Re: [PATCH 8/9] Add VMEXIT handler and intercepts v2

Joerg Roedel
2008-09-10T19:12:11Z

On Fri, Sep 05, 2008 at 09:51:23AM +0200, Alexander Graf wrote:
> This adds the #VMEXIT intercept, so we return to the level 1 guest
> when something happens in the level 2 guest that should return to
> the level 1 guest.
>
> v2 implements HIF handling and cleans up exception interception
>
> Signed-off-by: Alexander Graf <agraf@suse.de>
> ---
> arch/x86/kvm/svm.c | 319 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 319 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index c47f039..8318a63 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -74,6 +74,13 @@ module_param(npt, int, S_IRUGO);
> static void kvm_reput_irq(struct vcpu_svm *svm);
> static void svm_flush_tlb(struct kvm_vcpu *vcpu);
>
> +static int nested_svm_exit_handled(struct vcpu_svm *svm, bool kvm_override);
> +static int nested_svm_vmexit(struct vcpu_svm *svm);
> +static int nested_svm_vmsave(struct vcpu_svm *svm, void *nested_vmcb,
> + void *arg2, void *opaque);
> +static int nested_svm_check_exception(struct vcpu_svm *svm, unsigned nr,
> + bool has_error_code, u32 error_code);
> +
> static inline struct vcpu_svm *to_svm(struct kvm_vcpu *vcpu)
> {
> return container_of(vcpu, struct vcpu_svm, vcpu);
> @@ -223,6 +230,11 @@ static void svm_queue_exception(struct kvm_vcpu *vcpu, unsigned nr,
> {
> struct vcpu_svm *svm = to_svm(vcpu);
>
> + /* If we are within a nested VM we'd better #VMEXIT and let the
> + guest handle the exception */
> + if (nested_svm_check_exception(svm, nr, has_error_code, error_code))
> + return;
> +
> svm->vmcb->control.event_inj = nr
> | SVM_EVTINJ_VALID
> | (has_error_code ? SVM_EVTINJ_VALID_ERR : 0)
> @@ -1185,6 +1197,43 @@ static int vmmcall_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run)
> return 1;
> }
>
> +static int nested_svm_check_exception(struct vcpu_svm *svm, unsigned nr,
> + bool has_error_code, u32 error_code)
> +{
> + if (is_nested(svm)) {
> + svm->vmcb->control.exit_code = SVM_EXIT_EXCP_BASE + nr;
> + svm->vmcb->control.exit_code_hi = 0;
> + svm->vmcb->control.exit_info_1 = error_code;
> + svm->vmcb->control.exit_info_2 = svm->vcpu.arch.cr2;
> + if (nested_svm_exit_handled(svm, false)) {
> + nsvm_printk("VMexit -> EXCP 0x%x\n", nr);
> +
> + nested_svm_vmexit(svm);
> + return 1;
> + }
> + }
> +
> + return 0;
> +}
> +
> +static inline int nested_svm_intr(struct vcpu_svm *svm)
> +{
> + if (is_nested(svm)) {
> + if (!(svm->vcpu.arch.hflags & HF_HIF_MASK))

HF_HIF_MASK?
Do you really need to check GIF if the vcpu is in guest mode? The guest
itself can't influence the GIF so it should always be set.

> + return 0;
> +
> + svm->vmcb->control.exit_code = SVM_EXIT_INTR;
> +
> + if (nested_svm_exit_handled(svm, false)) {
> + nsvm_printk("VMexit -> INTR\n");
> + nested_svm_vmexit(svm);
> + return 1;
> + }

The VMEXIT is only required if the guest vmcb has set V_INTR_MASKING.
Otherwise we can inject the interrupt directly into the l2 guest. This
is no problem for running KVM-in-KVM because KVM always sets
V_INTR_MASKING. But to keep the implementation close to real hardware
behavior this bit should be checked.

