Re: [PATCH v5 7/7] nSVM: use vmcb_ctrl_area_cached instead of vmcb_control_area in struct svm_nested_state

Maxim Levitsky
2021-11-03T17:06:20Z

On Wed, 2021-11-03 at 10:05 -0400, Emanuele Giuseppe Esposito wrote:
> This requires changing all vmcb_is_intercept(&svm->nested.ctl, ...)
> calls with vmcb12_is_intercept().
>
> In addition, in svm_get_nested_state() user space expects a
> vmcb_control_area struct, so we need to copy back all fields
> in a temporary structure to provide to the user space.
>
> Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
> ---
> arch/x86/kvm/svm/nested.c | 48 +++++++++++++++++++++++++--------------
> arch/x86/kvm/svm/svm.c | 4 ++--
> arch/x86/kvm/svm/svm.h | 8 +++----
> 3 files changed, 37 insertions(+), 23 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index cd15d5373c05..6281d1877211 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -58,8 +58,9 @@ static void svm_inject_page_fault_nested(struct kvm_vcpu *vcpu, struct x86_excep
> struct vcpu_svm *svm = to_svm(vcpu);
> WARN_ON(!is_guest_mode(vcpu));
>
> - if (vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_EXCEPTION_OFFSET + PF_VECTOR) &&
> - !svm->nested.nested_run_pending) {
> + if (vmcb12_is_intercept(&svm->nested.ctl,
> + INTERCEPT_EXCEPTION_OFFSET + PF_VECTOR) &&
> + !svm->nested.nested_run_pending) {
> svm->vmcb->control.exit_code = SVM_EXIT_EXCP_BASE + PF_VECTOR;
> svm->vmcb->control.exit_code_hi = 0;
> svm->vmcb->control.exit_info_1 = fault->error_code;
> @@ -121,7 +122,8 @@ static void nested_svm_uninit_mmu_context(struct kvm_vcpu *vcpu)
>
> void recalc_intercepts(struct vcpu_svm *svm)
> {
> - struct vmcb_control_area *c, *h, *g;
> + struct vmcb_control_area *c, *h;
> + struct vmcb_ctrl_area_cached *g;
> unsigned int i;
>
> vmcb_mark_dirty(svm->vmcb, VMCB_INTERCEPTS);
> @@ -172,7 +174,7 @@ static bool nested_svm_vmrun_msrpm(struct vcpu_svm *svm)
> */
> int i;
>
> - if (!(vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_MSR_PROT)))
> + if (!(vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_MSR_PROT)))
> return true;
>
> for (i = 0; i < MSRPM_OFFSETS; i++) {
> @@ -220,9 +222,9 @@ static bool nested_svm_check_tlb_ctl(struct kvm_vcpu *vcpu, u8 tlb_ctl)
> }
>
> static bool nested_vmcb_check_controls(struct kvm_vcpu *vcpu,
> - struct vmcb_control_area *control)
> + struct vmcb_ctrl_area_cached *control)
> {
> - if (CC(!vmcb_is_intercept(control, INTERCEPT_VMRUN)))
> + if (CC(!vmcb12_is_intercept(control, INTERCEPT_VMRUN)))
> return false;
>
> if (CC(control->asid == 0))
> @@ -288,7 +290,7 @@ static bool nested_vmcb_check_save(struct kvm_vcpu *vcpu)
> }
>
> static
> -void _nested_copy_vmcb_control_to_cache(struct vmcb_control_area *to,
> +void _nested_copy_vmcb_control_to_cache(struct vmcb_ctrl_area_cached *to,
> struct vmcb_control_area *from)
> {
> unsigned int i;
> @@ -998,7 +1000,7 @@ static int nested_svm_exit_handled_msr(struct vcpu_svm *svm)
> u32 offset, msr, value;
> int write, mask;
>
> - if (!(vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_MSR_PROT)))
> + if (!(vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_MSR_PROT)))
> return NESTED_EXIT_HOST;
>
> msr = svm->vcpu.arch.regs[VCPU_REGS_RCX];
> @@ -1025,7 +1027,7 @@ static int nested_svm_intercept_ioio(struct vcpu_svm *svm)
> u8 start_bit;
> u64 gpa;
>
> - if (!(vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_IOIO_PROT)))
> + if (!(vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_IOIO_PROT)))
> return NESTED_EXIT_HOST;
>
> port = svm->vmcb->control.exit_info_1 >> 16;
> @@ -1056,12 +1058,12 @@ static int nested_svm_intercept(struct vcpu_svm *svm)
> vmexit = nested_svm_intercept_ioio(svm);
> break;
> case SVM_EXIT_READ_CR0 ... SVM_EXIT_WRITE_CR8: {
> - if (vmcb_is_intercept(&svm->nested.ctl, exit_code))
> + if (vmcb12_is_intercept(&svm->nested.ctl, exit_code))
> vmexit = NESTED_EXIT_DONE;
> break;
> }
> case SVM_EXIT_READ_DR0 ... SVM_EXIT_WRITE_DR7: {
> - if (vmcb_is_intercept(&svm->nested.ctl, exit_code))
> + if (vmcb12_is_intercept(&svm->nested.ctl, exit_code))
> vmexit = NESTED_EXIT_DONE;
> break;
> }
> @@ -1079,7 +1081,7 @@ static int nested_svm_intercept(struct vcpu_svm *svm)
> break;
> }
> default: {
> - if (vmcb_is_intercept(&svm->nested.ctl, exit_code))
> + if (vmcb12_is_intercept(&svm->nested.ctl, exit_code))
> vmexit = NESTED_EXIT_DONE;
> }
> }
> @@ -1157,7 +1159,7 @@ static void nested_svm_inject_exception_vmexit(struct vcpu_svm *svm)
>
> static inline bool nested_exit_on_init(struct vcpu_svm *svm)
> {
> - return vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_INIT);
> + return vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_INIT);
> }
>
> static int svm_check_nested_events(struct kvm_vcpu *vcpu)
> @@ -1300,6 +1302,8 @@ static int svm_get_nested_state(struct kvm_vcpu *vcpu,
> u32 user_data_size)
> {
> struct vcpu_svm *svm;
> + struct vmcb_control_area *ctl;
> + unsigned long r;
> struct kvm_nested_state kvm_state = {
> .flags = 0,
> .format = KVM_STATE_NESTED_FORMAT_SVM,
> @@ -1341,9 +1345,18 @@ static int svm_get_nested_state(struct kvm_vcpu *vcpu,
> */
> if (clear_user(user_vmcb, KVM_STATE_NESTED_SVM_VMCB_SIZE))
> return -EFAULT;
> - if (copy_to_user(&user_vmcb->control, &svm->nested.ctl,
> - sizeof(user_vmcb->control)))
> +
> + ctl = kzalloc(sizeof(*ctl), GFP_KERNEL);
> + if (!ctl)
> + return -ENOMEM;
> +
> + nested_copy_vmcb_cache_to_control(ctl, &svm->nested.ctl);
> + r = copy_to_user(&user_vmcb->control, ctl,
> + sizeof(user_vmcb->control));
> + kfree(ctl);
> + if (r)
> return -EFAULT;
> +
> if (copy_to_user(&user_vmcb->save, &svm->vmcb01.ptr->save,
> sizeof(user_vmcb->save)))
> return -EFAULT;
> @@ -1361,6 +1374,7 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
> struct vmcb_control_area *ctl;
> struct vmcb_save_area *save;
> struct vmcb_save_area_cached save_cached;
> + struct vmcb_ctrl_area_cached ctl_cached;
> unsigned long cr0;
> int ret;
>
> @@ -1413,7 +1427,8 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
> goto out_free;
>
> ret = -EINVAL;
> - if (!nested_vmcb_check_controls(vcpu, ctl))
> + _nested_copy_vmcb_control_to_cache(&ctl_cached, ctl);
> + if (!nested_vmcb_check_controls(vcpu, &ctl_cached))
> goto out_free;
>
> /*
> @@ -1470,7 +1485,6 @@ static int svm_set_nested_state(struct kvm_vcpu *vcpu,
> svm->nested.vmcb12_gpa = kvm_state->hdr.svm.vmcb_pa;
>
> svm_copy_vmrun_state(&svm->vmcb01.ptr->save, save);
> - nested_copy_vmcb_control_to_cache(svm, ctl);
You should keep this line of code, to actualy load the control area,

