[PATCH] x86,setup: add serial_console_port_base in boot_params

[PATCH] x86,setup: add serial_console_port_base in boot_params

[Yinghai Lu]

to save the early_serial_base.

Also bootloader could fill that field, so setup code could reuse it.

decompress code could reuse early serial console from setup code.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>

---
 Documentation/x86/zero-page.txt  |    1 +
 arch/x86/boot/compressed/misc.c  |   25 +++++++++++++++++++++++++
 arch/x86/boot/tty.c              |    7 ++++++-
 arch/x86/include/asm/bootparam.h |    3 ++-
 4 files changed, 34 insertions(+), 2 deletions(-)

Index: linux-2.6/Documentation/x86/zero-page.txt
===================================================================
--- linux-2.6.orig/Documentation/x86/zero-page.txt
+++ linux-2.6/Documentation/x86/zero-page.txt
@@ -12,6 +12,7 @@ Offset	Proto	Name		Meaning
 000/040	ALL	screen_info	Text mode or frame buffer information
 				(struct screen_info)
 040/014	ALL	apm_bios_info	APM BIOS information (struct apm_bios_info)
+054/002 ALL	serial_console_port_base early serial console preset
 058/008	ALL	tboot_addr      Physical address of tboot shared page
 060/010	ALL	ist_info	Intel SpeedStep (IST) BIOS support information
 				(struct ist_info)
Index: linux-2.6/arch/x86/boot/compressed/misc.c
===================================================================
--- linux-2.6.orig/arch/x86/boot/compressed/misc.c
+++ linux-2.6/arch/x86/boot/compressed/misc.c
@@ -125,6 +125,11 @@ static void error(char *m);
  */
 static struct boot_params *real_mode;		/* Pointer to real-mode data */
 static int quiet;
+static int early_serial_base;
+
+#define XMTRDY          0x20
+#define TXR             0       /*  Transmit register (WRITE) */
+#define LSR             5       /*  Line Status               */
 
 void *memset(void *s, int c, size_t n);
 void *memcpy(void *dest, const void *src, size_t n);
@@ -170,6 +175,16 @@ static void scroll(void)
 		vidmem[i] = ' ';
 }
 
+static void serial_putchar(int ch)
+{
+	unsigned timeout = 0xffff;
+
+	while ((inb(early_serial_base + LSR) & XMTRDY) == 0 && --timeout)
+		cpu_relax();
+
+	outb(ch, early_serial_base + TXR);
+}
+
 static void __putstr(int error, const char *s)
 {
 	int x, y, pos;
@@ -179,6 +194,14 @@ static void __putstr(int error, const ch
 	if (!error)
 		return;
 #endif
+	if (early_serial_base) {
+		const char *str = s;
+		while (*str) {
+			if (*str == '\n')
+				serial_putchar('\r');
+			serial_putchar(*str++);
+		}
+	}
 
 	if (real_mode->screen_info.orig_video_mode == 0 &&
 	    lines == 0 && cols == 0)
@@ -319,6 +342,8 @@ asmlinkage void decompress_kernel(void *
 	lines = real_mode->screen_info.orig_video_lines;
 	cols = real_mode->screen_info.orig_video_cols;
 
+	early_serial_base = real_mode->serial_console_port_base;
+
 	free_mem_ptr     = heap;	/* Heap */
 	free_mem_end_ptr = heap + BOOT_HEAP_SIZE;
 
Index: linux-2.6/arch/x86/boot/tty.c
===================================================================
--- linux-2.6.orig/arch/x86/boot/tty.c
+++ linux-2.6/arch/x86/boot/tty.c
@@ -266,8 +266,13 @@ static void parse_console_uart8250(void)
 
 void console_init(void)
 {
-	parse_earlyprintk();
+	early_serial_base = boot_params.serial_console_port_base;
+
+	if (!early_serial_base)
+		parse_earlyprintk();
 
 	if (!early_serial_base)
 		parse_console_uart8250();
+
+	boot_params.serial_console_port_base = early_serial_base;
 }
Index: linux-2.6/arch/x86/include/asm/bootparam.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/bootparam.h
+++ linux-2.6/arch/x86/include/asm/bootparam.h
@@ -93,7 +93,8 @@ struct efi_info {
 struct boot_params {
 	struct screen_info screen_info;			/* 0x000 */
 	struct apm_bios_info apm_bios_info;		/* 0x040 */
-	__u8  _pad2[4];					/* 0x054 */
+	__u16  serial_console_port_base;		/* 0x054 */
+	__u8  _pad2[2];					/* 0x056 */
 	__u64  tboot_addr;				/* 0x058 */
 	struct ist_info ist_info;			/* 0x060 */
 	__u8  _pad3[16];				/* 0x070 */

