@@ -978,22 +978,35 @@ 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;
- int rsvsize = EFI_MEMRESERVE_SIZE(1);
+ unsigned long prsv;
+ int index;
if (efi.mem_reserve == EFI_INVALID_TABLE_ADDR)
return -ENODEV;
- rsv = kmalloc(rsvsize, GFP_KERNEL);
- if (!rsv)
- return -ENOMEM;
-
parent = memremap(efi.mem_reserve, sizeof(*rsv), MEMREMAP_WB);
- if (!parent) {
- kfree(rsv);
+ if (!parent)
return -ENOMEM;
+
+ /* first try to find a slot in an existing linked list entry */
+ for (prsv = parent->next; prsv; prsv = rsv->next) {
+ rsv = __va(prsv);
+ index = atomic_fetch_add_unless(&rsv->count, 1, rsv->size);
+ if (index < rsv->size) {
+ rsv->entry[index].base = addr;
+ rsv->entry[index].size = size;
+
+ memunmap(parent);
+ return 0;
+ }
}
- rsv->size = 1;
+ /* no slot found - allocate a new linked list entry */
+ rsv = (struct linux_efi_memreserve *)__get_free_page(GFP_KERNEL);
+ if (!rsv)
+ return -ENOMEM;
+
+ rsv->size = EFI_MEMRESERVE_COUNT(PAGE_SIZE);
atomic_set(&rsv->count, 1);
rsv->entry[0].base = addr;
rsv->entry[0].size = size;
@@ -1727,4 +1727,7 @@ struct linux_efi_memreserve {
#define EFI_MEMRESERVE_SIZE(count) (sizeof(struct linux_efi_memreserve) + \
(count) * sizeof(((struct linux_efi_memreserve *)0)->entry[0]))
+#define EFI_MEMRESERVE_COUNT(size) (((size) - sizeof(struct linux_efi_memreserve)) \
+ / sizeof(((struct linux_efi_memreserve *)0)->entry[0]))
+
#endif /* _LINUX_EFI_H */
The current implementation of efi_mem_reserve_persistent() is rather naive, in the sense that for each invocation, it creates a separate linked list entry to describe the reservation. Since the linked list entries themselves need to persist across subsequent kexec reboots, every reservation created this way results in two memblock_reserve() calls at the next boot. On arm64 systems with 100s of CPUs, this may result in a excessive number of memblock reservations, and needless fragmentation. So instead, make use of the newly updated struct linux_efi_memreserve layout to put multiple reservations into a single linked list entry. This should get rid of the numerous tiny memblock reservations, and effectively cut the total number of reservations in half on arm64 systems with many CPUs. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- drivers/firmware/efi/efi.c | 29 ++++++++++++++------ include/linux/efi.h | 3 ++ 2 files changed, 24 insertions(+), 8 deletions(-) -- 2.19.1