[PATCH] x86: Always to to fill acpi_rsdp_addr in boot params

Kairui Song kasong at redhat.com
Thu Apr 4 11:05:33 PDT 2019

On Thu, Apr 4, 2019 at 3:25 PM Dave Young <dyoung at redhat.com> wrote:
> Hello Kairui
> On 03/28/19 at 05:49pm, Kairui Song wrote:
> > Since kernel commit e6e094e053af75 ("x86/acpi, x86/boot: Take RSDP address
> > from boot params if available"), kernel accept a acpi_rsdp_addr param in
> > boot_params. Sync the x86_linux_param_header to support this param.
> >
> > And previously we are already appending 'acpi_rsdp=' command line only for
> > loading crash kernel on EFI systems, it will be better to try to set the
> > boot param for any kernel get loaded, to help the kernel finding the
> > RSDP value more stably. Otherwise if the user decide to disable EFI
> > service in second kernel, it will fail to boot.
> >
> > There is no better way to find the RSDP address from legacy BIOS
> > interface rather than scanning the memory region and search for it,
> > which will always be done by the kernel as a fallback, so we only
> > look for RSDP in previous boot params, cmdline and EFI firmware.
> It would be good to always pass acpi_rsdp= kernel cmdline in case
> efi=old_map.  (or maybe efi=noruntime as well, but I did not remember
> the behavior of noruntime now), no matter kexec or kdump..
> And if you want, maybe fill the boot_params instead of passing cmdline
> for new kernel which supports the new boot_param field.
> Split the patch to small patches would be better.
> Thanks
> Dave

Thanks for the review!

I'll update in V2 accordingly.

Best Regards,
Kairui Song

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