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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.19 23/74] x86: kvm: avoid constant-conversion warning
Date:   Mon,  5 Aug 2019 15:02:36 +0200
Message-Id: <20190805124937.642225390@linuxfoundation.org>
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[ Upstream commit a6a6d3b1f867d34ba5bd61aa7bb056b48ca67cff ]

clang finds a contruct suspicious that converts an unsigned
character to a signed integer and back, causing an overflow:

arch/x86/kvm/mmu.c:4605:39: error: implicit conversion from 'int' to 'u8' (aka 'unsigned char') changes value from -205 to 51 [-Werror,-Wconstant-conversion]
                u8 wf = (pfec & PFERR_WRITE_MASK) ? ~w : 0;
                   ~~                               ^~
arch/x86/kvm/mmu.c:4607:38: error: implicit conversion from 'int' to 'u8' (aka 'unsigned char') changes value from -241 to 15 [-Werror,-Wconstant-conversion]
                u8 uf = (pfec & PFERR_USER_MASK) ? ~u : 0;
                   ~~                              ^~
arch/x86/kvm/mmu.c:4609:39: error: implicit conversion from 'int' to 'u8' (aka 'unsigned char') changes value from -171 to 85 [-Werror,-Wconstant-conversion]
                u8 ff = (pfec & PFERR_FETCH_MASK) ? ~x : 0;
                   ~~                               ^~

Add an explicit cast to tell clang that everything works as
intended here.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://github.com/ClangBuiltLinux/linux/issues/95
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/x86/kvm/mmu.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index e0f982e35c96b..cdc0c460950f3 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4532,11 +4532,11 @@ static void update_permission_bitmask(struct kvm_vcpu *vcpu,
 		 */
 
 		/* Faults from writes to non-writable pages */
-		u8 wf = (pfec & PFERR_WRITE_MASK) ? ~w : 0;
+		u8 wf = (pfec & PFERR_WRITE_MASK) ? (u8)~w : 0;
 		/* Faults from user mode accesses to supervisor pages */
-		u8 uf = (pfec & PFERR_USER_MASK) ? ~u : 0;
+		u8 uf = (pfec & PFERR_USER_MASK) ? (u8)~u : 0;
 		/* Faults from fetches of non-executable pages*/
-		u8 ff = (pfec & PFERR_FETCH_MASK) ? ~x : 0;
+		u8 ff = (pfec & PFERR_FETCH_MASK) ? (u8)~x : 0;
 		/* Faults from kernel mode fetches of user pages */
 		u8 smepf = 0;
 		/* Faults from kernel mode accesses of user pages */
-- 
2.20.1