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SubjectRe: [PATCH] x86: Setup early console as early as possible
On 07/12/2010 03:57 PM, Jeremy Fitzhardinge wrote:
> On 07/12/2010 11:11 AM, Yinghai Lu wrote:
>> On 07/12/2010 11:09 AM, H. Peter Anvin wrote:
>>
>>> On 07/12/2010 10:44 AM, Cyrill Gorcunov wrote:
>>>
>>>> Peter, while reviewing this patch I found another nit in
>>>> context of early_param usage, so the patch is below. It's
>>>> completely trivial. Actually I thought I've already fixed
>>>> all early_param cases long ago but this one somehow sneaked ;)
>>>>
>>>> Anyway, Yinghai, Peter,
>>>>
>>>> I'm not sure but can't we use some boot_param "pad" field for
>>>> "being copied" flag instead of new variable? There is a case
>>>> when boot_param is used as __initdata and I'm not sure we clear
>>>> this section explicitly.
>>>>
>>>>
>>> Actually, even better would be to simply use boot_params.hdr.version,
>>> which will never be zero.
>>>
>> Jeremy,
>>
>> any reason that xen cat not use x86_64_start_kernel directly?
>>
>
> As I remember it, I split x86_64_start_kernel into two pieces, one
> containing the bits that were awkward with Xen. I don't remember which
> were the problematic parts, but it all looks pretty tricky. Specifically:
>
> * Xen will pre-clear the bss, so that's not necessary
> * we don't go via head, so cleanup_highmap isn't either
> * PV domains don't have an IDT available to them, or any of their
> associated structures
>
> So the whole thing looks at best reundant, and at worst has the
> potential for causing subtle damage.
>
> Why do you ask? Does it relate to the early console stuff, or are you
> just asking because you're looking at it?

yes, make setup_early_console()/copy_bootdata two times....

and that looks strange.


+static int __initdata bootdata_copied;
static void __init copy_bootdata(char *real_mode_data)
{
char * command_line;

+ if (bootdata_copied)
+ return;
+
memcpy(&boot_params, real_mode_data, sizeof boot_params);
if (boot_params.hdr.cmd_line_ptr) {
command_line = __va(boot_params.hdr.cmd_line_ptr);
memcpy(boot_command_line, command_line, COMMAND_LINE_SIZE);
}
+
+ bootdata_copied = 1;
}

void __init x86_64_start_kernel(char * real_mode_data)
@@ -73,6 +80,10 @@ void __init x86_64_start_kernel(char * real_mode_data)
/* clear bss before set_intr_gate with early_idt_handler */
clear_bss();

+ /* boot_params is in bss */
+ copy_bootdata(__va(real_mode_data));
+ setup_early_console();
+
/* Make NULL pointers segfault */
zap_identity_mappings();

@@ -97,8 +108,11 @@ void __init x86_64_start_kernel(char * real_mode_data)
void __init x86_64_start_reservations(char *real_mode_data)
{
copy_bootdata(__va(real_mode_data));
+ setup_early_console();
+

Thanks

Yinghai Lu


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