> + }
> +
> + return 0;
> +}
> +
> static struct page *nested_svm_get_page(struct vcpu_svm *svm, u64 gpa)
> {
> struct page *page;
> @@ -1251,6 +1300,257 @@ static int nested_svm_do(struct vcpu_svm *svm,
> return retval;
> }
>
> +static int nested_svm_exit_handled_real(struct vcpu_svm *svm,
> + void *arg1,
> + void *arg2,
> + void *opaque)
> +{
> + struct vmcb *nested_vmcb = (struct vmcb *)arg1;
> + bool kvm_overrides = *(bool *)opaque;
> + u32 exit_code = svm->vmcb->control.exit_code;
> +
> + if (kvm_overrides) {
> + switch (exit_code) {
> + case SVM_EXIT_INTR:
> + case SVM_EXIT_NMI:
> + return 0;
> + /* For now we are always handling NPFs when using them */
> + case SVM_EXIT_NPF:
> + if (npt_enabled)
> + return 0;
> + break;
> + /* When we're shadowing, trap PFs */
> + case SVM_EXIT_EXCP_BASE + PF_VECTOR:
> + if (!npt_enabled)
> + return 0;
> + break;
> + default:
> + break;
> + }
> + }
> +
> + switch (exit_code) {
> + case SVM_EXIT_READ_CR0 ... SVM_EXIT_READ_CR8: {
> + u32 cr_bits = 1 << (exit_code - SVM_EXIT_READ_CR0);
> + if (nested_vmcb->control.intercept_cr_read & cr_bits)
> + return 1;
> + break;
> + }
> + case SVM_EXIT_WRITE_CR0 ... SVM_EXIT_WRITE_CR8: {
> + u32 cr_bits = 1 << (exit_code - SVM_EXIT_WRITE_CR0);
> + if (nested_vmcb->control.intercept_cr_write & cr_bits)
> + return 1;
> + break;
> + }
> + case SVM_EXIT_READ_DR0 ... SVM_EXIT_READ_DR7: {
> + u32 dr_bits = 1 << (exit_code - SVM_EXIT_READ_DR0);
> + if (nested_vmcb->control.intercept_dr_read & dr_bits)
> + return 1;
> + break;
> + }
> + case SVM_EXIT_WRITE_DR0 ... SVM_EXIT_WRITE_DR7: {
> + u32 dr_bits = 1 << (exit_code - SVM_EXIT_WRITE_DR0);
> + if (nested_vmcb->control.intercept_dr_write & dr_bits)
> + return 1;
> + break;
> + }
> + case SVM_EXIT_EXCP_BASE ... SVM_EXIT_EXCP_BASE + 0x1f: {
> + u32 excp_bits = 1 << (exit_code - SVM_EXIT_EXCP_BASE);
> + if (nested_vmcb->control.intercept_exceptions & excp_bits)
> + return 1;
> + break;
> + }
> + default: {
> + u64 exit_bits = 1ULL << (exit_code - SVM_EXIT_INTR);
> + nsvm_printk("exit code: 0x%x\n", exit_code);
> + if (nested_vmcb->control.intercept & exit_bits)
> + return 1;
> + }
> + }
> +
> + return 0;
> +}
> +
> +#ifdef NESTED_KVM_MERGE_IOPM
> +static int nested_svm_exit_handled_io(struct vcpu_svm *svm,
> + void *arg1, void *arg2,
> + void *opaque)
> +{
> + struct vmcb *nested_vmcb = (struct vmcb *)arg1;
> + u16 param = (u16)(svm->vmcb->control.exit_info_1);
> + u16 port = (u16)(svm->vmcb->control.exit_info_1 >> 16);
> + u16 mask = (1 << ((param >> 4) & 7)) - 1;
> + u8 *iopm = (u8 *)arg2 + (port / 8);
> + u16 iopmw = iopm[0] | (iopm[1] << 8);
> +
> + if (!(nested_vmcb->control.intercept & (1ULL << INTERCEPT_IOIO_PROT)))
> + return 0;
> + if (iopmw & (mask << (port & 7)))
> + return 1;
> +
> + nsvm_printk("nKVM: No IO-Intercept on param=0x%hx port=0x%hx "
> + "mask=0x%hx iopm=0x%hx\n", param, port, mask, iopmw);
> +
> + return 0;
> +}
> +#endif
> +
> +static int nested_svm_exit_handled_msr(struct vcpu_svm *svm,
> + void *arg1, void *arg2,
> + void *opaque)
> +{
> + struct vmcb *nested_vmcb = (struct vmcb *)arg1;
> + u8 *msrpm = (u8 *)arg2;
> + u32 t0, t1;
> + u32 msr = svm->vcpu.arch.regs[VCPU_REGS_RCX];
