Re: [PATCH] x86/kexec: Copy ACPI root pointer address from config table

[Richard Lyu <richard.lyu@suse.com>]

On 2026/02/17 17:35, Ard Biesheuvel wrote:
>Dave reports that kexec may fail when the first kernel boots via the EFI
>stub but without EFI runtime services, as in that case, the RSDP address
>field in struct bootparams is never assigned. Kexec copies this value
>into the version of struct bootparams that it provides to the incoming
>kernel, which may have no other means to locate the ACPI root pointer.
>
>So take the value from the EFI config tables if no root pointer has been
>set in the first kernel's struct bootparams.
>
>Fixes: a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")
>Cc: <stable@vger.kernel.org> # v6.1
>Reported-by: Dave Young <dyoung@redhat.com>
>Tested-by: Dave Young <dyoung@redhat.com>
>Link: https://lore.kernel.org/linux-efi/aZQg_tRQmdKNadCg@darkstar.users.ipa.redhat.com/
>Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
>---
>Unless anyone minds, I intend to take this via the EFI tree as a fix.
>
> arch/x86/kernel/kexec-bzimage64.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
>diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
>index 7508d0ccc740..24aec7c1153f 100644
>--- a/arch/x86/kernel/kexec-bzimage64.c
>+++ b/arch/x86/kernel/kexec-bzimage64.c
>@@ -313,6 +313,12 @@ setup_boot_parameters(struct kimage *image, struct boot_params *params,
>
> 	/* Always fill in RSDP: it is either 0 or a valid value */
> 	params->acpi_rsdp_addr = boot_params.acpi_rsdp_addr;
>+	if (IS_ENABLED(CONFIG_EFI) && !params->acpi_rsdp_addr) {
>+		if (efi.acpi20 != EFI_INVALID_TABLE_ADDR)
>+			params->acpi_rsdp_addr = efi.acpi20;
>+		else if (efi.acpi != EFI_INVALID_TABLE_ADDR)
>+			params->acpi_rsdp_addr = efi.acpi;
>+	}
>
> 	/* Default APM info */
> 	memset(&params->apm_bios_info, 0, sizeof(params->apm_bios_info));
>-- 2.53.0.273.g2a3d683680-goog

This change is good to me.

Reviewed-by: Richard Lyu <richard.lyu@suse.com>