[PATCH 03/11] efi: add API to reserve memory persistently across kexec reboot

Ard Biesheuvel
2018-09-27T08:51:06Z

Add kernel plumbing to reserve memory regions persistently on a EFI
system by adding entries to the MEMRESERVE linked list.

Tested-by: Jeremy Linton <jeremy.linton@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
drivers/firmware/efi/efi.c | 32 ++++++++++++++++++++++++++++++++
include/linux/efi.h | 1 +
2 files changed, 33 insertions(+)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 688132ac8a0a..249eb70691b0 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -962,6 +962,38 @@ bool efi_is_table_address(unsigned long phys_addr)
return false;
}

+static DEFINE_SPINLOCK(efi_mem_reserve_persistent_lock);
+
+int efi_mem_reserve_persistent(phys_addr_t addr, u64 size)
+{
+ struct linux_efi_memreserve *rsv, *parent;
+
+ if (efi.mem_reserve == EFI_INVALID_TABLE_ADDR)
+ return -ENODEV;
+
+ rsv = kmalloc(sizeof(*rsv), GFP_KERNEL);
+ if (!rsv)
+ return -ENOMEM;
+
+ parent = memremap(efi.mem_reserve, sizeof(*rsv), MEMREMAP_WB);
+ if (!parent) {
+ kfree(rsv);
+ return -ENOMEM;
+ }
+
+ rsv->base = addr;
+ rsv->size = size;
+
+ spin_lock(&efi_mem_reserve_persistent_lock);
+ rsv->next = parent->next;
+ parent->next = __pa(rsv);
+ spin_unlock(&efi_mem_reserve_persistent_lock);
+
+ memunmap(parent);
+
+ return 0;
+}
+
#ifdef CONFIG_KEXEC
static int update_efi_random_seed(struct notifier_block *nb,
unsigned long code, void *unused)
diff --git a/include/linux/efi.h b/include/linux/efi.h
index a5cb580472c5..22e4de9d3700 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1043,6 +1043,7 @@ extern int __init efi_uart_console_only (void);
extern u64 efi_mem_desc_end(efi_memory_desc_t *md);
extern int efi_mem_desc_lookup(u64 phys_addr, efi_memory_desc_t *out_md);
extern void efi_mem_reserve(phys_addr_t addr, u64 size);
+extern int efi_mem_reserve_persistent(phys_addr_t addr, u64 size);
extern void efi_initialize_iomem_resources(struct resource *code_resource,
struct resource *data_resource, struct resource *bss_resource);
extern void efi_reserve_boot_services(void);
--
2.18.0