efi: Add a function to look up existing IO memory mappings

The EFI initialization creates virtual mappings for EFI boot services memory, so if a driver wants to access EFI boot services memory, it cannot call ioremap itself; doing so will trip the WARN about mapping RAM twice. Thus, a driver accessing EFI boot services memory must do so via the existing mapping already created during EFI intiialization. Since the EFI code already maintains a memory map for that memory, add a function efi_lookup_mapped_addr to look up mappings in that memory map. Signed-off-by: Josh Triplett <[email protected]> Link: http://lkml.kernel.org/r/0eb48ae012797912874919110660ad420b90268b.1348876882.git.josh@joshtriplett.org Signed-off-by: H. Peter Anvin <[email protected]>
kcc · Sep 29, 2012 · 7bc90e0 · 7bc90e0
1 parent 7851079
commit 7bc90e0
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diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
@@ -776,6 +776,34 @@ static void __init runtime_code_page_mkexec(void)
 	}
 }
 
+/*
+ * We can't ioremap data in EFI boot services RAM, because we've already mapped
+ * it as RAM.  So, look it up in the existing EFI memory map instead.  Only
+ * callable after efi_enter_virtual_mode and before efi_free_boot_services.
+ */
+void __iomem *efi_lookup_mapped_addr(u64 phys_addr)
+{
+	void *p;
+	if (WARN_ON(!memmap.map))
+		return NULL;
+	for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) {
+		efi_memory_desc_t *md = p;
+		u64 size = md->num_pages << EFI_PAGE_SHIFT;
+		u64 end = md->phys_addr + size;
+		if (!(md->attribute & EFI_MEMORY_RUNTIME) &&
+		    md->type != EFI_BOOT_SERVICES_CODE &&
+		    md->type != EFI_BOOT_SERVICES_DATA)
+			continue;
+		if (!md->virt_addr)
+			continue;
+		if (phys_addr >= md->phys_addr && phys_addr < end) {
+			phys_addr += md->virt_addr - md->phys_addr;
+			return (__force void __iomem *)(unsigned long)phys_addr;
+		}
+	}
+	return NULL;
+}
+
 /*
  * This function will switch the EFI runtime services to virtual mode.
  * Essentially, look through the EFI memmap and map every region that

diff --git a/include/linux/efi.h b/include/linux/efi.h
@@ -501,6 +501,7 @@ extern void efi_free_boot_services(void);
 #else
 static inline void efi_free_boot_services(void) {}
 #endif
+extern void __iomem *efi_lookup_mapped_addr(u64 phys_addr);
 extern u64 efi_get_iobase (void);
 extern u32 efi_mem_type (unsigned long phys_addr);
 extern u64 efi_mem_attributes (unsigned long phys_addr);