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Subject[PATCH 09/11] efi: permit multiple entries in persistent memreserve data structure
Date
In preparation of updating efi_mem_reserve_persistent() to cause less
fragmentation when dealing with many persistent reservations, update
the struct definition and the code that handles it currently so it
can describe an arbitrary number of reservations using a single linked
list entry. The actual optimization will be implemented in a subsequent
patch.

Tested-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
drivers/firmware/efi/efi.c | 39 +++++++++++++++++--------
drivers/firmware/efi/libstub/arm-stub.c | 2 +-
include/linux/efi.h | 13 +++++++--
3 files changed, 38 insertions(+), 16 deletions(-)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 415849bab233..80b11521627a 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -602,21 +602,33 @@ int __init efi_apply_persistent_mem_reservations(void)

while (prsv) {
struct linux_efi_memreserve *rsv;
-
- /* reserve the entry itself */
- memblock_reserve(prsv, sizeof(*rsv));
-
- rsv = early_memremap(prsv, sizeof(*rsv));
- if (rsv == NULL) {
+ u8 *p;
+ int i;
+
+ /*
+ * Just map a full page: that is what we will get
+ * anyway, and it permits us to map the entire entry
+ * before knowing its size.
+ */
+ p = early_memremap(ALIGN_DOWN(prsv, PAGE_SIZE),
+ PAGE_SIZE);
+ if (p == NULL) {
pr_err("Could not map UEFI memreserve entry!\n");
return -ENOMEM;
}

- if (rsv->size)
- memblock_reserve(rsv->base, rsv->size);
+ rsv = (void *)(p + prsv % PAGE_SIZE);
+
+ /* reserve the entry itself */
+ memblock_reserve(prsv, EFI_MEMRESERVE_SIZE(rsv->size));
+
+ for (i = 0; i < atomic_read(&rsv->count); i++) {
+ memblock_reserve(rsv->entry[i].base,
+ rsv->entry[i].size);
+ }

prsv = rsv->next;
- early_memunmap(rsv, sizeof(*rsv));
+ early_memunmap(p, PAGE_SIZE);
}
}

@@ -985,6 +997,7 @@ static int __init efi_memreserve_map_root(void)
int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size)
{
struct linux_efi_memreserve *rsv;
+ int rsvsize = EFI_MEMRESERVE_SIZE(1);
int rc;

if (efi_memreserve_root == (void *)ULONG_MAX)
@@ -996,12 +1009,14 @@ int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size)
return rc;
}

- rsv = kmalloc(sizeof(*rsv), GFP_ATOMIC);
+ rsv = kmalloc(rsvsize, GFP_ATOMIC);
if (!rsv)
return -ENOMEM;

- rsv->base = addr;
- rsv->size = size;
+ rsv->size = 1;
+ atomic_set(&rsv->count, 1);
+ rsv->entry[0].base = addr;
+ rsv->entry[0].size = size;

spin_lock(&efi_mem_reserve_persistent_lock);
rsv->next = efi_memreserve_root->next;
diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c
index 3d36142cf812..9e20159ea5f5 100644
--- a/drivers/firmware/efi/libstub/arm-stub.c
+++ b/drivers/firmware/efi/libstub/arm-stub.c
@@ -86,8 +86,8 @@ void install_memreserve_table(efi_system_table_t *sys_table_arg)
}

rsv->next = 0;
- rsv->base = 0;
rsv->size = 0;
+ atomic_set(&rsv->count, 0);

status = efi_call_early(install_configuration_table,
&memreserve_table_guid,
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 2b3b33c83b05..4f27640fdcdc 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1712,9 +1712,16 @@ extern struct efi_runtime_work efi_rts_work;
extern struct workqueue_struct *efi_rts_wq;

struct linux_efi_memreserve {
- phys_addr_t next;
- phys_addr_t base;
- phys_addr_t size;
+ int size; // allocated size of the array
+ atomic_t count; // number of entries used
+ phys_addr_t next; // pa of next struct instance
+ struct {
+ phys_addr_t base;
+ phys_addr_t size;
+ } entry[0];
};

+#define EFI_MEMRESERVE_SIZE(count) (sizeof(struct linux_efi_memreserve) + \
+ (count) * sizeof(((struct linux_efi_memreserve *)0)->entry[0]))
+
#endif /* _LINUX_EFI_H */
--
2.19.1
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