From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51827) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bnK3B-0005Zw-0a for qemu-devel@nongnu.org; Fri, 23 Sep 2016 02:33:34 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bnK37-0005Vd-VW for qemu-devel@nongnu.org; Fri, 23 Sep 2016 02:33:31 -0400 Received: from metis.ext.4.pengutronix.de ([92.198.50.35]:33941) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bnK37-0005SP-OX for qemu-devel@nongnu.org; Fri, 23 Sep 2016 02:33:29 -0400 Date: Fri, 23 Sep 2016 08:33:17 +0200 From: Michael Olbrich Message-ID: <20160923063317.kmsbek755fcun5ea@pengutronix.de> References: <1473520054-402-1-git-send-email-m.olbrich@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] [PATCH] hw/arm/boot: allow using a command line specified dtb without a kernel List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Maydell Cc: Paolo Bonzini , qemu-arm , QEMU Developers On Thu, Sep 22, 2016 at 05:23:17PM +0100, Peter Maydell wrote: > On 10 September 2016 at 16:07, Michael Olbrich wrote: > > When kernel and device tree are specified in the QEMU commandline, then > > this device tree may be modified e.g. to add virtio_mmio devices. > > With a bootloader e.g. on a flash device these extra devices are not > > available. > > With this change, the device tree can be specified at the QEMU commandline. > > The modified device tree made available to the bootloader with the same > > mechanism already supported by device trees fully generated by QEMU. > > Would you mind explaining your usecase in a little more detail > (for instance which machine model are you using) ? I'm using qemu for system integration testing. Including some bootloader / Linux kernel and userspace interaction. I'm currently using vexpress-a9 but I plan to investigate if the new imx6 machine is suitable for my use-case. In a setup without bootloader I already use a 9p rootfs. It's great for debugging and a lot easier to set up than networking and a NFS server. With this patch (and some bootloader patches to handle the device tree) I can do the same when a bootloader is involved. > > Signed-off-by: Michael Olbrich > > --- > > hw/arm/boot.c | 4 ++-- > > vl.c | 5 ----- > > 2 files changed, 2 insertions(+), 7 deletions(-) > > > > diff --git a/hw/arm/boot.c b/hw/arm/boot.c > > index 1b913a43ca65..942416d95a6f 100644 > > --- a/hw/arm/boot.c > > +++ b/hw/arm/boot.c > > @@ -773,6 +773,8 @@ static void arm_load_kernel_notify(Notifier *notifier, void *data) > > */ > > assert(!(info->secure_board_setup && kvm_enabled())); > > > > + info->dtb_filename = qemu_opt_get(qemu_get_machine_opts(), "dtb"); > > + > > /* Load the kernel. */ > > if (!info->kernel_filename || info->firmware_loaded) { > > > > @@ -833,8 +835,6 @@ static void arm_load_kernel_notify(Notifier *notifier, void *data) > > elf_machine = EM_ARM; > > } > > > > - info->dtb_filename = qemu_opt_get(qemu_get_machine_opts(), "dtb"); > > - > > if (!info->secondary_cpu_reset_hook) { > > info->secondary_cpu_reset_hook = default_reset_secondary; > > } > > This change definitely makes sense -- we check info->dtb_filename > in have_dtb() so we need to set it before we call that function, > not afterwards. > > > diff --git a/vl.c b/vl.c > > index ee557a1d3f8a..bbea51e0ce7d 100644 > > --- a/vl.c > > +++ b/vl.c > > @@ -4335,11 +4335,6 @@ int main(int argc, char **argv, char **envp) > > exit(1); > > } > > > > - if (!linux_boot && qemu_opt_get(machine_opts, "dtb")) { > > - error_report("-dtb only allowed with -kernel option"); > > - exit(1); > > - } > > - > > I can see why you want this change, but what worries me a little > is that this is changing the behaviour of -dtb for all QEMU > target architectures, not just ARM (they no longer get a helpful > message on user error). I'm not sure how to address that, though. Would a 'if !arm' be possible or useful here? Michael -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |