linux-kernel - [PATCH 2/2] KVM: Check if __pv_cpu_mask was allocated instead of assigning ops too late

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Date:   Mon, 14 Sep 2020 17:11:48 +0800
From:   lihaiwei.kernel@...il.com
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org, x86@...nel.org
Cc:     pbonzini@...hat.com, sean.j.christopherson@...el.com,
        vkuznets@...hat.com, wanpengli@...cent.com, jmattson@...gle.com,
        joro@...tes.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, hpa@...or.com, lihaiwei@...cent.com
Subject: [PATCH 2/2] KVM: Check if __pv_cpu_mask was allocated instead of assigning ops too late

From: Haiwei Li <lihaiwei@...cent.com>

Without this patch, kvm_flush_tlb_others is not called. We can always check
if __pv_cpu_mask was allocated and revert back to the architectural path if
not.

Suggested-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Signed-off-by: Haiwei Li <lihaiwei@...cent.com>
---
 arch/x86/kernel/kvm.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 7e8be0421720..3c6c516d9828 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -553,7 +553,6 @@ static void kvm_send_ipi_mask_allbutself(const struct cpumask *mask, int vector)
 static void kvm_setup_pv_ipi(void)
 {
 	apic->send_IPI_mask = kvm_send_ipi_mask;
-	apic->send_IPI_mask_allbutself = kvm_send_ipi_mask_allbutself;
 	pr_info("setup PV IPIs\n");
 }
 
@@ -619,6 +618,11 @@ static void kvm_flush_tlb_others(const struct cpumask *cpumask,
 	struct kvm_steal_time *src;
 	struct cpumask *flushmask = this_cpu_cpumask_var_ptr(__pv_cpu_mask);
 
+	if (unlikely(!flushmask)) {
+		native_flush_tlb_others(cpumask, info);
+		return;
+	}
+
 	cpumask_copy(flushmask, cpumask);
 	/*
 	 * We have to call flush only on online vCPUs. And
@@ -652,6 +656,7 @@ static void __init kvm_guest_init(void)
 	}
 
 	if (pv_tlb_flush_supported()) {
+		pv_ops.mmu.flush_tlb_others = kvm_flush_tlb_others;
 		pv_ops.mmu.tlb_remove_table = tlb_remove_table;
 		pr_info("KVM setup pv remote TLB flush\n");
 	}
@@ -800,7 +805,6 @@ static __init int kvm_alloc_cpumask(void)
 #if defined(CONFIG_SMP)
 	apic->send_IPI_mask_allbutself = kvm_send_ipi_mask_allbutself;
 #endif
-	pv_ops.mmu.flush_tlb_others = kvm_flush_tlb_others;
 	return 0;
 
 zalloc_cpumask_fail:
-- 
2.18.4