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KVM: nVMX: Don't speculatively write virtual-APIC page address 

The VIRTUAL_APIC_PAGE_ADDR in vmcs02 is guaranteed to be updated before
it is consumed by hardware, either in nested_vmx_enter_non_root_mode()
or via the KVM_REQ_GET_VMCS12_PAGES callback.  Avoid an extra VMWRITE
and only stuff a bad value into vmcs02 when mapping vmcs12's address
fails.  This also eliminates the need for extra comments to connect the
dots between prepare_vmcs02_early() and nested_get_vmcs12_pages().

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2019-05-07 09:06:33 -07:00 committed by Paolo Bonzini
parent 73cb855684
commit ca2f5466f8
1 changed files with 8 additions and 13 deletions
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21
arch/x86/kvm/vmx/nested.c
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@ -2039,20 +2039,13 @@ static void prepare_vmcs02_early(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12)
exec_control &= ~CPU_BASED_TPR_SHADOW;
exec_control |= vmcs12->cpu_based_vm_exec_control;
/*
* Write an illegal value to VIRTUAL_APIC_PAGE_ADDR. Later, if
* nested_get_vmcs12_pages can't fix it up, the illegal value
* will result in a VM entry failure.
*/
if (exec_control & CPU_BASED_TPR_SHADOW) {
vmcs_write64(VIRTUAL_APIC_PAGE_ADDR, -1ull);
if (exec_control & CPU_BASED_TPR_SHADOW)
vmcs_write32(TPR_THRESHOLD, vmcs12->tpr_threshold);
} else {
#ifdef CONFIG_X86_64
else
exec_control |= CPU_BASED_CR8_LOAD_EXITING |
CPU_BASED_CR8_STORE_EXITING;
#endif
}
/*
* A vmexit (to either L1 hypervisor or L0 userspace) is always needed
@ -2861,10 +2854,6 @@ static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
if (nested_cpu_has(vmcs12, CPU_BASED_TPR_SHADOW)) {
map = &vmx->nested.virtual_apic_map;
/*
* If translation failed, VM entry will fail because
* prepare_vmcs02 set VIRTUAL_APIC_PAGE_ADDR to -1ull.
*/
if (!kvm_vcpu_map(vcpu, gpa_to_gfn(vmcs12->virtual_apic_page_addr), map)) {
vmcs_write64(VIRTUAL_APIC_PAGE_ADDR, pfn_to_hpa(map->pfn));
} else if (nested_cpu_has(vmcs12, CPU_BASED_CR8_LOAD_EXITING) &&
@ -2880,6 +2869,12 @@ static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
*/
vmcs_clear_bits(CPU_BASED_VM_EXEC_CONTROL,
CPU_BASED_TPR_SHADOW);
} else {
/*
* Write an illegal value to VIRTUAL_APIC_PAGE_ADDR to
* force VM-Entry to fail.
*/
vmcs_write64(VIRTUAL_APIC_PAGE_ADDR, -1ull);
}
}