From: Sean Christopherson <seanjc@google.com>
Date: Fri, 14 Jun 2024 20:28:57 +0000 (+0200)
Subject: KVM: x86: Prevent excluding the BSP on setting max_vcpu_ids
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=d29bf2ca140410705447ac26100a149b51094c00;p=linux.git

KVM: x86: Prevent excluding the BSP on setting max_vcpu_ids

If the BSP vCPU ID was already set, ensure it doesn't get excluded when
limiting vCPU IDs via KVM_CAP_MAX_VCPU_ID.

[mks: provide commit message, code by Sean]

Signed-off-by: Mathias Krause <minipli@grsecurity.net>
Link: https://lore.kernel.org/r/20240614202859.3597745-4-minipli@grsecurity.net
Signed-off-by: Sean Christopherson <seanjc@google.com>
---

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f371943f2c72..994aa281b07d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6707,7 +6707,9 @@ split_irqchip_unlock:
 			break;
 
 		mutex_lock(&kvm->lock);
-		if (kvm->arch.max_vcpu_ids == cap->args[0]) {
+		if (kvm->arch.bsp_vcpu_id > cap->args[0]) {
+			;
+		} else if (kvm->arch.max_vcpu_ids == cap->args[0]) {
 			r = 0;
 		} else if (!kvm->arch.max_vcpu_ids) {
 			kvm->arch.max_vcpu_ids = cap->args[0];