linux-kernel - [PATCH] x86/mm: Make the SME mask a u64

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Date:   Thu, 7 Sep 2017 11:38:37 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     x86-ml <x86@...nel.org>
Cc:     Brijesh Singh <brijesh.singh@....com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        "Lendacky, Thomas" <Thomas.Lendacky@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] x86/mm: Make the SME mask a u64

On Wed, Sep 06, 2017 at 07:26:40PM -0500, Brijesh Singh wrote:
> 32-bit seems to be working well - thanks

Thanks Boris and Brijesh for testing!

---
From: Borislav Petkov <bp@...e.de>

The SME encryption mask is for masking 64-bit pagetable entries. It
being an unsigned long works fine on X86_64 but on 32-bit builds in
truncates bits leading to Xen guests crashing very early.

And regardless, the whole SME mask handling shouldnt've leaked into
32-bit because SME is X86_64-only feature. So, first make the mask u64.
And then, add trivial 32-bit versions of the __sme_* macros so that
nothing happens there.

Reported-and-tested-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Tested-by: Brijesh Singh <brijesh.singh@....com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Acked-by: Tom Lendacky <Thomas.Lendacky@....com>
Fixes: 21729f81ce8a ("x86/mm: Provide general kernel support for memory encryption")
---
 arch/x86/include/asm/mem_encrypt.h |  4 ++--
 arch/x86/mm/mem_encrypt.c          |  2 +-
 include/linux/mem_encrypt.h        | 13 +++++++++----
 3 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
index 8e618fcf1f7c..6a77c63540f7 100644
--- a/arch/x86/include/asm/mem_encrypt.h
+++ b/arch/x86/include/asm/mem_encrypt.h
@@ -21,7 +21,7 @@
 
 #ifdef CONFIG_AMD_MEM_ENCRYPT
 
-extern unsigned long sme_me_mask;
+extern u64 sme_me_mask;
 
 void sme_encrypt_execute(unsigned long encrypted_kernel_vaddr,
 			 unsigned long decrypted_kernel_vaddr,
@@ -49,7 +49,7 @@ void swiotlb_set_mem_attributes(void *vaddr, unsigned long size);
 
 #else	/* !CONFIG_AMD_MEM_ENCRYPT */
 
-#define sme_me_mask	0UL
+#define sme_me_mask	0ULL
 
 static inline void __init sme_early_encrypt(resource_size_t paddr,
 					    unsigned long size) { }
diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index 0fbd09269757..3fcc8e01683b 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -37,7 +37,7 @@ static char sme_cmdline_off[] __initdata = "off";
  * reside in the .data section so as not to be zeroed out when the .bss
  * section is later cleared.
  */
-unsigned long sme_me_mask __section(.data) = 0;
+u64 sme_me_mask __section(.data) = 0;
 EXPORT_SYMBOL_GPL(sme_me_mask);
 
 /* Buffer used for early in-place encryption by BSP, no locking needed */
diff --git a/include/linux/mem_encrypt.h b/include/linux/mem_encrypt.h
index 1255f09f5e42..265a9cd21cb4 100644
--- a/include/linux/mem_encrypt.h
+++ b/include/linux/mem_encrypt.h
@@ -21,7 +21,7 @@
 
 #else	/* !CONFIG_ARCH_HAS_MEM_ENCRYPT */
 
-#define sme_me_mask	0UL
+#define sme_me_mask	0ULL
 
 #endif	/* CONFIG_ARCH_HAS_MEM_ENCRYPT */
 
@@ -30,18 +30,23 @@ static inline bool sme_active(void)
 	return !!sme_me_mask;
 }
 
-static inline unsigned long sme_get_me_mask(void)
+static inline u64 sme_get_me_mask(void)
 {
 	return sme_me_mask;
 }
 
+#ifdef CONFIG_AMD_MEM_ENCRYPT
 /*
  * The __sme_set() and __sme_clr() macros are useful for adding or removing
  * the encryption mask from a value (e.g. when dealing with pagetable
  * entries).
  */
-#define __sme_set(x)		((unsigned long)(x) | sme_me_mask)
-#define __sme_clr(x)		((unsigned long)(x) & ~sme_me_mask)
+#define __sme_set(x)		((x) | sme_me_mask)
+#define __sme_clr(x)		((x) & ~sme_me_mask)
+#else
+#define __sme_set(x)		(x)
+#define __sme_clr(x)		(x)
+#endif
 
 #endif	/* __ASSEMBLY__ */
 
-- 
2.13.0

-- 
Regards/Gruss,
    Boris.

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