[PATCH] Remove warning in efi_enter_virtual_mode

[Bryan O'Donoghue]

This warning is caused by efi_enter_virtual_mode mapping memory marked
as !EFI_RUNTIME_MEMORY. The reason this memory is being mapped is to
work around buggy code that stores an ACPI object called the Boot
Graphics Resource Table - BGRT in memory of type EfiBootServices*.

------------[ cut here ]------------
WARNING: at arch/x86/mm/ioremap.c:102 __ioremap_caller+0x3d3/0x440()
Modules linked in:
Pid: 0, comm: swapper Not tainted 3.9.0-rc7+ #95
Call Trace:
 [<c102b6af>] warn_slowpath_common+0x5f/0x80
 [<c1023fb3>] ? __ioremap_caller+0x3d3/0x440
 [<c1023fb3>] ? __ioremap_caller+0x3d3/0x440
 [<c102b6ed>] warn_slowpath_null+0x1d/0x20
 [<c1023fb3>] __ioremap_caller+0x3d3/0x440
 [<c106007b>] ? get_usage_chars+0xfb/0x110
 [<c102d937>] ? vprintk_emit+0x147/0x480
 [<c1418593>] ? efi_enter_virtual_mode+0x1e4/0x3de
 [<c102406a>] ioremap_cache+0x1a/0x20
 [<c1418593>] ? efi_enter_virtual_mode+0x1e4/0x3de
 [<c1418593>] efi_enter_virtual_mode+0x1e4/0x3de
 [<c1407984>] start_kernel+0x286/0x2f4
 [<c1407535>] ? repair_env_string+0x51/0x51
 [<c1407362>] i386_start_kernel+0x12c/0x12f
---[ end trace 4eaa2a86a8e2da22 ]---

On systems that do not have a BGRT object, there's no reason to map this
memory in efi_enter_virtual_mode. This patch searches for the BGRT
object and if found - will continue to map the boot services memory,
else only memory with attribute EFI_RUNTIME_MEMORY will be mapped.

Mapping only memory EFI_RUNTIME_MEMORY is is consistent with the code in
arch/ia64/kernel/efi.c:efi_enter_virtual_mode();

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue.lkml@xxxxxxxxxxxxxxxxx>
---
 arch/x86/platform/efi/efi-bgrt.c |   20 +++++++++++++++-----
 arch/x86/platform/efi/efi.c      |   12 +++++++++---
 include/linux/efi-bgrt.h         |    2 ++
 3 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/arch/x86/platform/efi/efi-bgrt.c b/arch/x86/platform/efi/efi-bgrt.c
index 7145ec6..3655d62 100644
--- a/arch/x86/platform/efi/efi-bgrt.c
+++ b/arch/x86/platform/efi/efi-bgrt.c
@@ -25,19 +25,29 @@ struct bmp_header {
 	u32 size;
 } __packed;
 
-void __init efi_bgrt_init(void)
+bool __init efi_bgrt_probe(void)
 {
 	acpi_status status;
-	void __iomem *image;
-	bool ioremapped = false;
-	struct bmp_header bmp_header;
 
 	if (acpi_disabled)
-		return;
+		return false;
 
+	bgrt_tab = NULL;
 	status = acpi_get_table("BGRT", 0,
 	                        (struct acpi_table_header **)&bgrt_tab);
 	if (ACPI_FAILURE(status))
+		return false;
+
+	return true;
+}
+
+void __init efi_bgrt_init(void)
+{
+	void __iomem *image;
+	bool ioremapped = false;
+	struct bmp_header bmp_header;
+
+	if (acpi_disabled || bgrt_tab == NULL)
 		return;
 
 	if (bgrt_tab->header.length < sizeof(*bgrt_tab))
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 5f2ecaf..7c64a2f 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -842,6 +842,7 @@ void __init efi_enter_virtual_mode(void)
 	u64 end, systab, start_pfn, end_pfn;
 	void *p, *va, *new_memmap = NULL;
 	int count = 0;
+	bool bgrt_map;
 
 	efi.systab = NULL;
 
@@ -855,6 +856,11 @@ void __init efi_enter_virtual_mode(void)
 		return;
 	}
 
+	/*
+	 * Determine if mapping EFI boot code/data is required for BGRT mapping
+	 */
+	bgrt_map = efi_bgrt_probe();
+
 	/* Merge contiguous regions of the same type and attribute */
 	for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) {
 		u64 prev_size;
@@ -884,9 +890,9 @@ void __init efi_enter_virtual_mode(void)
 
 	for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) {
 		md = p;
-		if (!(md->attribute & EFI_MEMORY_RUNTIME) &&
-		    md->type != EFI_BOOT_SERVICES_CODE &&
-		    md->type != EFI_BOOT_SERVICES_DATA)
+		if (!((md->attribute & EFI_MEMORY_RUNTIME) || (bgrt_map &&
+			(md->type == EFI_BOOT_SERVICES_CODE ||
+			 md->type == EFI_BOOT_SERVICES_DATA))))
 			continue;
 
 		size = md->num_pages << EFI_PAGE_SHIFT;
diff --git a/include/linux/efi-bgrt.h b/include/linux/efi-bgrt.h
index 051b21f..165426b 100644
--- a/include/linux/efi-bgrt.h
+++ b/include/linux/efi-bgrt.h
@@ -6,6 +6,7 @@
 #include <linux/acpi.h>
 
 void efi_bgrt_init(void);
+bool efi_bgrt_probe(void);
 
 /* The BGRT data itself; only valid if bgrt_image != NULL. */
 extern void *bgrt_image;
@@ -15,6 +16,7 @@ extern struct acpi_table_bgrt *bgrt_tab;
 #else /* !CONFIG_ACPI_BGRT */
 
 static inline void efi_bgrt_init(void) {}
+static inline bool efi_bgrt_probe(void) { return false; }
 
 #endif /* !CONFIG_ACPI_BGRT */
 
-- 
1.7.10.4

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