linux-kernel - [PATCH 2/2] KVM: x86: Defer "already loaded" check until after basic support checks

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Date:   Mon, 18 Oct 2021 11:39:29 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     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>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Paul Menzel <pmenzel@...gen.mpg.de>,
        "Maciej S . Szmigiero" <mail@...iej.szmigiero.name>
Subject: [PATCH 2/2] KVM: x86: Defer "already loaded" check until after basic
 support checks

Move KVM's check for a vendor module already being loaded below the basic
functionality checks so that attempting to load an unsupported module
provides the same result regardless of whether or not a supported vendor
module is already loaded.

Intentionally keep the err non-ratelimited; if userspace is probing two
different modules for the same vendor on all CPUs, it deserves the spam.

Reported-by: Paul Menzel <pmenzel@...gen.mpg.de>
Cc: Maciej S. Szmigiero <mail@...iej.szmigiero.name>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/x86.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e966e9cdd805..f67da77be267 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8538,12 +8538,6 @@ int kvm_arch_init(void *opaque)
 	struct kvm_x86_init_ops *ops = opaque;
 	int r;
 
-	if (kvm_x86_ops.hardware_enable) {
-		pr_err("kvm: already loaded vendor module '%s'\n", kvm_x86_ops.name);
-		r = -EEXIST;
-		goto out;
-	}
-
 	if (!ops->cpu_has_kvm_support()) {
 		pr_err_ratelimited("kvm: no hardware support for '%s'\n",
 				   ops->runtime_ops->name);
@@ -8556,6 +8550,11 @@ int kvm_arch_init(void *opaque)
 		r = -EOPNOTSUPP;
 		goto out;
 	}
+	if (kvm_x86_ops.hardware_enable) {
+		pr_err("kvm: already loaded vendor module '%s'\n", kvm_x86_ops.name);
+		r = -EEXIST;
+		goto out;
+	}
 
 	/*
 	 * KVM explicitly assumes that the guest has an FPU and
-- 
2.33.0.1079.g6e70778dc9-goog