Re: [PATCH] x86,setup: add serial_console_port_base in boot_params

[H. Peter Anvin]

On 07/15/2010 03:27 PM, Yinghai Lu wrote:
> 
> to save the early_serial_base.
> 
> Also bootloader could fill that field, so setup code could reuse it.
> 
> decompress code could reuse early serial console from setup code.
> 
> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
> 

What's the point with this over what we currently have?

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

Re: [PATCH] x86,setup: add serial_console_port_base in boot_params

[Yinghai Lu]

On 07/15/2010 05:12 PM, H. Peter Anvin wrote:
> On 07/15/2010 03:27 PM, Yinghai Lu wrote:
>>
>> to save the early_serial_base.
>>
>> Also bootloader could fill that field, so setup code could reuse it.
>>
>> decompress code could reuse early serial console from setup code.
>>
>> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
>>
> 
> What's the point with this over what we currently have?

extend serial console coverage to boot/compressed/misc.c

before this one, we have cover in boot/*.c only.

Thanks

Yinghai

Re: [PATCH] x86,setup: add serial_console_port_base in boot_params

[Cyrill Gorcunov]

On Thu, Jul 15, 2010 at 03:27:18PM -0700, Yinghai Lu wrote:
> 
> to save the early_serial_base.
> 
> Also bootloader could fill that field, so setup code could reuse it.
> 
> decompress code could reuse early serial console from setup code.
> 
> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
> 

Hi Yinghai, sorry for delayed response. I like the idea much since it'll allow
to log decompressor messages in case if someone would be changing exitsting code
or developing new one, though this touches boot protocol so that grub/syslinux
and friends will have to update their code as well which of course need some
time.

	-- Cyrill

Re: [PATCH] x86,setup: add serial_console_port_base in boot_params

[H. Peter Anvin]

On 07/31/2010 01:34 AM, Cyrill Gorcunov wrote:
> On Thu, Jul 15, 2010 at 03:27:18PM -0700, Yinghai Lu wrote:
>>
>> to save the early_serial_base.
>>
>> Also bootloader could fill that field, so setup code could reuse it.
>>
>> decompress code could reuse early serial console from setup code.
>>
>> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
>>
> 
> Hi Yinghai, sorry for delayed response. I like the idea much since it'll allow
> to log decompressor messages in case if someone would be changing exitsting code
> or developing new one, though this touches boot protocol so that grub/syslinux
> and friends will have to update their code as well which of course need some
> time.
> 

No, this is the internal part of the boot protocol, so it's not an issue.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

Re: [PATCH] x86,setup: add serial_console_port_base in boot_params

[Cyrill Gorcunov]

On Sat, Jul 31, 2010 at 11:21:35AM -0700, H. Peter Anvin wrote:
> On 07/31/2010 01:34 AM, Cyrill Gorcunov wrote:
> > On Thu, Jul 15, 2010 at 03:27:18PM -0700, Yinghai Lu wrote:
> >>
> >> to save the early_serial_base.
> >>
> >> Also bootloader could fill that field, so setup code could reuse it.
> >>
> >> decompress code could reuse early serial console from setup code.
> >>
> >> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
> >>
> > 
> > Hi Yinghai, sorry for delayed response. I like the idea much since it'll allow
> > to log decompressor messages in case if someone would be changing exitsting code
> > or developing new one, though this touches boot protocol so that grub/syslinux
> > and friends will have to update their code as well which of course need some
> > time.
> > 
> 
> No, this is the internal part of the boot protocol, so it's not an issue.
> 

Peter, I didn't mean any issue here, I meant that bootloaders don't know about
this field yet and they will have to update own sources to pass port value
at proper place of boot params. Or I miss something?

> 	-hpa
> 
	-- Cyrill

Re: [PATCH] x86,setup: add serial_console_port_base in boot_params

[H. Peter Anvin]

On 07/31/2010 11:32 AM, Cyrill Gorcunov wrote:
>>
>> No, this is the internal part of the boot protocol, so it's not an issue.
>>
> 
> Peter, I didn't mean any issue here, I meant that bootloaders don't know about
> this field yet and they will have to update own sources to pass port value
> at proper place of boot params. Or I miss something?
> 

Boot loaders that use the 16-bit entry point are unaffected.