> + u32 param = svm->vmcb->control.exit_info_1 & 1;
> +
> + if (!(nested_vmcb->control.intercept & (1ULL << INTERCEPT_MSR_PROT)))
> + return 0;
> +
> + switch(msr) {
> + case 0 ... 0x1fff:
> + t0 = (msr * 2) % 8;
> + t1 = msr / 8;
> + break;
> + case 0xc0000000 ... 0xc0001fff:
> + t0 = (8192 + msr - 0xc0000000) * 2;
> + t1 = (t0 / 8);
> + t0 %= 8;
> + break;
> + case 0xc0010000 ... 0xc0011fff:
> + t0 = (16384 + msr - 0xc0010000) * 2;
> + t1 = (t0 / 8);
> + t0 %= 8;
> + break;
> + default:
> + return 1;
> + break;
> + }
> + if (msrpm[t1] & ((1 << param) << t0))
> + return 1;
> +
> + return 0;
> +}
> +
> +static int nested_svm_exit_handled(struct vcpu_svm *svm, bool kvm_override)
> +{
> + bool k = kvm_override;
> +
> + switch (svm->vmcb->control.exit_code) {
> +#ifdef NESTED_KVM_MERGE_IOPM
> + case SVM_EXIT_IOIO:
> + return nested_svm_do(svm, svm->nested_vmcb,
> + svm->nested_vmcb_iopm, NULL,
> + nested_svm_exit_handled_io);
> + break;
> +#endif
> + case SVM_EXIT_MSR:
> + return nested_svm_do(svm, svm->nested_vmcb,
> + svm->nested_vmcb_msrpm, NULL,
> + nested_svm_exit_handled_msr);
> + default: break;
> + }
> +
> + return nested_svm_do(svm, svm->nested_vmcb, 0, &k,
> + nested_svm_exit_handled_real);
> +}
> +
> +static int nested_svm_vmexit_real(struct vcpu_svm *svm, void *arg1,
> + void *arg2, void *opaque)
> +{
> + struct vmcb *nested_vmcb = (struct vmcb *)arg1;
> + struct vmcb *hsave = (struct vmcb *)arg2;
> + u64 nested_save[] = { nested_vmcb->save.cr0,
> + nested_vmcb->save.cr3,
> + nested_vmcb->save.cr4,
> + nested_vmcb->save.efer,
> + nested_vmcb->control.intercept_cr_read,
> + nested_vmcb->control.intercept_cr_write,
> + nested_vmcb->control.intercept_dr_read,
> + nested_vmcb->control.intercept_dr_write,
> + nested_vmcb->control.intercept_exceptions,
> + nested_vmcb->control.intercept,
> + nested_vmcb->control.msrpm_base_pa,
> + nested_vmcb->control.iopm_base_pa,
> + nested_vmcb->control.tsc_offset };
> +
> + /* Give the current vmcb to the guest */
> + memcpy(nested_vmcb, svm->vmcb, sizeof(struct vmcb));
> + nested_vmcb->save.cr0 = nested_save[0];
> + if (!npt_enabled)
> + nested_vmcb->save.cr3 = nested_save[1];
> + nested_vmcb->save.cr4 = nested_save[2];
> + nested_vmcb->save.efer = nested_save[3];
> + nested_vmcb->control.intercept_cr_read = nested_save[4];
> + nested_vmcb->control.intercept_cr_write = nested_save[5];
> + nested_vmcb->control.intercept_dr_read = nested_save[6];
> + nested_vmcb->control.intercept_dr_write = nested_save[7];
> + nested_vmcb->control.intercept_exceptions = nested_save[8];
> + nested_vmcb->control.intercept = nested_save[9];
> + nested_vmcb->control.msrpm_base_pa = nested_save[10];
> + nested_vmcb->control.iopm_base_pa = nested_save[11];
> + nested_vmcb->control.tsc_offset = nested_save[12];
> +
> + if ((nested_vmcb->control.int_ctl & V_IRQ_MASK) &&
> + (nested_vmcb->control.int_vector)) {
> + nsvm_printk("WARNING: IRQ 0x%x still enabled on #VMEXIT\n",
> + nested_vmcb->control.int_vector);
> + }
> +
> + /* Restore the original control entries */
> + svm->vmcb->control = hsave->control;
> +
> + /* Flush the virtual TLB */
> + force_new_asid(&svm->vcpu);
