Re: [PATCH v2] kdump: pass acpi_rsdp= to 2nd kernel for efi booting

Eric W. Biederman
2012-10-18T21:21:56Z

Dave Young <dyoung@redhat.com> writes:

> In case efi booting, kdump need kernel parameter acpi_rsdp= to retrieve
> the acpi root table physical address.
>
> Add a function cmdline_add_efi to get the address from /sys/firmware/efi/systab
> If there's no such file or read fail the function will just do nothing.
>
> Tested efi boot Fedora 17 on thinkpad T420.
>
> Some background info for this issue:
> http://lists.infradead.org/pipermail/kexec/2010-March/003889.html
>
> [v1 -> v2]:
> Address comments from Khalid and Simon
> use fgets instead of read(2) to iterate the file
> do not add 'noefi' because kexec does not construct EFI signature
> in bootloader signature in boot_params, so kexec'd kernel will
> disable EFI automatically even without noefi.

I don't have any problems with this patch.

I have a question. In the case where this fails are we successfully
passing the ACPI sections in the e820 map?

If we are passing the acpi sections is that not enough for the kernel
to find the rdsp area? I'm just a bit surprised we need this patch
is all.

Somehow it seems a bit ugly to pass information that could be conveyed
in the memory map on the command line.

But I am all in favor of doing what works.

Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>

> Signed-off-by: Dave Young <dyoung@redhat.com>
> ---
> kexec/arch/i386/crashdump-x86.c | 35 +++++++++++++++++++++++++++++++++++
> 1 file changed, 35 insertions(+)
>
> --- kexec-tools.orig/kexec/arch/i386/crashdump-x86.c
> +++ kexec-tools/kexec/arch/i386/crashdump-x86.c
> @@ -835,6 +835,40 @@ static int cmdline_add_memmap_acpi(char
> return 0;
> }
>
> +/* Appends 'acpi_rsdp=' commandline for efi boot crash dump */
> +static void cmdline_add_efi(char *cmdline)
> +{
> + FILE *fp;
> + int cmdlen, len;
> + char line[MAX_LINE], *s;
> + const char *acpis = " acpi_rsdp=";
> +
> + fp = fopen("/sys/firmware/efi/systab", "r");
> + if (!fp)
> + return;
> +
> + while(fgets(line, sizeof(line), fp) != 0) {
> + /* ACPI20= always goes before ACPI= */
> + if ((strstr(line, "ACPI20=")) || (strstr(line, "ACPI="))) {
> + line[strlen(line) - 1] = '\0';
> + s = strchr(line, '=');
> + s += 1;
> + len = strlen(s) + strlen(acpis);
> + cmdlen = strlen(cmdline) + len;
> + if (cmdlen > (COMMAND_LINE_SIZE - 1))
> + die("Command line overflow\n");
> + strcat(cmdline, acpis);
> + strcat(cmdline, s);
> + dbgprintf("Command line after adding efi\n");
> + dbgprintf("%s\n", cmdline);
> +
> + break;
> + }
> + }
> +
> + fclose(fp);
> +}
> +
> static void get_backup_area(struct kexec_info *info,
> struct memory_range *range, int ranges)
> {
> @@ -998,6 +1032,7 @@ int load_crashdump_segments(struct kexec
> if (delete_memmap(memmap_p, elfcorehdr, memsz) < 0)
> return -1;
> cmdline_add_memmap(mod_cmdline, memmap_p);
> + cmdline_add_efi(mod_cmdline);
> cmdline_add_elfcorehdr(mod_cmdline, elfcorehdr);
>
> /* Inform second kernel about the presence of ACPI tables. */
>
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