linux-kernel - [PATCH 2/2] x86/acpi, x86/boot: Take RSDP address from boot params if available

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Date:   Tue, 20 Nov 2018 08:22:45 +0100
From:   Juergen Gross <jgross@...e.com>
To:     linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
        x86@...nel.org
Cc:     boris.ostrovsky@...cle.com, sstabellini@...nel.org, hpa@...or.com,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dkiper@...cle.com, Juergen Gross <jgross@...e.com>
Subject: [PATCH 2/2] 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.

Signed-off-by: Juergen Gross <jgross@...e.com>
---
 arch/x86/include/uapi/asm/bootparam.h | 3 ++-
 arch/x86/kernel/acpi/boot.c           | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h
index a06cbf019744..60733f137e9a 100644
--- 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 fb3b1f3a5aba..06635fbca81c 100644
--- 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;
 }
-- 
2.16.4