linux-kernel - [PATCH v2 2/2] x86/kvm: handle the failure of __pv_cpu

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Date:   Tue, 10 May 2022 19:38:30 -0700
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 v2 2/2] x86/kvm: handle the failure of __pv_cpu_mask allocation

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

Fallback to native ipis/tlb flush if fails to allocate __pv_cpu_mask.

Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
---
v1 -> v2:
 * move orig_apic under CONFIG_SMP

 arch/x86/kernel/kvm.c | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 8b1c45c9cda8..ce03121d038b 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -457,6 +457,7 @@ static int kvm_cpu_online(unsigned int cpu)
 
 #ifdef CONFIG_SMP
 
+static struct apic orig_apic;
 static DEFINE_PER_CPU(cpumask_var_t, __pv_cpu_mask);
 
 static bool pv_tlb_flush_supported(void)
@@ -543,6 +544,11 @@ static void __send_ipi_mask(const struct cpumask *mask, int vector)
 
 static void kvm_send_ipi_mask(const struct cpumask *mask, int vector)
 {
+	if (unlikely(!this_cpu_cpumask_var_ptr(__pv_cpu_mask))) {
+		orig_apic.send_IPI_mask(mask, vector);
+		return;
+	}
+
 	__send_ipi_mask(mask, vector);
 }
 
@@ -552,6 +558,11 @@ static void kvm_send_ipi_mask_allbutself(const struct cpumask *mask, int vector)
 	struct cpumask *new_mask = this_cpu_cpumask_var_ptr(__pv_cpu_mask);
 	const struct cpumask *local_mask;
 
+	if (unlikely(!new_mask)) {
+		orig_apic.send_IPI_mask_allbutself(mask, vector);
+		return;
+	}
+
 	cpumask_copy(new_mask, mask);
 	cpumask_clear_cpu(this_cpu, new_mask);
 	local_mask = new_mask;
@@ -612,6 +623,7 @@ late_initcall(setup_efi_kvm_sev_migration);
  */
 static void kvm_setup_pv_ipi(void)
 {
+	orig_apic = *apic;
 	apic->send_IPI_mask = kvm_send_ipi_mask;
 	apic->send_IPI_mask_allbutself = kvm_send_ipi_mask_allbutself;
 	pr_info("setup PV IPIs\n");
@@ -640,6 +652,11 @@ static void kvm_flush_tlb_multi(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_multi(cpumask, info);
+		return;
+	}
+
 	cpumask_copy(flushmask, cpumask);
 	/*
 	 * We have to call flush only on online vCPUs. And
@@ -672,11 +689,16 @@ static __init int kvm_alloc_cpumask(void)
 
 	if (pv_tlb_flush_supported() || pv_ipi_supported())
 		for_each_possible_cpu(cpu) {
-			zalloc_cpumask_var_node(per_cpu_ptr(&__pv_cpu_mask, cpu),
-				GFP_KERNEL, cpu_to_node(cpu));
+			if (!zalloc_cpumask_var_node(&per_cpu(__pv_cpu_mask, cpu),
+				GFP_KERNEL, cpu_to_node(cpu)))
+				goto err_out;
 		}
 
 	return 0;
+err_out:
+	for_each_possible_cpu(cpu)
+		free_cpumask_var(per_cpu(__pv_cpu_mask, cpu));
+	return -ENOMEM;
 }
 arch_initcall(kvm_alloc_cpumask);
 
-- 
2.25.1