[PATCH] x86/efi: Add necessary checks before iterating over efi.memmap

[Chao Gao <chao.gao-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

Commit 78ce248f (efi: Iterate over efi.memmap in for_each_efi_memory_desc())
replaces the old loop by for_each_efi_memory_desc() which will encounter #PF
when efi.memap are not initialized.

In boot process, xen set EFI_PARAVIRT in xen_efi_init() before setup_arch()
is called. This leads efi_memmap_init() will not initialize structures
related to efi.memmap. However, the following functions e.g.
efi_find_mirror(), efi_print_memmap() and efi_free_boot_services() access
efi.memmap without necessary checks. kernel and xen crash in this case.
After adding these checks, xen and kernel boot up normally.

Signed-off-by: Chao Gao <chao.gao-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
---
 arch/x86/platform/efi/efi.c    | 6 ++++++
 arch/x86/platform/efi/quirks.c | 3 +++
 2 files changed, 9 insertions(+)

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 1fbb408..68966dc 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -102,6 +102,9 @@ void __init efi_find_mirror(void)
 	efi_memory_desc_t *md;
 	u64 mirror_size = 0, total_size = 0;
 
+	if (efi_enabled(EFI_PARAVIRT))
+		return;
+
 	for_each_efi_memory_desc(md) {
 		unsigned long long start = md->phys_addr;
 		unsigned long long size = md->num_pages << EFI_PAGE_SHIFT;
@@ -207,6 +210,9 @@ void __init efi_print_memmap(void)
 	efi_memory_desc_t *md;
 	int i = 0;
 
+	if (efi_enabled(EFI_PARAVIRT))
+		return;
+
 	for_each_efi_memory_desc(md) {
 		char buf[64];
 
diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
index 89d1146..4fa1e4d 100644
--- a/arch/x86/platform/efi/quirks.c
+++ b/arch/x86/platform/efi/quirks.c
@@ -251,6 +251,9 @@ void __init efi_free_boot_services(void)
 {
 	efi_memory_desc_t *md;
 
+	if (efi_enabled(EFI_PARAVIRT))
+		return;
+
 	for_each_efi_memory_desc(md) {
 		unsigned long long start = md->phys_addr;
 		unsigned long long size = md->num_pages << EFI_PAGE_SHIFT;
-- 
1.8.3.1