[Qemu-devel] [PATCH] Make -kernel flag optional on ARM.

[Qemu-devel] [PATCH] Make -kernel flag optional on ARM.

[Grant Likely]

Sometimes we want to boot the system via firmware instead of loading a
kernel into ram with the -kernel parameter. This patch makes the -kernel
parameter optional so that a bios image provided by the -pflash flag
will be executed.

For example:
qemu-system-arm -M vexpress-a15 -pflash <filename>

Note: Currently the file must be at least the size of the emulated flash
device (64M) otherwise QEMU will silently not use the data. This will be
fixed in a separate patch

This is part of the larger solution. For this to work it requires the
platform to have flash mapped or aliased to address 0 so that there is
some code for the emulator to execute.

Signed-off-by: Grant Likely <grant.likely@linaro.org>
Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: qemu-devel@nongnu.org
---

 hw/arm/boot.c | 47 ++++++++++++++++++++++-------------------------
 1 file changed, 22 insertions(+), 25 deletions(-)

diff --git a/hw/arm/boot.c b/hw/arm/boot.c
index 7c0090f..3b9e108 100644
--- a/hw/arm/boot.c
+++ b/hw/arm/boot.c
@@ -361,12 +361,6 @@ void arm_load_kernel(ARMCPU *cpu, struct arm_boot_info *info)
     int big_endian;
     QemuOpts *machine_opts;
 
-    /* Load the kernel.  */
-    if (!info->kernel_filename) {
-        fprintf(stderr, "Kernel image must be specified\n");
-        exit(1);
-    }
-
     machine_opts = qemu_opts_find(qemu_find_opts("machine"), 0);
     if (machine_opts) {
         info->dtb_filename = qemu_opt_get(machine_opts, "dtb");
@@ -403,26 +397,29 @@ void arm_load_kernel(ARMCPU *cpu, struct arm_boot_info *info)
     info->initrd_start = info->loader_start +
         MIN(info->ram_size / 2, 128 * 1024 * 1024);
 
-    /* Assume that raw images are linux kernels, and ELF images are not.  */
-    kernel_size = load_elf(info->kernel_filename, NULL, NULL, &elf_entry,
-                           NULL, NULL, big_endian, ELF_MACHINE, 1);
-    entry = elf_entry;
-    if (kernel_size < 0) {
-        kernel_size = load_uimage(info->kernel_filename, &entry, NULL,
-                                  &is_linux);
-    }
-    if (kernel_size < 0) {
-        entry = info->loader_start + KERNEL_LOAD_ADDR;
-        kernel_size = load_image_targphys(info->kernel_filename, entry,
-                                          info->ram_size - KERNEL_LOAD_ADDR);
-        is_linux = 1;
-    }
-    if (kernel_size < 0) {
-        fprintf(stderr, "qemu: could not load kernel '%s'\n",
-                info->kernel_filename);
-        exit(1);
+    if (info->kernel_filename) {
+        /* Assume that raw images are linux kernels, and ELF images are not.  */
+        kernel_size = load_elf(info->kernel_filename, NULL, NULL, &elf_entry,
+                               NULL, NULL, big_endian, ELF_MACHINE, 1);
+        entry = elf_entry;
+        if (kernel_size < 0) {
+            kernel_size = load_uimage(info->kernel_filename, &entry, NULL,
+                                      &is_linux);
+        }
+        if (kernel_size < 0) {
+            entry = info->loader_start + KERNEL_LOAD_ADDR;
+            kernel_size = load_image_targphys(info->kernel_filename, entry,
+                                              info->ram_size - KERNEL_LOAD_ADDR);
+            is_linux = 1;
+        }
+        if (kernel_size < 0) {
+            fprintf(stderr, "qemu: could not load kernel '%s'\n",
+                    info->kernel_filename);
+            exit(1);
+        }
+        info->entry = entry;
     }
-    info->entry = entry;
+
     if (is_linux) {
         if (info->initrd_filename) {
             initrd_size = load_image_targphys(info->initrd_filename,
-- 
1.8.1.2

Re: [Qemu-devel] [PATCH] Make -kernel flag optional on ARM.

