x86/ioremap: Map EFI runtime services data as encrypted for SEV

The dmidecode program fails to properly decode the SMBIOS data supplied
by OVMF/UEFI when running in an SEV guest. The SMBIOS area, under SEV, is
encrypted and resides in reserved memory that is marked as EFI runtime
services data.

As a result, when memremap() is attempted for the SMBIOS data, it
can't be mapped as regular RAM (through try_ram_remap()) and, since
the address isn't part of the iomem resources list, it isn't mapped
encrypted through the fallback ioremap().

Add a new __ioremap_check_other() to deal with memory types like
EFI_RUNTIME_SERVICES_DATA which are not covered by the resource ranges.

This allows any runtime services data which has been created encrypted,
to be mapped encrypted too.

 [ bp: Move functionality to a separate function. ]

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Joerg Roedel <jroedel@suse.de>
Tested-by: Joerg Roedel <jroedel@suse.de>
Cc: <stable@vger.kernel.org> # 5.3
Link: https://lkml.kernel.org/r/2d9e16eb5b53dc82665c95c6764b7407719df7a0.1582645327.git.thomas.lendacky@amd.com

arch/x86/mm/ioremap.c

@@ -106,6 +106,19 @@ static unsigned int __ioremap_check_encrypted(struct resource *res)
 	return 0;
 }
 
+/*
+ * The EFI runtime services data area is not covered by walk_mem_res(), but must
+ * be mapped encrypted when SEV is active.
+ */
+static void __ioremap_check_other(resource_size_t addr, struct ioremap_desc *desc)
+{
+	if (!sev_active())
+		return;
+
+	if (efi_mem_type(addr) == EFI_RUNTIME_SERVICES_DATA)
+		desc->flags |= IORES_MAP_ENCRYPTED;
+}
+
 static int __ioremap_collect_map_flags(struct resource *res, void *arg)
 {
 	struct ioremap_desc *desc = arg;
@@ -124,6 +137,9 @@ static int __ioremap_collect_map_flags(struct resource *res, void *arg)
  * To avoid multiple resource walks, this function walks resources marked as
  * IORESOURCE_MEM and IORESOURCE_BUSY and looking for system RAM and/or a
  * resource described not as IORES_DESC_NONE (e.g. IORES_DESC_ACPI_TABLES).
+ *
+ * After that, deal with misc other ranges in __ioremap_check_other() which do
+ * not fall into the above category.
  */
 static void __ioremap_check_mem(resource_size_t addr, unsigned long size,
 				struct ioremap_desc *desc)
@@ -135,6 +151,8 @@ static void __ioremap_check_mem(resource_size_t addr, unsigned long size,
 	memset(desc, 0, sizeof(struct ioremap_desc));
 
 	walk_mem_res(start, end, desc, __ioremap_collect_map_flags);
+
+	__ioremap_check_other(addr, desc);
 }
 
 /*