x86/efi: Add efi_fake_mem support for EFI_MEMORY_SP

Given that EFI_MEMORY_SP is platform BIOS policy decision for marking
memory ranges as "reserved for a specific purpose" there will inevitably
be scenarios where the BIOS omits the attribute in situations where it
is desired. Unlike other attributes if the OS wants to reserve this
memory from the kernel the reservation needs to happen early in init. So
early, in fact, that it needs to happen before e820__memblock_setup()
which is a pre-requisite for efi_fake_memmap() that wants to allocate
memory for the updated table.

Introduce an x86 specific efi_fake_memmap_early() that can search for
attempts to set EFI_MEMORY_SP via efi_fake_mem and update the e820 table
accordingly.

The KASLR code that scans the command line looking for user-directed
memory reservations also needs to be updated to consider
"efi_fake_mem=nn@ss:0x40000" requests.

Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

3 files changed, 45 insertions, 7 deletions

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index ff6fa81949cd..da0eedd5635d 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -132,8 +132,14 @@ char *skip_spaces(const char *str)
 #include "../../../../lib/ctype.c"
 #include "../../../../lib/cmdline.c"
 
+enum parse_mode {
+	PARSE_MEMMAP,
+	PARSE_EFI,
+};
+
 static int
-parse_memmap(char *p, unsigned long long *start, unsigned long long *size)
+parse_memmap(char *p, unsigned long long *start, unsigned long long *size,
+		enum parse_mode mode)
 {
 	char *oldp;
 
@@ -156,8 +162,29 @@ parse_memmap(char *p, unsigned long long *start, unsigned long long *size)
 		*start = memparse(p + 1, &p);
 		return 0;
 	case '@':
-		/* memmap=nn@ss specifies usable region, should be skipped */
-		*size = 0;
+		if (mode == PARSE_MEMMAP) {
+			/*
+			 * memmap=nn@ss specifies usable region, should
+			 * be skipped
+			 */
+			*size = 0;
+		} else {
+			unsigned long long flags;
+
+			/*
+			 * efi_fake_mem=nn@ss:attr the attr specifies
+			 * flags that might imply a soft-reservation.
+			 */
+			*start = memparse(p + 1, &p);
+			if (p && *p == ':') {
+				p++;
+				if (kstrtoull(p, 0, &flags) < 0)
+					*size = 0;
+				else if (flags & EFI_MEMORY_SP)
+					return 0;
+			}
+			*size = 0;
+		}
 		/* Fall through */
 	default:
 		/*
@@ -172,7 +199,7 @@ parse_memmap(char *p, unsigned long long *start, unsigned long long *size)
 	return -EINVAL;
 }
 
-static void mem_avoid_memmap(char *str)
+static void mem_avoid_memmap(enum parse_mode mode, char *str)
 {
 	static int i;
 
@@ -187,7 +214,7 @@ static void mem_avoid_memmap(char *str)
 		if (k)
 			*k++ = 0;
 
-		rc = parse_memmap(str, &start, &size);
+		rc = parse_memmap(str, &start, &size, mode);
 		if (rc < 0)
 			break;
 		str = k;
@@ -238,7 +265,6 @@ static void parse_gb_huge_pages(char *param, char *val)
 	}
 }
 
-
 static void handle_mem_options(void)
 {
 	char *args = (char *)get_cmd_line_ptr();
@@ -271,7 +297,7 @@ static void handle_mem_options(void)
 		}
 
 		if (!strcmp(param, "memmap")) {
-			mem_avoid_memmap(val);
+			mem_avoid_memmap(PARSE_MEMMAP, val);
 		} else if (strstr(param, "hugepages")) {
 			parse_gb_huge_pages(param, val);
 		} else if (!strcmp(param, "mem")) {
@@ -284,6 +310,8 @@ static void handle_mem_options(void)
 				goto out;
 
 			mem_limit = mem_size;
+		} else if (!strcmp(param, "efi_fake_mem")) {
+			mem_avoid_memmap(PARSE_EFI, val);
 		}
 	}
 
diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index 45f853bce869..d028e9acdf1c 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -263,4 +263,12 @@ static inline void efi_reserve_boot_services(void)
 }
 #endif /* CONFIG_EFI */
 
+#ifdef CONFIG_EFI_FAKE_MEMMAP
+extern void __init efi_fake_memmap_early(void);
+#else
+static inline void efi_fake_memmap_early(void)
+{
+}
+#endif
+
 #endif /* _ASM_X86_EFI_H */
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 8609dccea096..38d44f36d5ed 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -262,6 +262,8 @@ int __init efi_memblock_x86_reserve_range(void)
 	if (add_efi_memmap || do_efi_soft_reserve())
 		do_add_efi_memmap();
 
+	efi_fake_memmap_early();
+
 	WARN(efi.memmap.desc_version != 1,
 	     "Unexpected EFI_MEMORY_DESCRIPTOR version %ld",
 	     efi.memmap.desc_version);