkloel]

Also, now that I'm thinking of this... don't you end up with two QEMU processes running at the same time, and accessing the same eFuse file?.. One QEMU process is already launched when dut is created, another one is launched here.

Yes, but the first process never writes to the eFuse file. All write operations are performed via TCP using espefuse. So it should be ok.

[achxkloel]

@igrr @hfudev Hello, PTAL

[hfudev]

LGTM!

[hfudev]

@igrr PTAL again. Thank you!

[hfudev]

Two Wokwi tests are failing due to missing access to secrets. These failures are unrelated to the current changes.

[horw]

@achxkloel Thank you!

[horw]

@hfudev Let's merge it first, and if there are any requests for improvement/bug, we can just fix them?