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SubjectRe: [PATCH v4] x86/boot: Use efi_setup_data for searching RSDP on kexec-ed kernel
On 04/11/19 at 08:16am, Junichi Nomura wrote:
> On 4/11/19 5:09 PM, Borislav Petkov wrote:
> > On Wed, Apr 10, 2019 at 11:34:51PM +0000, Junichi Nomura wrote:
> >> But efi_get_rsdp_addr() needs to check whether the kernel was
> >> kexec booted to avoid accessing invalid EFI table address.
> >> efi_get_kexec_setup_data_addr() is the only method I know
> >> to check if it was kexec-booted.
> >
> > Your v3 had the right approach - you first check if you can get the
> > address as a kexec-ed kernel. If you do, you use that one and continue
> > the normal path.
> >
> > If you don't, you fall back to efi_get_rsdp_addr() and get it directly
> > from EFI.
> >
> > And then carve out the functionality you need to call multiple times in
> > helper functions like __efi_get_rsdp_addr().
> >
> > Why doesn't that work anymore?
> kexec_get_rsdp_addr() might fail on kexec-booted kernel, e.g. if the
> setup_data was invalid. In such a case, falling back to efi_get_rsdp_addr()
> will hit the problem of accessing invalid table pointer again.

Seems you are trying to address Dave Young's comment in

We may need discuss and make clear if those are doable. E.g the first
comment, if not hang by below line of code, returning 0 for what? Can
kexec still be saved, or just reset to firmware?

error("EFI system table not found in kexec boot_params.")

It may need be clarified firstly, then go further to rearrange patch.
That can ease the work, I guess.

Personal opinion.


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