linux-kernel - Re: [PATCH] kvm/x86 : avoid shifting signed 32-bit value by 31 bits

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Date:   Sat, 6 Oct 2018 02:11:27 +0000
From:   Wei Yang <richard.weiyang@...il.com>
To:     Peng Hao <penghao122@...a.com.cn>
Cc:     pbonzini@...hat.com, rkrcmar@...hat.com, tglx@...utronix.de,
        mingo@...hat.com, hpa@...or.com, joro@...tes.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org, x86@...nel.org,
        Peng Hao <peng.hao2@....com.cn>
Subject: Re: [PATCH]  kvm/x86 : avoid shifting signed 32-bit value by 31 bits

On Thu, Oct 04, 2018 at 01:47:18PM -0400, Peng Hao wrote:
>
>From: Peng Hao <peng.hao2@....com.cn>
>
>  modify AVIC_LOGICAL_ID_ENTRY_VALID_MASK to unsigned
>
>Signed-off-by: Peng Hao <peng.hao2@....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?

> 
> #define AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK	(0xFFULL)
> #define AVIC_PHYSICAL_ID_ENTRY_BACKING_PAGE_MASK	(0xFFFFFFFFFFULL << 12)
>-- 
>1.8.3.1
>

-- 
Wei Yang
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