Re: [PATCH v2 09/46] KVM: SVM: Drop a redundant init_vmcb() from svm_create_vcpu()

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On 13/07/21 18:32, Sean Christopherson wrote:
Drop an extra init_vmcb() from svm_create_vcpu(), svm_vcpu_reset() is
guaranteed to call init_vmcb() and there are no consumers of the VMCB
data between ->vcpu_create() and ->vcpu_reset().  Keep the call to
svm_switch_vmcb() as sev_es_create_vcpu() touches the current VMCB, but
hoist it up a few lines to associate the switch with the allocation of
vmcb01.

Reviewed-by: Reiji Watanabe <reijiw@xxxxxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
  arch/x86/kvm/svm/svm.c | 4 +---
  1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 44248548be7d..cef9520fe77f 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1431,15 +1431,13 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu)
svm->vmcb01.ptr = page_address(vmcb01_page);
  	svm->vmcb01.pa = __sme_set(page_to_pfn(vmcb01_page) << PAGE_SHIFT);
+	svm_switch_vmcb(svm, &svm->vmcb01);
if (vmsa_page)
  		svm->vmsa = page_address(vmsa_page);
svm->guest_state_loaded = false; - svm_switch_vmcb(svm, &svm->vmcb01);
-	init_vmcb(vcpu);
-
  	svm_init_osvw(vcpu);
  	vcpu->arch.microcode_version = 0x01000065;

While this patch makes sense, I'd rather not include it to reduce the part of the code in which svm->vmcb is NULL. See for example the issue reported by the static analyzer in which svm_hv_vmcb_dirty_nested_enlightenments (called by svm_vcpu_init_msrpm) dereferences svm->vmcb.

Paolo




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