On 01/13/2017 10:36 AM, Alison Wang wrote:
On 01/13/2017 09:23 AM, Alison Wang wrote:
Am 13.01.2017 um 08:50 schrieb Alison Wang <b18...@freescale.com>:
For 64-bit kernel, there is a warning about x1-x3 nonzero in
violation
of boot protocol. x3 should be reset to zero before jumping to the
kernel.
This patch will adjust the parameters to transfer and make sure x3
is zero.
Signed-off-by: Alison Wang <alison.w...@nxp.com>
If x3 is part of the boot protocol, please treat it as function
argument rather than hard code it to 0.
[Alison Wang] I think x3 need to set to 0. Refer to the codes for the
warning in kernel,
if (boot_args[1] || boot_args[2] || boot_args[3]) {
pr_err("WARNING: x1-x3 nonzero in violation of boot
protocol:\n"
"\tx1: %016llx\n\tx2: %016llx\n\tx3: %016llx\n"
"This indicates a broken bootloader or old
kernel\n",
boot_args[1], boot_args[2], boot_args[3]);
}
Yes, that merely means that the kernel doesn't take 3 arguments, it
takes 4. Today args[1..3] have to be 0, but I don't want to iron that
out in u-boot code.
So in pseudo-code, what we do today is we call
entry(dt_addr, 0, 0);
and instead we should be calling
entry(dt_addr, 0, 0, 0);
So in U-Boot code that means we should change the prototype for our
switch function from
void armv8_switch_to_el2(u64 args, u64 mach_nr, u64 fdt_addr,
u64 entry_point, u64 es_flag);
to
void armv8_switch_to_el2(u64 args, u64 mach_nr, u64 fdt_addr,
u64 arg4, u64 entry_point, u64 es_flag);
and adapt the macros accordingly to use x5/x6 instead of x4/5.
[Alison Wang] I understand your meaning. Actually, I thought that method too.
Well, my concern is that there are more changes. Not only armv8_switch_to_el2
and armv8_switch_to_el1, all the places calling them need to change too. It may
cause more problems. With this concern, I choose a simple way to fix this issue
before.
I think there'll be enough people testing Linux boot :), let's try to
fix it properly right away.
Alex
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