> +
> + /* Kill any pending exceptions */
> + if (svm->vcpu.arch.exception.pending == true)
> + nsvm_printk("WARNING: Pending Exception\n");
> + svm->vcpu.arch.exception.pending = false;
> +
> + /* Restore selected save entries */
> + svm->vmcb->save.es = hsave->save.es;
> + svm->vmcb->save.cs = hsave->save.cs;
> + svm->vmcb->save.ss = hsave->save.ss;
> + svm->vmcb->save.ds = hsave->save.ds;
> + svm->vmcb->save.gdtr = hsave->save.gdtr;
> + svm->vmcb->save.idtr = hsave->save.idtr;
> + svm->vmcb->save.rflags = hsave->save.rflags;
> + svm_set_efer(&svm->vcpu, hsave->save.efer);
> + svm_set_cr0(&svm->vcpu, hsave->save.cr0 | X86_CR0_PE);
> + svm_set_cr4(&svm->vcpu, hsave->save.cr4);
> + if (npt_enabled) {
> + svm->vmcb->save.cr3 = hsave->save.cr3;
> + svm->vcpu.arch.cr3 = hsave->save.cr3;
> + } else {
> + kvm_set_cr3(&svm->vcpu, hsave->save.cr3);
> + }
> + kvm_mmu_reset_context(&svm->vcpu);
> + kvm_mmu_load(&svm->vcpu);
> + kvm_register_write(&svm->vcpu, VCPU_REGS_RAX, hsave->save.rax);
> + kvm_register_write(&svm->vcpu, VCPU_REGS_RSP, hsave->save.rsp);
> + kvm_register_write(&svm->vcpu, VCPU_REGS_RIP, hsave->save.rip);
> + svm->vmcb->save.dr7 = 0;
> + svm->vmcb->save.cpl = 0;
> + svm->vmcb->control.exit_int_info = 0;
> +
> + svm->vcpu.arch.hflags &= ~HF_GIF_MASK;
> + /* Exit nested SVM mode */
> + svm->nested_vmcb = 0;
> +
> + return 0;
> +}
> +
> +static int nested_svm_vmexit(struct vcpu_svm *svm)
> +{
> + nsvm_printk("VMexit\n");
> + if (nested_svm_do(svm, svm->nested_vmcb, svm->nested_hsave,
> + NULL, nested_svm_vmexit_real))
> + return 1;
> +
> + return 0;
> +}
>
> static int nested_svm_vmrun_msrpm(struct vcpu_svm *svm, void *arg1,
> void *arg2, void *opaque)
> @@ -1831,6 +2131,17 @@ static int handle_exit(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
> KVMTRACE_3D(VMEXIT, vcpu, exit_code, (u32)svm->vmcb->save.rip,
> (u32)((u64)svm->vmcb->save.rip >> 32), entryexit);
>
> + if (is_nested(svm)) {
> + nsvm_printk("nested handle_exit: 0x%x | 0x%lx | 0x%lx | 0x%lx\n",
> + exit_code, svm->vmcb->control.exit_info_1,
> + svm->vmcb->control.exit_info_2, svm->vmcb->save.rip);
> + if (nested_svm_exit_handled(svm, true)) {
> + nested_svm_vmexit(svm);
> + nsvm_printk("-> #VMEXIT\n");
> + return 1;
> + }
> + }
> +
> if (npt_enabled) {
> int mmu_reload = 0;
> if ((vcpu->arch.cr0 ^ svm->vmcb->save.cr0) & X86_CR0_PG) {
> @@ -1917,6 +2228,8 @@ static void svm_set_irq(struct kvm_vcpu *vcpu, int irq)
> {
> struct vcpu_svm *svm = to_svm(vcpu);
>
> + nested_svm_intr(svm);
> +
> svm_inject_irq(svm, irq);
> }
>
> @@ -1962,6 +2275,9 @@ static void svm_intr_assist(struct kvm_vcpu *vcpu)
> if (!kvm_cpu_has_interrupt(vcpu))
> goto out;
>
> + if (nested_svm_intr(svm))
> + goto out;
> +
> if (!(svm->vcpu.arch.hflags & HF_GIF_MASK))
> goto out;
>
> @@ -2014,6 +2330,9 @@ static void do_interrupt_requests(struct kvm_vcpu *vcpu,
> struct vcpu_svm *svm = to_svm(vcpu);
> struct vmcb_control_area *control = &svm->vmcb->control;
>
> + if (nested_svm_intr(svm))
> + return;
> +
> svm->vcpu.arch.interrupt_window_open =
> (!(control->int_state & SVM_INTERRUPT_SHADOW_MASK) &&
> (svm->vmcb->save.rflags & X86_EFLAGS_IF) &&
> --
> 1.5.6