From: Juergen Gross Date: Tue, 20 Nov 2018 08:25:29 +0100 Subject: x86/acpi, x86/boot: Take RSDP address from boot params if available Origin: https://git.kernel.org/linus/e6e094e053af75cbc164e950814d3d084fb1e698 In case the RSDP address in struct boot_params is specified don't try to find the table by searching, but take the address directly as set by the boot loader. Suggested-by: "H. Peter Anvin" Signed-off-by: Juergen Gross Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: boris.ostrovsky@oracle.com Cc: bp@alien8.de Cc: daniel.kiper@oracle.com Cc: sstabellini@kernel.org Cc: xen-devel@lists.xenproject.org Link: http://lkml.kernel.org/r/20181120072529.5489-3-jgross@suse.com Signed-off-by: Ingo Molnar --- arch/x86/include/uapi/asm/bootparam.h | 3 ++- arch/x86/kernel/acpi/boot.c | 2 +- 2 files changed, 3 insertions(+), 2 deletions(-) Index: linux/arch/x86/include/uapi/asm/bootparam.h =================================================================== --- linux.orig/arch/x86/include/uapi/asm/bootparam.h +++ linux/arch/x86/include/uapi/asm/bootparam.h @@ -155,7 +155,8 @@ struct boot_params { __u8 _pad2[4]; /* 0x054 */ __u64 tboot_addr; /* 0x058 */ struct ist_info ist_info; /* 0x060 */ - __u8 _pad3[16]; /* 0x070 */ + __u64 acpi_rsdp_addr; /* 0x070 */ + __u8 _pad3[8]; /* 0x078 */ __u8 hd0_info[16]; /* obsolete! */ /* 0x080 */ __u8 hd1_info[16]; /* obsolete! */ /* 0x090 */ struct sys_desc_table sys_desc_table; /* obsolete! */ /* 0x0a0 */ Index: linux/arch/x86/kernel/acpi/boot.c =================================================================== --- linux.orig/arch/x86/kernel/acpi/boot.c +++ linux/arch/x86/kernel/acpi/boot.c @@ -1775,5 +1775,5 @@ void __init arch_reserve_mem_area(acpi_p u64 x86_default_get_root_pointer(void) { - return 0; + return boot_params.acpi_rsdp_addr; }