The whole copying to 'cache' is a bit ugly here, but let it be,
as there is no other way around and the uglyness is only limited to those two functions
(svm_get_nested_state/svm_set_nested_state).

I am currently testing your patches with the above change reverted.
Seems to pass at least my basic test so far.

Thanks,
Best regards,
Maxim Levitsky

>
> svm_switch_vmcb(svm, &svm->nested.vmcb02);
> nested_vmcb02_prepare_control(svm);
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 74d6db9017ea..134205678462 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -2506,7 +2506,7 @@ static bool check_selective_cr0_intercepted(struct kvm_vcpu *vcpu,
> bool ret = false;
>
> if (!is_guest_mode(vcpu) ||
> - (!(vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_SELECTIVE_CR0))))
> + (!(vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_SELECTIVE_CR0))))
> return false;
>
> cr0 &= ~SVM_CR0_SELECTIVE_MASK;
> @@ -4218,7 +4218,7 @@ static int svm_check_intercept(struct kvm_vcpu *vcpu,
> info->intercept == x86_intercept_clts)
> break;
>
> - if (!(vmcb_is_intercept(&svm->nested.ctl,
> + if (!(vmcb12_is_intercept(&svm->nested.ctl,
> INTERCEPT_SELECTIVE_CR0)))
> break;
>
> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> index e29423d4337c..a896a52417ee 100644
> --- a/arch/x86/kvm/svm/svm.h
> +++ b/arch/x86/kvm/svm/svm.h
> @@ -156,7 +156,7 @@ struct svm_nested_state {
> bool nested_run_pending;
>
> /* cache for control fields of the guest */
> - struct vmcb_control_area ctl;
> + struct vmcb_ctrl_area_cached ctl;
> struct vmcb_save_area_cached save;
>
> bool initialized;
> @@ -494,17 +494,17 @@ static inline bool nested_svm_virtualize_tpr(struct kvm_vcpu *vcpu)
>
> static inline bool nested_exit_on_smi(struct vcpu_svm *svm)
> {
> - return vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_SMI);
> + return vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_SMI);
> }
>
> static inline bool nested_exit_on_intr(struct vcpu_svm *svm)
> {
> - return vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_INTR);
> + return vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_INTR);
> }
>
> static inline bool nested_exit_on_nmi(struct vcpu_svm *svm)
> {
> - return vmcb_is_intercept(&svm->nested.ctl, INTERCEPT_NMI);
> + return vmcb12_is_intercept(&svm->nested.ctl, INTERCEPT_NMI);
> }
>
> int enter_svm_guest_mode(struct kvm_vcpu *vcpu,