The UEFI spec 2.9 has recently been updated to include a requirement
that scatter-gather lists passed to UpdateCapsule() should be cleaned
from the D-cache to ensure that they are visible to the CPU after a
warm reboot before it enables the MMU. On ARM and arm64 systems, this
implies a D-cache clean by virtual address to the point of coherency.
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
arch/arm/include/asm/efi.h | 5 +++++
arch/arm64/include/asm/efi.h | 5 +++++
drivers/firmware/efi/capsule.c | 12 ++++++++++++
3 files changed, 22 insertions(+)
diff --git a/arch/arm/include/asm/efi.h b/arch/arm/include/asm/efi.h
index 3ee4f4381985..e9a06e164e06 100644
--- a/arch/arm/include/asm/efi.h
+++ b/arch/arm/include/asm/efi.h
@@ -93,4 +93,9 @@ struct efi_arm_entry_state {
u32 sctlr_after_ebs;
};
+static inline void efi_capsule_flush_cache_range(void *addr, int size)
+{
+ __cpuc_flush_dcache_area(addr, size);
+}
+
#endif /* _ASM_ARM_EFI_H */
diff --git a/arch/arm64/include/asm/efi.h b/arch/arm64/include/asm/efi.h
index 973b14415271..00bd1e179d36 100644
--- a/arch/arm64/include/asm/efi.h
+++ b/arch/arm64/include/asm/efi.h
@@ -141,4 +141,9 @@ static inline void efi_set_pgd(struct mm_struct *mm)
void efi_virtmap_load(void);
void efi_virtmap_unload(void);
+static inline void efi_capsule_flush_cache_range(void *addr, int size)
+{
+ __flush_dcache_area(addr, size);
+}
+
#endif /* _ASM_EFI_H */
diff --git a/drivers/firmware/efi/capsule.c b/drivers/firmware/efi/capsule.c
index 43f6fe7bfe80..768430293669 100644
--- a/drivers/firmware/efi/capsule.c
+++ b/drivers/firmware/efi/capsule.c
@@ -12,6 +12,7 @@
#include <linux/highmem.h>
#include <linux/efi.h>
#include <linux/vmalloc.h>
+#include <asm/efi.h>
#include <asm/io.h>
typedef struct {
@@ -265,6 +266,17 @@ int efi_capsule_update(efi_capsule_header_t *capsule, phys_addr_t *pages)
else
sglist[j].data = page_to_phys(sg_pages[i + 1]);
+#if defined(CONFIG_ARM) || defined(CONFIG_ARM64)
+ /*
+ * At runtime, the firmware has no way to find out where the
+ * sglist elements are mapped, if they are mapped in the first
+ * place. Therefore, on architectures that can only perform
+ * cache maintenance by virtual address, the firmware is unable
+ * to perform this maintenance, and so it is up to the OS to do
+ * it instead.
+ */
+ efi_capsule_flush_cache_range(sglist, PAGE_SIZE);
+#endif
kunmap_atomic(sglist);
}
--
2.17.1
