linux-kernel - [PATCH] x86/kvm: Don't waste memory if kvmclock is disabled

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Date:   Tue, 22 Feb 2022 01:02:03 -0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>
Subject: [PATCH] x86/kvm: Don't waste memory if kvmclock is disabled

From: Wanpeng Li <wanpengli@...cent.com>

Even if "no-kvmclock" is passed in cmdline parameter, the guest kernel 
still allocates hvclock_mem which is scaled by the number of vCPUs, 
let's check kvmclock enable in advance to avoid this memory waste.

Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
---
 arch/x86/kernel/kvmclock.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index a35cbf9107af..44ed677d401f 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -239,6 +239,9 @@ static void __init kvmclock_init_mem(void)
 
 static int __init kvm_setup_vsyscall_timeinfo(void)
 {
+	if (!kvmclock)
+		return 0;
+
 	kvmclock_init_mem();
 
 #ifdef CONFIG_X86_64
-- 
2.25.1