From: "Jonathan (Zhixiong) Zhang" <zjzhang@xxxxxxxxxxxxxx>
If it is a EFI system, if EFI memmap is enabled and if
a memory region has attribute of EFI_MEMORY_UC, map it as uncached.
On x86, EFI memmap is unmapped in efi_free_boot_services(),
before kernel finishes booting. So when efi_remap() is called
during runtime on x86, it maps the region as cached.
Signed-off-by: Jonathan (Zhixiong) Zhang <zjzhang@xxxxxxxxxxxxxx>
---
drivers/firmware/efi/efi.c | 9 +++++++++
include/linux/efi.h | 1 +
2 files changed, 10 insertions(+)
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 86da85368778..5b42bb6d1fde 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -535,3 +535,12 @@ u64 efi_mem_attributes(unsigned long phys_addr)
}
return 0;
}
+
+void __iomem *efi_remap(phys_addr_t phys_addr, size_t size)
+{
+ if (efi_enabled(EFI_MEMMAP) &&
+ (efi_mem_attributes(phys_addr) & EFI_MEMORY_UC))
+ return ioremap(phys_addr, size);
+ else
+ return ioremap_cache(phys_addr, size);
+}
diff --git a/include/linux/efi.h b/include/linux/efi.h
index af5be0368dec..0a0aa25d44d7 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -888,6 +888,7 @@ extern void efi_get_time(struct timespec *now);
extern void efi_reserve_boot_services(void);
extern int efi_get_fdt_params(struct efi_fdt_params *params, int verbose);
extern struct efi_memory_map memmap;
+extern void __iomem *efi_remap(phys_addr_t phys_addr, size_t size);
extern int efi_reboot_quirk_mode;
extern bool efi_poweroff_required(void);
--
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