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SubjectRe: [PATCH] KVM: SVM: delay svm_vcpu_init_msrpm after svm->vmcb is initialized
Date
Paolo Bonzini <pbonzini@redhat.com> writes:

> Right now, svm_hv_vmcb_dirty_nested_enlightenments has an incorrect
> dereference of vmcb->control.reserved_sw before the vmcb is checked
> for being non-NULL. The compiler is usually sinking the dereference
> after the check; instead of doing this ourselves in the source,
> ensure that svm_hv_vmcb_dirty_nested_enlightenments is only called
> with a non-NULL VMCB.
>
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> Cc: Vineeth Pillai <viremana@linux.microsoft.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> [Untested for now due to issues with my AMD machine. - Paolo]

At least this doesn't seem to break kvm-amd on bare metal, so

Tested-by: Vitaly Kuznetsov <vkuznets@redhat.com>

> ---
> arch/x86/kvm/svm/svm.c | 4 ++--
> arch/x86/kvm/svm/svm_onhyperv.h | 2 +-
> 2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 9a6987549e1b..4bcb95bb8ed7 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -1406,8 +1406,6 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu)
> goto error_free_vmsa_page;
> }
>
> - svm_vcpu_init_msrpm(vcpu, svm->msrpm);
> -
> svm->vmcb01.ptr = page_address(vmcb01_page);
> svm->vmcb01.pa = __sme_set(page_to_pfn(vmcb01_page) << PAGE_SHIFT);
>
> @@ -1419,6 +1417,8 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu)
> svm_switch_vmcb(svm, &svm->vmcb01);
> init_vmcb(vcpu);
>
> + svm_vcpu_init_msrpm(vcpu, svm->msrpm);
> +
> svm_init_osvw(vcpu);
> vcpu->arch.microcode_version = 0x01000065;
>
> diff --git a/arch/x86/kvm/svm/svm_onhyperv.h b/arch/x86/kvm/svm/svm_onhyperv.h
> index 9b9a55abc29f..c53b8bf8d013 100644
> --- a/arch/x86/kvm/svm/svm_onhyperv.h
> +++ b/arch/x86/kvm/svm/svm_onhyperv.h
> @@ -89,7 +89,7 @@ static inline void svm_hv_vmcb_dirty_nested_enlightenments(
> * as we mark it dirty unconditionally towards end of vcpu
> * init phase.
> */
> - if (vmcb && vmcb_is_clean(vmcb, VMCB_HV_NESTED_ENLIGHTENMENTS) &&
> + if (vmcb_is_clean(vmcb, VMCB_HV_NESTED_ENLIGHTENMENTS) &&
> hve->hv_enlightenments_control.msr_bitmap)
> vmcb_mark_dirty(vmcb, VMCB_HV_NESTED_ENLIGHTENMENTS);
> }

--
Vitaly

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