From: Paolo Bonzini <pbonzini@redhat.com>
To: Maxim Levitsky <mlevitsk@redhat.com>, kvm@vger.kernel.org
Cc: Wanpeng Li <wanpengli@tencent.com>,
Borislav Petkov <bp@alien8.de>, Ingo Molnar <mingo@redhat.com>,
"H. Peter Anvin" <hpa@zytor.com>,
linux-kernel@vger.kernel.org,
Sean Christopherson <seanjc@google.com>,
Joerg Roedel <joro@8bytes.org>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>, Vitaly Kuznetsov <vkuznets@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Jim Mattson <jmattson@google.com>
Subject: Re: [PATCH 2/3] KVM: nVMX: restore L1's EFER prior to setting the nested state
Date: Wed, 10 Nov 2021 16:01:49 +0100 [thread overview]
Message-ID: <e6d4e268-da50-c55f-1485-f4a871afdff0@redhat.com> (raw)
In-Reply-To: <20211110100018.367426-3-mlevitsk@redhat.com>
On 11/10/21 11:00, Maxim Levitsky wrote:
> + /*
> + * The vcpu might currently contain L2's IA32_EFER, due to the way
> + * some userspace kvm users (e.g qemu) restore nested state.
> + *
> + * To fix this, restore its IA32_EFER to the value it would have
> + * after VM exit from the nested guest.
> + *
> + */
> +
> + vcpu->arch.efer = nested_vmx_get_vmcs12_host_efer(vcpu, vmcs12);
> +
In principle the value of LOAD_HOST_EFER on exit need not be the same as
on entry. But you don't need all of EFER, only EFER.LME/EFER.LMA, and
those two bits must match ("the values of the LMA and LME bits in the
field must each be that of the “host address-space size” VM-exit
control" from the "Checks on Host Control Registers, MSRs, and SSP";
plus the "Checks Related to Address-Space Size").
At least it's worth adjusting the comment to explain that. But the root
cause of the issue is just nested_vmx_check_* accessing vcpu->arch. So
you can instead:
- split out of nested_vmx_check_host_state a new function
nested_vmx_check_address_state_size that does
#ifdef CONFIG_X86_64
if (CC(!!(vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE) !=
!!(vcpu->arch.efer & EFER_LMA)))
return -EINVAL;
#endif
return 0;
- call it from vmentry but not from migration
- in nested_vmx_check_host_state, assign ia32e from
vmcs12->vm_exit_controls instead of vcpu->arch.efer
Paolo
next prev parent reply other threads:[~2021-11-10 15:02 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-10 10:00 [PATCH 0/3] VMX: nested migration fixes for 32 bit nested guests Maxim Levitsky
2021-11-10 10:00 ` [PATCH 1/3] KVM: nVMX: extract calculation of the L1's EFER Maxim Levitsky
2021-11-10 14:43 ` Vitaly Kuznetsov
2021-11-10 10:00 ` [PATCH 2/3] KVM: nVMX: restore L1's EFER prior to setting the nested state Maxim Levitsky
2021-11-10 15:01 ` Paolo Bonzini [this message]
2021-11-10 15:08 ` Maxim Levitsky
2021-11-10 10:00 ` [PATCH 3/3] KVM: x86/mmu: don't skip mmu initialization when mmu root level changes Maxim Levitsky
2021-11-10 14:48 ` Vitaly Kuznetsov
2021-11-10 15:00 ` Maxim Levitsky
2021-11-10 17:21 ` Sean Christopherson
2021-11-15 12:14 ` Maxim Levitsky
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