[PATCH 4/6] x86/efi: Free existing memory map before installing new memory map

[Sai Praneeth Prakhya]

From: Sai Praneeth <sai.praneeth.prakhya@xxxxxxxxx>

efi_memmap_install(), unmaps the existing memory map and installs a new
memory map but doesn't free the memory allocated to the existing
memory map. Fortunately, the details about the existing memory map (like
the physical address, number of entries and type of memory) are
stored in efi.memmap. Hence, use them to free the memory.

In __efi_enter_virtual_mode(), we don't use efi_memmap_install() to
install a new memory map, instead we use efi_memmap_init_late(). Hence,
free existing memory map there too before installing a new memory map.

Generally, memory for new memory map is allocated using
efi_memmap_alloc() but in __efi_enter_virtual_mode() it's done using
realloc_pages() [please see efi_map_regions()]. So, it's OK to free this
memory using efi_memmap_free() in efi_free_boot_services().

Also, note that the first time efi_free_memmap() is called either from
efi_fake_memmap() or efi_arch_mem_reserve() [depending on the boot
sequence], we are actually freeing memblock_reserved memory which isn't
allocated by efi_memmap_alloc(). So, there are two outliers where we use
efi_free_memmap() to free memory allocated through other sources
rather than efi_memmap_alloc().

Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@xxxxxxxxx>
Suggested-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Cc: Lee Chun-Yi <jlee@xxxxxxxx>
Cc: Dave Young <dyoung@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Laszlo Ersek <lersek@xxxxxxxxxx>
Cc: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Bhupesh Sharma <bhsharma@xxxxxxxxxx>
Cc: Nicolai Stange <nicstange@xxxxxxxxx>
Cc: Naresh Bhat <naresh.bhat@xxxxxxxxxx>
Cc: Ricardo Neri <ricardo.neri@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Taku Izumi <izumi.taku@xxxxxxxxxxxxxx>
Cc: Ravi Shankar <ravi.v.shankar@xxxxxxxxx>
Cc: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
---
 arch/x86/platform/efi/efi.c     | 3 +++
 arch/x86/platform/efi/quirks.c  | 6 ++++++
 drivers/firmware/efi/fake_mem.c | 3 +++
 3 files changed, 12 insertions(+)

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index cda54abf25a6..7756426e93b5 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -952,6 +952,9 @@ static void __init __efi_enter_virtual_mode(void)
 	 * firmware via SetVirtualAddressMap().
 	 */
 	efi_memmap_unmap();
+	/* Free existing memory map before installing new memory map */
+	efi_memmap_free(efi.memmap.phys_map, efi.memmap.nr_map,
+			efi.memmap.alloc_type);
 
 	if (efi_memmap_init_late(pa, efi.memmap.desc_size * count)) {
 		pr_err("Failed to remap late EFI memory map\n");
diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
index 11fa6ac9f0c2..11800f3cbb93 100644
--- a/arch/x86/platform/efi/quirks.c
+++ b/arch/x86/platform/efi/quirks.c
@@ -292,6 +292,9 @@ void __init efi_arch_mem_reserve(phys_addr_t addr, u64 size)
 	efi_memmap_insert(&efi.memmap, new, &mr);
 	early_memunmap(new, new_size);
 
+	/* Free existing memory map before installing new memory map */
+	efi_memmap_free(efi.memmap.phys_map, efi.memmap.nr_map,
+			efi.memmap.alloc_type);
 	efi_memmap_install(new_phys, num_entries, alloc_type);
 }
 
@@ -452,6 +455,9 @@ void __init efi_free_boot_services(void)
 
 	memunmap(new);
 
+	/* Free existing memory map before installing new memory map */
+	efi_memmap_free(efi.memmap.phys_map, efi.memmap.nr_map,
+			efi.memmap.alloc_type);
 	if (efi_memmap_install(new_phys, num_entries, alloc_type)) {
 		pr_err("Could not install new EFI memmap\n");
 		return;
diff --git a/drivers/firmware/efi/fake_mem.c b/drivers/firmware/efi/fake_mem.c
index 82dcfa1c340b..a47754efb796 100644
--- a/drivers/firmware/efi/fake_mem.c
+++ b/drivers/firmware/efi/fake_mem.c
@@ -90,6 +90,9 @@ void __init efi_fake_memmap(void)
 	/* swap into new EFI memmap */
 	early_memunmap(new_memmap, efi.memmap.desc_size * new_nr_map);
 
+	/* Free existing memory map before installing new memory map */
+	efi_memmap_free(efi.memmap.phys_map, efi.memmap.nr_map,
+			efi.memmap.alloc_type);
 	efi_memmap_install(new_memmap_phy, new_nr_map, alloc_type);
 
 	/* print new EFI memmap */
-- 
2.7.4