linux-kernel - [PATCH v2 04/19] powerpc/kvm: Prefer fault_in_pages

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Date:   Wed, 28 Mar 2018 21:58:11 +0200
From:   Mathieu Malaterre <malat@...ian.org>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     LEROY Christophe <christophe.leroy@....fr>,
        Mathieu Malaterre <malat@...ian.org>,
        Paul Mackerras <paulus@...abs.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        kvm-ppc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 04/19] powerpc/kvm: Prefer fault_in_pages_readable function

Directly use fault_in_pages_readable instead of manual __get_user code. Fix
warning treated as error with W=1:

  arch/powerpc/kernel/kvm.c:675:6: error: variable ‘tmp’ set but not used [-Werror=unused-but-set-variable]

Suggested-by: Christophe Leroy <christophe.leroy@....fr>
Signed-off-by: Mathieu Malaterre <malat@...ian.org>
---
v2: use fault_in_pages_readable instead
 arch/powerpc/kernel/kvm.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/kvm.c b/arch/powerpc/kernel/kvm.c
index 9ad37f827a97..124c51030b75 100644
--- a/arch/powerpc/kernel/kvm.c
+++ b/arch/powerpc/kernel/kvm.c
@@ -25,6 +25,7 @@
 #include <linux/kvm_para.h>
 #include <linux/slab.h>
 #include <linux/of.h>
+#include <linux/pagemap.h>
 
 #include <asm/reg.h>
 #include <asm/sections.h>
@@ -672,14 +673,13 @@ static void kvm_use_magic_page(void)
 {
 	u32 *p;
 	u32 *start, *end;
-	u32 tmp;
 	u32 features;
 
 	/* Tell the host to map the magic page to -4096 on all CPUs */
 	on_each_cpu(kvm_map_magic_page, &features, 1);
 
 	/* Quick self-test to see if the mapping works */
-	if (__get_user(tmp, (u32*)KVM_MAGIC_PAGE)) {
+	if (!fault_in_pages_readable((const char *)KVM_MAGIC_PAGE, sizeof(u32))) {
 		kvm_patching_worked = false;
 		return;
 	}
-- 
2.11.0