Boot loaders which use the 32-bit entry point but properly clears the
zero page simply will not have the feature.

Boot loaders which use the 32-bit entry point but doesn't clear the zero
page are broken.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

Re: [PATCH] x86,setup: add serial_console_port_base in boot_params

[Cyrill Gorcunov]

On Sat, Jul 31, 2010 at 02:02:53PM -0700, H. Peter Anvin wrote:
> On 07/31/2010 11:32 AM, Cyrill Gorcunov wrote:
> >>
> >> No, this is the internal part of the boot protocol, so it's not an issue.
> >>
> > 
> > Peter, I didn't mean any issue here, I meant that bootloaders don't know about
> > this field yet and they will have to update own sources to pass port value
> > at proper place of boot params. Or I miss something?
> > 
> 
> Boot loaders that use the 16-bit entry point are unaffected.
> 
> Boot loaders which use the 32-bit entry point but properly clears the
> zero page simply will not have the feature.
> 
> Boot loaders which use the 32-bit entry point but doesn't clear the zero
> page are broken.
> 
> 	-hpa
>

Well, Peter, seems I messed boot params with setup header. So I don't see
any user of this field then, hmm...

	-- Cyrill

Re: [PATCH] x86,setup: add serial_console_port_base in boot_params

[Yinghai Lu]

On 07/31/2010 02:02 PM, H. Peter Anvin wrote:
> On 07/31/2010 11:32 AM, Cyrill Gorcunov wrote:
>>>
>>> No, this is the internal part of the boot protocol, so it's not an issue.
>>>
>>
>> Peter, I didn't mean any issue here, I meant that bootloaders don't know about
>> this field yet and they will have to update own sources to pass port value
>> at proper place of boot params. Or I miss something?
>>
> 
> Boot loaders that use the 16-bit entry point are unaffected.
> 
> Boot loaders which use the 32-bit entry point but properly clears the
> zero page simply will not have the feature.
> 
> Boot loaders which use the 32-bit entry point but doesn't clear the zero
> page are broken.
> 
can you if this one is right for kexec path?

Thanks

Yinghai

[PATCH] kexec-tools: pass serial console base for early console in kernel

when kexec is used with "console_serial", set serial_console_port_base in boot_params.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>

---
 doc/linux-i386-zero-page.txt      |    1 +
 include/x86/x86-linux.h           |    3 ++-
 kexec/arch/i386/kexec-x86.h       |    1 +
 kexec/arch/i386/x86-linux-setup.c |    4 ++++
 kexec/arch/x86_64/kexec-x86_64.c  |    9 +--------
 5 files changed, 9 insertions(+), 9 deletions(-)

Index: kexec-tools/doc/linux-i386-zero-page.txt
===================================================================
--- kexec-tools.orig/doc/linux-i386-zero-page.txt
+++ kexec-tools/doc/linux-i386-zero-page.txt
@@ -22,6 +22,7 @@ Offset	Type		Description
 			  0x90000 + contents of CL_OFFSET
 			(only taken, when CL_MAGIC = 0xA33F)
  0x40	20 bytes	struct apm_bios_info, APM_BIOS_INFO
+ 0x54   2 bytes		serial console base
  0x60	16 bytes	Intel SpeedStep (IST) BIOS support information
  0x80	16 bytes	hd0-disk-parameter from intvector 0x41
  0x90	16 bytes	hd1-disk-parameter from intvector 0x46
Index: kexec-tools/include/x86/x86-linux.h
===================================================================
--- kexec-tools.orig/include/x86/x86-linux.h
+++ kexec-tools/include/x86/x86-linux.h
@@ -40,7 +40,6 @@ struct apm_bios_info {
 	uint16_t cseg_len;	/* 0x4e */
 	uint16_t cseg_16_len;	/* 0x50 */
 	uint16_t dseg_len;	/* 0x52 */
-	uint8_t  reserved[44];	/* 0x54 */
 };
 
