From: Arnd Bergmann <arnd@arndb.de>
To: "Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>,
x86@kernel.org
Cc: Arnd Bergmann <arnd@arndb.de>, "H. Peter Anvin" <hpa@zytor.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
Junaid Shahid <junaids@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Lan Tianyu <Tianyu.Lan@microsoft.com>,
Wei Yang <richard.weiyang@gmail.com>,
Kai Huang <kai.huang@linux.intel.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
clang-built-linux@googlegroups.com
Subject: [PATCH 2/2] x86: kvm: avoid constant-conversion warning
Date: Fri, 12 Jul 2019 11:12:30 +0200 [thread overview]
Message-ID: <20190712091239.716978-2-arnd@arndb.de> (raw)
In-Reply-To: <20190712091239.716978-1-arnd@arndb.de>
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>
---
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 17ece7b994b1..aea7f969ecb8 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4602,11 +4602,11 @@ 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 */
--
2.20.0
next prev parent reply other threads:[~2019-07-12 9:13 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-12 9:12 [PATCH 1/2] x86: kvm: avoid -Wsometimes-uninitized warning Arnd Bergmann
2019-07-12 9:12 ` Arnd Bergmann [this message]
2019-07-12 9:30 ` [PATCH 2/2] x86: kvm: avoid constant-conversion warning Sedat Dilek
2019-07-12 17:47 ` Paolo Bonzini
2019-07-12 12:02 ` [PATCH 1/2] x86: kvm: avoid -Wsometimes-uninitized warning Roman Kagan
2019-07-12 13:02 ` Arnd Bergmann
2019-07-12 13:14 ` Paolo Bonzini
2019-07-12 13:32 ` Arnd Bergmann
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