[patch] x86/mm: Free sme_early_buffer after init

[patch] x86/mm: Free sme_early_buffer after init

[David Rientjes]

We want to be able to clear the contents of sme_early_buffer after
__sme_early_enc_dec() because it is used to move encrypted and decrypted
data, but since __sme_early_enc_dec() is __init we can simply free this
buffer after init.

This saves a page that is otherwise unreferenced after init.

Reported-by: Cfir Cohen <cfir@google.com>
Signed-off-by: David Rientjes <rientjes@google.com>
---
 arch/x86/mm/mem_encrypt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -41,7 +41,7 @@ EXPORT_SYMBOL_GPL(sev_enable_key);
 bool sev_enabled __section(.data);
 
 /* Buffer used for early in-place encryption by BSP, no locking needed */
-static char sme_early_buffer[PAGE_SIZE] __aligned(PAGE_SIZE);
+static char sme_early_buffer[PAGE_SIZE] __initdata __aligned(PAGE_SIZE);
 
 /*
  * This routine does not change the underlying encryption setting of the

[tip:x86/urgent] x86/mm: Free sme_early_buffer after init

[tip-bot for David Rientjes]

Commit-ID:  ffdb07f31252625b7bcbf1f424d7beccff02ba97
Gitweb:     https://git.kernel.org/tip/ffdb07f31252625b7bcbf1f424d7beccff02ba97
Author:     David Rientjes <rientjes@google.com>
AuthorDate: Wed, 10 Jul 2019 13:19:35 -0700
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 16 Jul 2019 23:13:48 +0200

x86/mm: Free sme_early_buffer after init

The contents of sme_early_buffer should be cleared after
__sme_early_enc_dec() because it is used to move encrypted and decrypted
data, but since __sme_early_enc_dec() is __init this buffer simply can be
freed after init.

This saves a page that is otherwise unreferenced after init.

Reported-by: Cfir Cohen <cfir@google.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1907101318170.197432@chino.kir.corp.google.com

---
 arch/x86/mm/mem_encrypt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index e0df96fdfe46..e94e0a62ba92 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -41,7 +41,7 @@ EXPORT_SYMBOL_GPL(sev_enable_key);
 bool sev_enabled __section(.data);
 
 /* Buffer used for early in-place encryption by BSP, no locking needed */
-static char sme_early_buffer[PAGE_SIZE] __aligned(PAGE_SIZE);
+static char sme_early_buffer[PAGE_SIZE] __initdata __aligned(PAGE_SIZE);
 
 /*
  * This routine does not change the underlying encryption setting of the