Messages in this thread |  | | Date | Sat, 6 Oct 2018 07:08:49 +0000 | From | Wei Yang <> | Subject | Re: [PATCH] kvm/x86 : avoid shifting signed 32-bit value by 31 bits |
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On Sat, Oct 06, 2018 at 11:31:04AM +0800, peng.hao2@zte.com.cn wrote: >>On Thu, Oct 04, 2018 at 01:47:18PM -0400, Peng Hao wrote: >>> >>>From: Peng Hao <peng.hao2@zte.com.cn> >>> >>> modify AVIC_LOGICAL_ID_ENTRY_VALID_MASK to unsigned >>> >>>Signed-off-by: Peng Hao <peng.hao2@zte.com.cn> >>>--- >>> arch/x86/kvm/svm.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>>diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c >>>index d96092b..bf1ded4 100644 >>>--- a/arch/x86/kvm/svm.c >>>+++ b/arch/x86/kvm/svm.c >>>@@ -262,7 +262,7 @@ struct amd_svm_iommu_ir { >>> }; >>> >>> #define AVIC_LOGICAL_ID_ENTRY_GUEST_PHYSICAL_ID_MASK (0xFF) >>>-#define AVIC_LOGICAL_ID_ENTRY_VALID_MASK (1 << 31) >>>+#define AVIC_LOGICAL_ID_ENTRY_VALID_MASK (1UL << 31) > >>It is reasonable to change to unsigned, while not necessary to unsigned >>long? >AVIC_LOGICAL_ID_ENTRY_VALID_MASK is used in function avic_ldr_write. >here I think it doesn't matter if you use unsigned or unsigned long. Do you have any suggestions?
In current case, AVIC_LOGICAL_ID_ENTRY_VALID_MASK is used to calculate the value of new_entry with type of u32. So the definition here is not harmful.
Also, I did a quick grep and found similar definition (1 << 31) is popular in the whole kernel tree.
The reason to make this change is not that strong to me. Would you minding sharing more reason behind this change?
>>-- >>Wei Yang >>Help you, Help me
-- Wei Yang Help you, Help me
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