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Date: Sat, 31 Jul 2010 19:42:14 -0700
From: ebiederm@...ssion.com (Eric W. Biederman)
To: Yinghai Lu <yinghai@...nel.org>
Cc: "H. Peter Anvin" <hpa@...or.com>,
Cyrill Gorcunov <gorcunov@...il.com>,
Ingo Molnar <mingo@...e.hu>,
Thomas Gleixner <tglx@...utronix.de>,
Pekka Enberg <penberg@...helsinki.fi>,
"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
kexec@...ts.infradead.org
Subject: Re: [PATCH] x86,setup: add serial_console_port_base in boot_params
Yinghai Lu <yinghai@...nel.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@...nel.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,
--
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