linux-kernel - Re: SME/32-bit regression

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Date:   Wed, 6 Sep 2017 11:26:18 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc:     thomas.lendacky@....com, X86 ML <x86@...nel.org>,
        "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: Re: SME/32-bit regression

On Tue, Sep 05, 2017 at 11:45:07PM -0400, Boris Ostrovsky wrote:
> It appears there is a regression for 32-bit kernels due to SME changes.
> 
> I bisected my particular problem

It being? Doesn't boot, splats?

> (Xen PV guest) to
> 21729f81ce8ae76a6995681d40e16f7ce8075db4 but I also saw pmd_clear_bad()
> errors on baremetal. This seems to be caused by sme_me_mask being an
> unsigned long as opposed to phys_addr_t (the actual problem is that
> __PHYSICAL_MASK is truncated). When I declare it as u64 and drop unsigned
> long cast in __sme_set()/__sme_clr() the problem goes way. (This presumably
> won't work for non-PAE which I haven't tried).

Right, so I think we should do this because those macros should not have
any effect on !CONFIG_AMD_MEM_ENCRYPT setups.

---
diff --git a/include/linux/mem_encrypt.h b/include/linux/mem_encrypt.h
index 1255f09f5e42..823eec6ba951 100644
--- a/include/linux/mem_encrypt.h
+++ b/include/linux/mem_encrypt.h
@@ -35,6 +35,7 @@ static inline unsigned long 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
@@ -42,6 +43,10 @@ static inline unsigned long sme_get_me_mask(void)
  */
 #define __sme_set(x)		((unsigned long)(x) | sme_me_mask)
 #define __sme_clr(x)		((unsigned long)(x) & ~sme_me_mask)
+#else
+#define __sme_set(x)		(x)
+#define __sme_clr(x)		(x)
+#endif
 
 #endif	/* __ASSEMBLY__ */
 



-- 
Regards/Gruss,
    Boris.

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