 /*
@@ -105,6 +104,8 @@ struct x86_linux_param_header {
 	uint8_t  reserved4[12];			/* 0x34 -- 0x3f reserved for future expansion */
 
 	struct apm_bios_info apm_bios_info;	/* 0x40 */
+	uint16_t  serial_console_port_base;	/* 0x54 */
+	uint8_t  reserved41[42];		/* 0x56 */
 	struct drive_info_struct drive_info;	/* 0x80 */
 	struct sys_desc_table sys_desc_table;	/* 0xa0 */
 	uint32_t alt_mem_k;			/* 0x1e0 */
Index: kexec-tools/kexec/arch/i386/x86-linux-setup.c
===================================================================
--- kexec-tools.orig/kexec/arch/i386/x86-linux-setup.c
+++ kexec-tools/kexec/arch/i386/x86-linux-setup.c
@@ -100,6 +100,9 @@ void setup_linux_bootloader_parameters(
 	cmdline_ptr = ((char *)real_mode) + cmdline_offset;
 	memcpy(cmdline_ptr, cmdline, cmdline_len);
 	cmdline_ptr[cmdline_len - 1] = '\0';
+
+	if (arch_options.console_serial)
+		real_mode->serial_console_port_base = arch_options.serial_base;
 }
 
 int setup_linux_vesafb(struct x86_linux_param_header *real_mode)
@@ -422,6 +425,7 @@ void setup_linux_system_parameters(struc
 
 	/* Default APM info */
 	memset(&real_mode->apm_bios_info, 0, sizeof(real_mode->apm_bios_info));
+
 	/* Default drive info */
 	memset(&real_mode->drive_info, 0, sizeof(real_mode->drive_info));
 	/* Default sysdesc table */
Index: kexec-tools/kexec/arch/i386/kexec-x86.h
===================================================================
--- kexec-tools.orig/kexec/arch/i386/kexec-x86.h
+++ kexec-tools/kexec/arch/i386/kexec-x86.h
@@ -51,6 +51,7 @@ struct arch_options_t {
 	uint8_t  	console_serial;
 	enum coretype	core_header_type;
 };
+extern struct arch_options_t arch_options;
 
 int multiboot_x86_probe(const char *buf, off_t len);
 int multiboot_x86_load(int argc, char **argv, const char *buf, off_t len,
Index: kexec-tools/kexec/arch/x86_64/kexec-x86_64.c
===================================================================
--- kexec-tools.orig/kexec/arch/x86_64/kexec-x86_64.c
+++ kexec-tools/kexec/arch/x86_64/kexec-x86_64.c
@@ -55,14 +55,7 @@ void arch_usage(void)
 		);
 }
 
-static struct {
-	uint8_t  reset_vga;
-	uint16_t serial_base;
-	uint32_t serial_baud;
-	uint8_t  console_vga;
-	uint8_t  console_serial;
-	int core_header_type;
-} arch_options = {
+struct arch_options_t arch_options = {
 	.reset_vga   = 0,
 	.serial_base = 0x3f8,
 	.serial_baud = 0,

Re: [PATCH] x86,setup: add serial_console_port_base in boot_params

[Eric W. Biederman]

Yinghai Lu <yinghai@kernel.org> writes:

> On 07/31/2010 02:02 PM, H. Peter Anvin wrote:
>> On 07/31/2010 11:32 AM, Cyrill Gorcunov wrote:
>>>>
>>>> No, this is the internal part of the boot protocol, so it's not an issue.
>>>>
>>>
>>> Peter, I didn't mean any issue here, I meant that bootloaders don't know about
>>> this field yet and they will have to update own sources to pass port value
>>> at proper place of boot params. Or I miss something?
>>>
>> 
>> Boot loaders that use the 16-bit entry point are unaffected.
>> 
>> Boot loaders which use the 32-bit entry point but properly clears the
>> zero page simply will not have the feature.
>> 
>> Boot loaders which use the 32-bit entry point but doesn't clear the zero
>> page are broken.
>> 
> can you if this one is right for kexec path?

I am walking out the door, but this seems like nonsense to me.

The kexec console_serial option today is a debugging feature for
when you to debug the purgatory code.  Only once in a bluemoon
should it be useful, so I don't see why we would add it here.
The kexec purgatory is silent by default.

Further I don't see why we would add something to the zero page
when we have a perfectly good way to pass this information via
the kernel command line.  strstr and strtoul are trivial little
functions so I don't see why anything would need to parse anything
other than console= or early_printk=.  The difference in code size
is negligible.

This option in the zero page appears very fragile. There are a lot of
dimensions that we are skipping.  I admit we can detect most of them
by reading the serial port.  But we still have the assumption that the
serial port is an 8259 serial port in i/o space and not mmio space.

