[PATCH v3 5/9] KVM: x86: Set kvm_x86_ops only after ->hardware_setup() completes

From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Paul Mackerras <paulus@ozlabs.org>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Janosch Frank <frankja@linux.ibm.com>,
	David Hildenbrand <david@redhat.com>,
	Cornelia Huck <cohuck@redhat.com>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	Marc Zyngier <maz@kernel.org>, James Morse <james.morse@arm.com>,
	Julien Thierry <julien.thierry.kdev@gmail.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	linux-mips@vger.kernel.org, kvm@vger.kernel.org,
	kvm-ppc@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org
Subject: [PATCH v3 5/9] KVM: x86: Set kvm_x86_ops only after ->hardware_setup() completes
Date: Sat, 21 Mar 2020 13:25:59 -0700	[thread overview]
Message-ID: <20200321202603.19355-6-sean.j.christopherson@intel.com> (raw)
In-Reply-To: <20200321202603.19355-1-sean.j.christopherson@intel.com>

Set kvm_x86_ops with the vendor's ops only after ->hardware_setup()
completes to "prevent" using kvm_x86_ops before they are ready, i.e. to
generate a null pointer fault instead of silently consuming unconfigured
state.

An alternative implementation would be to have ->hardware_setup()
return the vendor's ops, but that would require non-trivial refactoring,
and would arguably result in less readable code, e.g. ->hardware_setup()
would need to use ERR_PTR() in multiple locations, and each vendor's
declaration of the runtime ops would be less obvious.

No functional change intended.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 arch/x86/kvm/x86.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 20f989d1bba8..eb1976214ada 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7354,8 +7354,6 @@ int kvm_arch_init(void *opaque)
 	if (r)
 		goto out_free_percpu;
 
-	kvm_x86_ops = ops->runtime_ops;
-
 	kvm_mmu_set_mask_ptes(PT_USER_MASK, PT_ACCESSED_MASK,
 			PT_DIRTY_MASK, PT64_NX_MASK, 0,
 			PT_PRESENT_MASK, 0, sme_me_mask);
@@ -9635,6 +9633,8 @@ int kvm_arch_hardware_setup(void *opaque)
 	if (r != 0)
 		return r;
 
+	kvm_x86_ops = ops->runtime_ops;
+
 	if (!kvm_cpu_cap_has(X86_FEATURE_XSAVES))
 		supported_xss = 0;
 
-- 
2.24.1

