Date:   Wed, 30 Oct 2019 14:04:18 -0700
In-Reply-To: <20191030210419.213407-1-morbo@google.com>
Message-Id: <20191030210419.213407-6-morbo@google.com>
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References: <20191015000411.59740-1-morbo@google.com> <20191030210419.213407-1-morbo@google.com>
Subject: [kvm-unit-tests PATCH v3 5/6] x86: use a non-negative number in shift
From:   Bill Wendling <morbo@google.com>
To:     kvm@vger.kernel.org, pbonzini@redhat.com, thuth@redhat.com
Cc:     jmattson@google.com, sean.j.christopherson@intel.com,
        Bill Wendling <morbo@google.com>
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Sender: kvm-owner@vger.kernel.org
Precedence: bulk

Shifting a negative number is undefined. Clang complains about it:

x86/svm.c:1131:38: error: shifting a negative signed value is undefined [-Werror,-Wshift-negative-value]
    test->vmcb->control.tsc_offset = TSC_OFFSET_VALUE;

Using "~0ull" results in identical asm code:

	before: movabsq $-281474976710656, %rsi
	after:  movabsq $-281474976710656, %rsi

Signed-off-by: Bill Wendling <morbo@google.com>
---
 x86/svm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/x86/svm.c b/x86/svm.c
index 4ddfaa4..cef43d5 100644
--- a/x86/svm.c
+++ b/x86/svm.c
@@ -1122,7 +1122,7 @@ static bool npt_rw_l1mmio_check(struct test *test)
 }
 
 #define TSC_ADJUST_VALUE    (1ll << 32)
-#define TSC_OFFSET_VALUE    (-1ll << 48)
+#define TSC_OFFSET_VALUE    (~0ull << 48)
 static bool ok;
 
 static void tsc_adjust_prepare(struct test *test)
-- 
2.24.0.rc1.363.gb1bccd3e3d-goog