[Peter Maydell]

On 10 July 2013 08:33, Grant Likely <grant.likely@linaro.org> wrote:
> Sometimes we want to boot the system via firmware instead of loading a
> kernel into ram with the -kernel parameter. This patch makes the -kernel
> parameter optional so that a bios image provided by the -pflash flag
> will be executed.
>
> For example:
> qemu-system-arm -M vexpress-a15 -pflash <filename>
>
> Note: Currently the file must be at least the size of the emulated flash
> device (64M) otherwise QEMU will silently not use the data. This will be
> fixed in a separate patch
>
> This is part of the larger solution. For this to work it requires the
> platform to have flash mapped or aliased to address 0 so that there is
> some code for the emulator to execute.

That patch is already on list :-)

> Signed-off-by: Grant Likely <grant.likely@linaro.org>
> Cc: Peter Maydell <peter.maydell@linaro.org>
> Cc: qemu-devel@nongnu.org
> ---
>
>  hw/arm/boot.c | 47 ++++++++++++++++++++++-------------------------
>  1 file changed, 22 insertions(+), 25 deletions(-)
>
> diff --git a/hw/arm/boot.c b/hw/arm/boot.c
> index 7c0090f..3b9e108 100644
> --- a/hw/arm/boot.c
> +++ b/hw/arm/boot.c
> @@ -361,12 +361,6 @@ void arm_load_kernel(ARMCPU *cpu, struct arm_boot_info *info)
>      int big_endian;
>      QemuOpts *machine_opts;
>
> -    /* Load the kernel.  */
> -    if (!info->kernel_filename) {
> -        fprintf(stderr, "Kernel image must be specified\n");
> -        exit(1);
> -    }

Why can't we just return from the function here? If we don't
have a kernel we can assume we don't have a dtb or an initrd
either. I don't think we want to do any of the other weird
stuff with setting up a reset handler or boot pen for the
secondary CPUs either -- we should just assume the bootrom
image in the flash handles this.

thanks
-- PMM

Re: [Qemu-devel] [PATCH] Make -kernel flag optional on ARM.

[Grant Likely]

On Wed, Jul 10, 2013 at 8:44 AM, Peter Maydell <peter.maydell@linaro.org> wrote:
> On 10 July 2013 08:33, Grant Likely <grant.likely@linaro.org> wrote:
>> Sometimes we want to boot the system via firmware instead of loading a
>> kernel into ram with the -kernel parameter. This patch makes the -kernel
>> parameter optional so that a bios image provided by the -pflash flag
>> will be executed.
>>
>> For example:
>> qemu-system-arm -M vexpress-a15 -pflash <filename>
>>
>> Note: Currently the file must be at least the size of the emulated flash
>> device (64M) otherwise QEMU will silently not use the data. This will be
>> fixed in a separate patch
>>
>> This is part of the larger solution. For this to work it requires the
>> platform to have flash mapped or aliased to address 0 so that there is
>> some code for the emulator to execute.
>
> That patch is already on list :-)

Heh, I wrote the above before grabbing and testing your patch.

>> diff --git a/hw/arm/boot.c b/hw/arm/boot.c
>> index 7c0090f..3b9e108 100644
>> --- a/hw/arm/boot.c
>> +++ b/hw/arm/boot.c
>> @@ -361,12 +361,6 @@ void arm_load_kernel(ARMCPU *cpu, struct arm_boot_info *info)
>>      int big_endian;
>>      QemuOpts *machine_opts;
>>
>> -    /* Load the kernel.  */
>> -    if (!info->kernel_filename) {
>> -        fprintf(stderr, "Kernel image must be specified\n");
>> -        exit(1);
>> -    }
>
> Why can't we just return from the function here? If we don't
> have a kernel we can assume we don't have a dtb or an initrd
> either. I don't think we want to do any of the other weird
> stuff with setting up a reset handler or boot pen for the
> secondary CPUs either -- we should just assume the bootrom
> image in the flash handles this.

I've just tested this, and you're right. I assumed that some of the
other stuff would be necessary, but it does work just fine to return.
Second version of the patch posted now.

g.