[kvm-unit-tests,PULL,07/12] x86: use a non-negative number in shift
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Message ID 20200616185622.8644-8-thuth@redhat.com
State New
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Series
  • [kvm-unit-tests,PULL,01/12] Fix out-of-tree builds
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Commit Message

Thomas Huth June 16, 2020, 6:56 p.m. UTC
From: Bill Wendling <morbo@google.com>

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>
[thuth: Rebased to master - code is in svm_tests.c instead of svm.c now]
Message-Id: <20200514192626.9950-9-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 x86/svm_tests.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Patch
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diff --git a/x86/svm_tests.c b/x86/svm_tests.c
index c1abd55..a645d66 100644
--- a/x86/svm_tests.c
+++ b/x86/svm_tests.c
@@ -890,7 +890,7 @@  static bool npt_rw_l1mmio_check(struct svm_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 svm_test *test)