linux-kernel - [PATCH] x86/mm: Unbreak modules that use the DMA API

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Date:   Fri, 15 Dec 2017 10:20:12 -0600
From:   Tom Lendacky <thomas.lendacky@....com>
To:     x86@...nel.org
Cc:     Brijesh Singh <brijesh.singh@....com>,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] x86/mm: Unbreak modules that use the DMA API

Commit d8aa7eea78a1 ("x86/mm: Add Secure Encrypted Virtualization (SEV)
support") changed sme_active() from an inline function that referenced
sme_me_mask to a non-inlined function in order to make the sev_enabled
variable a static variable.  This function was marked EXPORT_SYMBOL_GPL
because at the time the patch was submitted, sme_me_mask was marked
EXPORT_SYMBOL_GPL.

Commit 87df26175e67 ("x86/mm: Unbreak modules that rely on external
PAGE_KERNEL availability") changed sme_me_mask variable from
EXPORT_SYMBOL_GPL to EXPORT_SYMBOL, allowing external modules the ability
to build with CONFIG_AMD_MEM_ENCRYPT=y.  Now, however, with sev_active()
no longer an inline function and marked as EXPORT_SYMBOL_GPL, external
modules that use the DMA API are once again broken in 4.15. Since the DMA
API is meant to be used by external modules, this needs to be changed.

Change the sme_active() and sev_active() functions from EXPORT_SYMBOL_GPL
to EXPORT_SYMBOL.

Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
---
 arch/x86/mm/mem_encrypt.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index d9a9e9f..391b134 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -405,13 +405,13 @@ bool sme_active(void)
 {
 	return sme_me_mask && !sev_enabled;
 }
-EXPORT_SYMBOL_GPL(sme_active);
+EXPORT_SYMBOL(sme_active);

 bool sev_active(void)
 {
 	return sme_me_mask && sev_enabled;
 }
-EXPORT_SYMBOL_GPL(sev_active);
+EXPORT_SYMBOL(sev_active);

 static const struct dma_map_ops sev_dma_ops = {
 	.alloc                  = sev_alloc,