x86/acpi, x86/boot: Take RSDP address from boot params if available

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" <hpa@zytor.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
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 <mingo@kernel.org>

diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h
index a06cbf0..60733f1 100644 (file)
--- a/arch/x86/include/uapi/asm/bootparam.h
+++ b/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 */

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index fb3b1f3..06635fb 100644 (file)
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -1776,5 +1776,5 @@ void __init arch_reserve_mem_area(acpi_physical_address addr, size_t size)
 
 u64 x86_default_get_root_pointer(void)
 {
-       return 0;
+       return boot_params.acpi_rsdp_addr;
 }