[PATCH V2 2/3] efi: add efi_remap()

["Jonathan (Zhixiong) Zhang" <zjzhang-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>]

From: "Jonathan (Zhixiong) Zhang" <zjzhang-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>

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-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
---
 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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