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Subject[PATCH v6 23/34] x86, realmode: Decrypt trampoline area if memory encryption is active
Date
When Secure Memory Encryption is enabled, the trampoline area must not
be encrypted. A CPU running in real mode will not be able to decrypt
memory that has been encrypted because it will not be able to use addresses
with the memory encryption mask.

A recent change that added a new system_state value exposed a warning
issued by early_ioreamp() when the system_state was not SYSTEM_BOOTING.
At the stage where the trampoline area is decrypted, the system_state is
now SYSTEM_SCHEDULING. The check was changed to issue a warning if the
system_state is greater than or equal to SYSTEM_RUNNING.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
arch/x86/realmode/init.c | 11 +++++++++++
mm/early_ioremap.c | 2 +-
2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c
index a163a90..195ba29 100644
--- a/arch/x86/realmode/init.c
+++ b/arch/x86/realmode/init.c
@@ -6,6 +6,7 @@
#include <asm/pgtable.h>
#include <asm/realmode.h>
#include <asm/tlbflush.h>
+#include <asm/mem_encrypt.h>

struct real_mode_header *real_mode_header;
u32 *trampoline_cr4_features;
@@ -130,6 +131,16 @@ static void __init set_real_mode_permissions(void)
unsigned long text_start =
(unsigned long) __va(real_mode_header->text_start);

+ /*
+ * If SME is active, the trampoline area will need to be in
+ * decrypted memory in order to bring up other processors
+ * successfully.
+ */
+ if (sme_active()) {
+ sme_early_decrypt(__pa(base), size);
+ set_memory_decrypted((unsigned long)base, size >> PAGE_SHIFT);
+ }
+
set_memory_nx((unsigned long) base, size >> PAGE_SHIFT);
set_memory_ro((unsigned long) base, ro_size >> PAGE_SHIFT);
set_memory_x((unsigned long) text_start, text_size >> PAGE_SHIFT);
diff --git a/mm/early_ioremap.c b/mm/early_ioremap.c
index b1dd4a9..01d13ae 100644
--- a/mm/early_ioremap.c
+++ b/mm/early_ioremap.c
@@ -110,7 +110,7 @@ static int __init check_early_ioremap_leak(void)
enum fixed_addresses idx;
int i, slot;

- WARN_ON(system_state != SYSTEM_BOOTING);
+ WARN_ON(system_state >= SYSTEM_RUNNING);

slot = -1;
for (i = 0; i < FIX_BTMAPS_SLOTS; i++) {
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