linux-kernel - [patch] x86/mm: Free sme_early

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Date:   Wed, 10 Jul 2019 13:19:35 -0700 (PDT)
From:   David Rientjes <rientjes@...gle.com>
To:     Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>
cc:     Cfir Cohen <cfir@...gle.com>,
        Thomas Lendacky <Thomas.Lendacky@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: [patch] x86/mm: Free sme_early_buffer after init

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@...gle.com>
Signed-off-by: David Rientjes <rientjes@...gle.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