linux-kernel - [PATCH] KVM: x86: Use div64_ul instead of do

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Message-Id: <20211217084155.452262-1-deng.changcheng@zte.com.cn>
Date:   Fri, 17 Dec 2021 08:41:55 +0000
From:   cgel.zte@...il.com
To:     pbonzini@...hat.com
Cc:     seanjc@...gle.com, vkuznets@...hat.com, wanpengli@...cent.com,
        jmattson@...gle.com, joro@...tes.org, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        x86@...nel.org, hpa@...or.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Changcheng Deng <deng.changcheng@....com.cn>,
        Zeal Robot <zealci@....com.cn>
Subject: [PATCH] KVM: x86: Use div64_ul instead of do_div

From: Changcheng Deng <deng.changcheng@....com.cn>

do_div() does a 64-by-32 division. Here the divisor is an unsigned long
which on some platforms is 64 bit wide. So use div64_ul instead of do_div
to avoid a possible truncation.

Reported-by: Zeal Robot <zealci@....com.cn>
Signed-off-by: Changcheng Deng <deng.changcheng@....com.cn>
---
 arch/x86/kvm/lapic.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index c5028e6b0f96..3b629870632c 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1707,7 +1707,7 @@ static void start_sw_tscdeadline(struct kvm_lapic *apic)
 	guest_tsc = kvm_read_l1_tsc(vcpu, rdtsc());
 
 	ns = (tscdeadline - guest_tsc) * 1000000ULL;
-	do_div(ns, this_tsc_khz);
+	ns = div64_ul(ns, this_tsc_khz);
 
 	if (likely(tscdeadline > guest_tsc) &&
 	    likely(ns > apic->lapic_timer.timer_advance_ns)) {
-- 
2.25.1