linux-kernel - [PATCH] Revert "KVM: Check the allocation of pv cpu mask"

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Date:   Wed, 16 Sep 2020 11:03:42 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Haiwei Li <lihaiwei@...cent.com>, linux-kernel@...r.kernel.org,
        x86@...nel.org
Subject: [PATCH] Revert "KVM: Check the allocation of pv cpu mask"

The commit 0f990222108d ("KVM: Check the allocation of pv cpu mask") we
have in 5.9-rc5 has two issue:
1) Compilation fails for !CONFIG_SMP, see:
   https://bugzilla.kernel.org/show_bug.cgi?id=209285

2) This commit completely disables PV TLB flush, see
   https://lore.kernel.org/kvm/87y2lrnnyf.fsf@vitty.brq.redhat.com/

The allocation problem is likely a theoretical one, if we don't
have memory that early in boot process we're likely doomed anyway.
Let's solve it properly later.

This reverts commit 0f990222108d214a0924d920e6095b58107d7b59.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kernel/kvm.c | 22 +++-------------------
 1 file changed, 3 insertions(+), 19 deletions(-)

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 1b51b727b140..9663ba31347c 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -652,6 +652,7 @@ 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");
 	}
@@ -764,14 +765,6 @@ static __init int activate_jump_labels(void)
 }
 arch_initcall(activate_jump_labels);
 
-static void kvm_free_pv_cpu_mask(void)
-{
-	unsigned int cpu;
-
-	for_each_possible_cpu(cpu)
-		free_cpumask_var(per_cpu(__pv_cpu_mask, cpu));
-}
-
 static __init int kvm_alloc_cpumask(void)
 {
 	int cpu;
@@ -790,20 +783,11 @@ static __init int kvm_alloc_cpumask(void)
 
 	if (alloc)
 		for_each_possible_cpu(cpu) {
-			if (!zalloc_cpumask_var_node(
-				per_cpu_ptr(&__pv_cpu_mask, cpu),
-				GFP_KERNEL, cpu_to_node(cpu))) {
-				goto zalloc_cpumask_fail;
-			}
+			zalloc_cpumask_var_node(per_cpu_ptr(&__pv_cpu_mask, cpu),
+				GFP_KERNEL, cpu_to_node(cpu));
 		}
 
-	apic->send_IPI_mask_allbutself = kvm_send_ipi_mask_allbutself;
-	pv_ops.mmu.flush_tlb_others = kvm_flush_tlb_others;
 	return 0;
-
-zalloc_cpumask_fail:
-	kvm_free_pv_cpu_mask();
-	return -ENOMEM;
 }
 arch_initcall(kvm_alloc_cpumask);
 
-- 
2.25.4