From: Maxim Levitsky <mlevitsk@redhat.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>,
kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/7] KVM: nVMX: Release enlightened VMCS on VMCLEAR
Date: Mon, 24 May 2021 15:13:14 +0300 [thread overview]
Message-ID: <779a182e7ed08484658463a69cf3934dcc87464d.camel@redhat.com> (raw)
In-Reply-To: <20210517135054.1914802-3-vkuznets@redhat.com>
On Mon, 2021-05-17 at 15:50 +0200, Vitaly Kuznetsov wrote:
> Unlike VMREAD/VMWRITE/VMPTRLD, VMCLEAR is a valid instruction when
> enlightened VMCS is in use. TLFS has the following brief description:
> "The L1 hypervisor can execute a VMCLEAR instruction to transition an
> enlightened VMCS from the active to the non-active state". Normally,
> this change can be ignored as unmapping active eVMCS can be postponed
> until the next VMLAUNCH instruction but in case nested state is migrated
> with KVM_GET_NESTED_STATE/KVM_SET_NESTED_STATE, keeping eVMCS mapped
> may result in its synchronization with VMCS12 and this is incorrect:
> L1 hypervisor is free to reuse inactive eVMCS memory for something else.
>
> Inactive eVMCS after VMCLEAR can just be unmapped.
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
> arch/x86/kvm/vmx/nested.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 3080e00c8f90..ea2869d8b823 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -5008,6 +5008,8 @@ static int handle_vmclear(struct kvm_vcpu *vcpu)
> vmptr + offsetof(struct vmcs12,
> launch_state),
> &zero, sizeof(zero));
> + } else if (vmx->nested.hv_evmcs && vmptr == vmx->nested.hv_evmcs_vmptr) {
> + nested_release_evmcs(vcpu);
> }
Releasing the eVMCS is a good thing not only for migration
but for instance for nested_vmx_fail which could write to
current eVMCS even outside of nested mode
(there is a bug there but you fixed it in the patch 4).
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Best regards,
Maxim Levitsky
>
> return nested_vmx_succeed(vcpu);
next prev parent reply other threads:[~2021-05-24 12:13 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-17 13:50 [PATCH v2 0/7] KVM: nVMX: Fixes for nested state migration when eVMCS is in use Vitaly Kuznetsov
2021-05-17 13:50 ` [PATCH v2 1/7] KVM: nVMX: Introduce nested_evmcs_is_used() Vitaly Kuznetsov
2021-05-24 12:11 ` Maxim Levitsky
2021-05-24 12:35 ` Vitaly Kuznetsov
2021-05-26 14:34 ` Maxim Levitsky
2021-05-27 7:54 ` Vitaly Kuznetsov
2021-05-27 14:10 ` Maxim Levitsky
2021-05-24 13:54 ` Paolo Bonzini
2021-05-24 14:09 ` Vitaly Kuznetsov
2021-05-24 14:18 ` Paolo Bonzini
2021-05-24 14:37 ` Vitaly Kuznetsov
2021-05-17 13:50 ` [PATCH v2 2/7] KVM: nVMX: Release enlightened VMCS on VMCLEAR Vitaly Kuznetsov
2021-05-24 12:13 ` Maxim Levitsky [this message]
2021-05-17 13:50 ` [PATCH v2 3/7] KVM: nVMX: Ignore 'hv_clean_fields' data when eVMCS data is copied in vmx_get_nested_state() Vitaly Kuznetsov
2021-05-24 12:26 ` Maxim Levitsky
2021-05-24 13:01 ` Vitaly Kuznetsov
2021-05-24 13:58 ` Paolo Bonzini
2021-05-26 14:44 ` Maxim Levitsky
2021-05-24 13:56 ` Paolo Bonzini
2021-05-24 14:12 ` Vitaly Kuznetsov
2021-05-17 13:50 ` [PATCH v2 4/7] KVM: nVMX: Force enlightened VMCS sync from nested_vmx_failValid() Vitaly Kuznetsov
2021-05-24 12:27 ` Maxim Levitsky
2021-05-17 13:50 ` [PATCH v2 5/7] KVM: nVMX: Reset eVMCS clean fields data from prepare_vmcs02() Vitaly Kuznetsov
2021-05-24 12:34 ` Maxim Levitsky
2021-05-24 13:07 ` Vitaly Kuznetsov
2021-05-17 13:50 ` [PATCH v2 6/7] KVM: nVMX: Request to sync eVMCS from VMCS12 after migration Vitaly Kuznetsov
2021-05-24 12:35 ` Maxim Levitsky
2021-05-17 13:50 ` [PATCH v2 7/7] KVM: selftests: evmcs_test: Test that KVM_STATE_NESTED_EVMCS is never lost Vitaly Kuznetsov
2021-05-24 12:36 ` Maxim Levitsky
2021-05-24 12:08 ` [PATCH v2 0/7] KVM: nVMX: Fixes for nested state migration when eVMCS is in use Maxim Levitsky
2021-05-24 12:44 ` Vitaly Kuznetsov
2021-05-26 14:41 ` Maxim Levitsky
2021-05-27 8:01 ` Vitaly Kuznetsov
2021-05-27 14:11 ` Maxim Levitsky
2021-05-27 14:17 ` Paolo Bonzini
2021-05-24 14:01 ` Paolo Bonzini
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