*runs out the door before another silly email comes*

Eric
>
> [PATCH] kexec-tools: pass serial console base for early console in kernel
>
> when kexec is used with "console_serial", set serial_console_port_base in boot_params.
>
> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
>
> ---
>  doc/linux-i386-zero-page.txt      |    1 +
>  include/x86/x86-linux.h           |    3 ++-
>  kexec/arch/i386/kexec-x86.h       |    1 +
>  kexec/arch/i386/x86-linux-setup.c |    4 ++++
>  kexec/arch/x86_64/kexec-x86_64.c  |    9 +--------
>  5 files changed, 9 insertions(+), 9 deletions(-)
>
> Index: kexec-tools/doc/linux-i386-zero-page.txt
> ===================================================================
> --- kexec-tools.orig/doc/linux-i386-zero-page.txt
> +++ kexec-tools/doc/linux-i386-zero-page.txt
> @@ -22,6 +22,7 @@ Offset	Type		Description
>  			  0x90000 + contents of CL_OFFSET
>  			(only taken, when CL_MAGIC = 0xA33F)
>   0x40	20 bytes	struct apm_bios_info, APM_BIOS_INFO
> + 0x54   2 bytes		serial console base
>   0x60	16 bytes	Intel SpeedStep (IST) BIOS support information
>   0x80	16 bytes	hd0-disk-parameter from intvector 0x41
>   0x90	16 bytes	hd1-disk-parameter from intvector 0x46
> Index: kexec-tools/include/x86/x86-linux.h
> ===================================================================
> --- kexec-tools.orig/include/x86/x86-linux.h
> +++ kexec-tools/include/x86/x86-linux.h
> @@ -40,7 +40,6 @@ struct apm_bios_info {
>  	uint16_t cseg_len;	/* 0x4e */
>  	uint16_t cseg_16_len;	/* 0x50 */
>  	uint16_t dseg_len;	/* 0x52 */
> -	uint8_t  reserved[44];	/* 0x54 */
>  };
>  
>  /*
> @@ -105,6 +104,8 @@ struct x86_linux_param_header {
>  	uint8_t  reserved4[12];			/* 0x34 -- 0x3f reserved for future expansion */
>  
>  	struct apm_bios_info apm_bios_info;	/* 0x40 */
> +	uint16_t  serial_console_port_base;	/* 0x54 */
> +	uint8_t  reserved41[42];		/* 0x56 */
>  	struct drive_info_struct drive_info;	/* 0x80 */
>  	struct sys_desc_table sys_desc_table;	/* 0xa0 */
>  	uint32_t alt_mem_k;			/* 0x1e0 */
> Index: kexec-tools/kexec/arch/i386/x86-linux-setup.c
> ===================================================================
> --- kexec-tools.orig/kexec/arch/i386/x86-linux-setup.c
> +++ kexec-tools/kexec/arch/i386/x86-linux-setup.c
> @@ -100,6 +100,9 @@ void setup_linux_bootloader_parameters(
>  	cmdline_ptr = ((char *)real_mode) + cmdline_offset;
>  	memcpy(cmdline_ptr, cmdline, cmdline_len);
>  	cmdline_ptr[cmdline_len - 1] = '\0';
> +
> +	if (arch_options.console_serial)
> +		real_mode->serial_console_port_base = arch_options.serial_base;
>  }
>  
>  int setup_linux_vesafb(struct x86_linux_param_header *real_mode)
> @@ -422,6 +425,7 @@ void setup_linux_system_parameters(struc
>  
>  	/* Default APM info */
>  	memset(&real_mode->apm_bios_info, 0, sizeof(real_mode->apm_bios_info));
> +
>  	/* Default drive info */
>  	memset(&real_mode->drive_info, 0, sizeof(real_mode->drive_info));
>  	/* Default sysdesc table */
> Index: kexec-tools/kexec/arch/i386/kexec-x86.h
> ===================================================================
> --- kexec-tools.orig/kexec/arch/i386/kexec-x86.h
> +++ kexec-tools/kexec/arch/i386/kexec-x86.h
> @@ -51,6 +51,7 @@ struct arch_options_t {
>  	uint8_t  	console_serial;
>  	enum coretype	core_header_type;
>  };
> +extern struct arch_options_t arch_options;
>  
>  int multiboot_x86_probe(const char *buf, off_t len);
>  int multiboot_x86_load(int argc, char **argv, const char *buf, off_t len,
> Index: kexec-tools/kexec/arch/x86_64/kexec-x86_64.c
> ===================================================================
> --- kexec-tools.orig/kexec/arch/x86_64/kexec-x86_64.c
> +++ kexec-tools/kexec/arch/x86_64/kexec-x86_64.c
> @@ -55,14 +55,7 @@ void arch_usage(void)
>  		);
>  }
>  
> -static struct {
> -	uint8_t  reset_vga;
> -	uint16_t serial_base;
> -	uint32_t serial_baud;
> -	uint8_t  console_vga;
> -	uint8_t  console_serial;
> -	int core_header_type;
> -} arch_options = {
> +struct arch_options_t arch_options = {
>  	.reset_vga   = 0,
>  	.serial_base = 0x3f8,
>  	.serial_baud = 0,

