From 14c2bf81fcd2226ca7fb9b179320ca1ca7cb581a Mon Sep 17 00:00:00 2001 From: Wei Huang Date: Tue, 26 Jan 2021 03:18:31 -0500 Subject: [PATCH] KVM: SVM: Fix #GP handling for doubly-nested virtualization 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 Signed-off-by: Bandan Das Signed-off-by: Wei Huang Tested-by: Maxim Levitsky Reviewed-by: Maxim Levitsky Message-Id: <20210126081831.570253-5-wei.huang2@amd.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/svm/svm.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 0378d423044f..8d18f01b29c3 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -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);