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KVM: SVM: Fix #GP handling for doubly-nested virtualization

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Under the case of nested on nested (L0, L1, L2 are all hypervisors),
we do not support emulation of the vVMLOAD/VMSAVE feature, the
L0 hypervisor can inject the proper #VMEXIT to inform L1 of what is
happening and L1 can avoid invoking the #GP workaround.  For this
reason we turns on guest VM's X86_FEATURE_SVME_ADDR_CHK bit for KVM
running inside VM to receive the notification and change behavior.

Similarly we check if vcpu is under guest mode before emulating the
vmware-backdoor instructions. For the case of nested on nested, we
let the guest handle it.

Co-developed-by: Bandan Das <bsd@redhat.com>
Signed-off-by: Bandan Das <bsd@redhat.com>
Signed-off-by: Wei Huang <wei.huang2@amd.com>
Tested-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210126081831.570253-5-wei.huang2@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Wei Huang 2021-01-26 03:18:31 -05:00 committed by Paolo Bonzini
parent 3b9c723ed7
commit 14c2bf81fc
1 changed files with 18 additions and 2 deletions
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20
arch/x86/kvm/svm/svm.c
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@ -933,6 +933,9 @@ static __init void svm_set_cpu_caps(void)
if (npt_enabled)
kvm_cpu_cap_set(X86_FEATURE_NPT);
/* Nested VM can receive #VMEXIT instead of triggering #GP */
kvm_cpu_cap_set(X86_FEATURE_SVME_ADDR_CHK);
}
/* CPUID 0x80000008 */
@ -2202,6 +2205,11 @@ static int svm_instr_opcode(struct kvm_vcpu *vcpu)
static int emulate_svm_instr(struct kvm_vcpu *vcpu, int opcode)
{
const int guest_mode_exit_codes[] = {
[SVM_INSTR_VMRUN] = SVM_EXIT_VMRUN,
[SVM_INSTR_VMLOAD] = SVM_EXIT_VMLOAD,
[SVM_INSTR_VMSAVE] = SVM_EXIT_VMSAVE,
};
int (*const svm_instr_handlers[])(struct vcpu_svm *svm) = {
[SVM_INSTR_VMRUN] = vmrun_interception,
[SVM_INSTR_VMLOAD] = vmload_interception,
@ -2209,7 +2217,14 @@ static int emulate_svm_instr(struct kvm_vcpu *vcpu, int opcode)
};
struct vcpu_svm *svm = to_svm(vcpu);
return svm_instr_handlers[opcode](svm);
if (is_guest_mode(vcpu)) {
svm->vmcb->control.exit_code = guest_mode_exit_codes[opcode];
svm->vmcb->control.exit_info_1 = 0;
svm->vmcb->control.exit_info_2 = 0;
return nested_svm_vmexit(svm);
} else
return svm_instr_handlers[opcode](svm);
}
/*
@ -2244,7 +2259,8 @@ static int gp_interception(struct vcpu_svm *svm)
* VMware backdoor emulation on #GP interception only handles
* IN{S}, OUT{S}, and RDPMC.
*/
return kvm_emulate_instruction(vcpu,
if (!is_guest_mode(vcpu))
return kvm_emulate_instruction(vcpu,
EMULTYPE_VMWARE_GP | EMULTYPE_NO_DECODE);
} else
return emulate_svm_instr(vcpu, opcode);