Re: [PATCH] x86,setup: add serial_console_port_base in boot_params

[Yinghai Lu]

On 07/31/2010 07:42 PM, Eric W. Biederman wrote:
> Yinghai Lu <yinghai@kernel.org> writes:
> 
>> On 07/31/2010 02:02 PM, H. Peter Anvin wrote:
>>> On 07/31/2010 11:32 AM, Cyrill Gorcunov wrote:
>>>>>
>>>>> No, this is the internal part of the boot protocol, so it's not an issue.
>>>>>
>>>>
>>>> Peter, I didn't mean any issue here, I meant that bootloaders don't know about
>>>> this field yet and they will have to update own sources to pass port value
>>>> at proper place of boot params. Or I miss something?
>>>>
>>>
>>> Boot loaders that use the 16-bit entry point are unaffected.
>>>
>>> Boot loaders which use the 32-bit entry point but properly clears the
>>> zero page simply will not have the feature.
>>>
>>> Boot loaders which use the 32-bit entry point but doesn't clear the zero
>>> page are broken.
>>>
>> can you if this one is right for kexec path?
> 
> I am walking out the door, but this seems like nonsense to me.
> 
> Further I don't see why we would add something to the zero page
> when we have a perfectly good way to pass this information via
> the kernel command line.  strstr and strtoul are trivial little
> functions so I don't see why anything would need to parse anything
> other than console= or early_printk=.  The difference in code size
> is negligible.
> 
so you prefer to check command line for console info in arch/x86/boot/compressed/misc.c again?

that commandline is analyzed in arch/x86/boot/tty.c already.

Yinghai

Re: [PATCH] x86,setup: add serial_console_port_base in boot_params

[Eric W. Biederman]

Yinghai Lu <yinghai@kernel.org> writes:

> On 07/31/2010 07:42 PM, Eric W. Biederman wrote:
>> Yinghai Lu <yinghai@kernel.org> writes:
>> 
>>> On 07/31/2010 02:02 PM, H. Peter Anvin wrote:
>>>> On 07/31/2010 11:32 AM, Cyrill Gorcunov wrote:
>>>>>>
>>>>>> No, this is the internal part of the boot protocol, so it's not an issue.
>>>>>>
>>>>>
>>>>> Peter, I didn't mean any issue here, I meant that bootloaders don't know about
>>>>> this field yet and they will have to update own sources to pass port value
>>>>> at proper place of boot params. Or I miss something?
>>>>>
>>>>
>>>> Boot loaders that use the 16-bit entry point are unaffected.
>>>>
>>>> Boot loaders which use the 32-bit entry point but properly clears the
>>>> zero page simply will not have the feature.
>>>>
>>>> Boot loaders which use the 32-bit entry point but doesn't clear the zero
>>>> page are broken.
>>>>
>>> can you if this one is right for kexec path?
>> 
>> I am walking out the door, but this seems like nonsense to me.
>> 
>> Further I don't see why we would add something to the zero page
>> when we have a perfectly good way to pass this information via
>> the kernel command line.  strstr and strtoul are trivial little
>> functions so I don't see why anything would need to parse anything
>> other than console= or early_printk=.  The difference in code size
>> is negligible.
>> 
> so you prefer to check command line for console info in arch/x86/boot/compressed/misc.c again?
>
> that commandline is analyzed in arch/x86/boot/tty.c already.

Instead of changing 2 or 3 bootloaders, waiting years for the change
to propagate, and then trying to change users habits.

I definitely do.

Eric