[RFC PATCH 22/73] KVM: x86/PVM: Handle some VM exits before enable interrupts

Lai Jiangshan
2024-02-26T14:35:50Z

Similar to VMX, NMI should be handled in non-instrumented code early
after VM exit. Additionally, #PF, #VE, #VC, and #DB need early handling
in non-instrumented code as well. Host interrupts and #MC need to be
handled before enabling interrupts.

Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
---
arch/x86/kvm/pvm/pvm.c | 89 ++++++++++++++++++++++++++++++++++++++++++
arch/x86/kvm/pvm/pvm.h | 8 ++++
2 files changed, 97 insertions(+)

diff --git a/arch/x86/kvm/pvm/pvm.c b/arch/x86/kvm/pvm/pvm.c
index 00a50ed0c118..29c6d8da7c19 100644
--- a/arch/x86/kvm/pvm/pvm.c
+++ b/arch/x86/kvm/pvm/pvm.c
@@ -265,6 +265,58 @@ static void pvm_setup_mce(struct kvm_vcpu *vcpu)
{
}

+static int handle_exit_external_interrupt(struct kvm_vcpu *vcpu)
+{
+ ++vcpu->stat.irq_exits;
+ return 1;
+}
+
+static int handle_exit_failed_vmentry(struct kvm_vcpu *vcpu)
+{
+ struct vcpu_pvm *pvm = to_pvm(vcpu);
+ u32 error_code = pvm->exit_error_code;
+
+ kvm_queue_exception_e(vcpu, GP_VECTOR, error_code);
+ return 1;
+}
+
+/*
+ * The guest has exited. See if we can fix it or if we need userspace
+ * assistance.
+ */
+static int pvm_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
+{
+ struct vcpu_pvm *pvm = to_pvm(vcpu);
+ u32 exit_reason = pvm->exit_vector;
+
+ if (exit_reason >= FIRST_EXTERNAL_VECTOR && exit_reason < NR_VECTORS)
+ return handle_exit_external_interrupt(vcpu);
+ else if (exit_reason == PVM_FAILED_VMENTRY_VECTOR)
+ return handle_exit_failed_vmentry(vcpu);
+
+ vcpu_unimpl(vcpu, "pvm: unexpected exit reason 0x%x\n", exit_reason);
+ vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+ vcpu->run->internal.suberror =
+ KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON;
+ vcpu->run->internal.ndata = 2;
+ vcpu->run->internal.data[0] = exit_reason;
+ vcpu->run->internal.data[1] = vcpu->arch.last_vmentry_cpu;
+ return 0;
+}
+
+static void pvm_handle_exit_irqoff(struct kvm_vcpu *vcpu)
+{
+ struct vcpu_pvm *pvm = to_pvm(vcpu);
+ u32 vector = pvm->exit_vector;
+ gate_desc *desc = (gate_desc *)host_idt_base + vector;
+
+ if (vector >= FIRST_EXTERNAL_VECTOR && vector < NR_VECTORS &&
+ vector != IA32_SYSCALL_VECTOR)
+ kvm_do_interrupt_irqoff(vcpu, gate_offset(desc));
+ else if (vector == MC_VECTOR)
+ kvm_machine_check();
+}
+
static bool pvm_has_emulated_msr(struct kvm *kvm, u32 index)
{
switch (index) {
@@ -369,6 +421,40 @@ static noinstr void pvm_vcpu_run_noinstr(struct kvm_vcpu *vcpu)
pvm->exit_vector = (ret_regs->orig_ax >> 32);
pvm->exit_error_code = (u32)ret_regs->orig_ax;

+ // handle noinstr vmexits reasons.
+ switch (pvm->exit_vector) {
+ case PF_VECTOR:
+ // if the exit due to #PF, check for async #PF.
+ pvm->exit_cr2 = read_cr2();
+ vcpu->arch.apf.host_apf_flags = kvm_read_and_reset_apf_flags();
+ break;
+ case NMI_VECTOR:
+ kvm_do_nmi_irqoff(vcpu);
+ break;
+ case VE_VECTOR:
+ // TODO: pvm host is TDX guest.
+ // tdx_get_ve_info(&pvm->host_ve);
+ break;
+ case X86_TRAP_VC:
+ /*
+ * TODO: pvm host is SEV guest.
+ * if (!vc_is_db(error_code)) {
+ * collect info and handle the first part for #VC
+ * break;
+ * } else {
+ * get_debugreg(pvm->exit_dr6, 6);
+ * set_debugreg(DR6_RESERVED, 6);
+ * }
+ */
+ break;
+ case DB_VECTOR:
+ get_debugreg(pvm->exit_dr6, 6);
+ set_debugreg(DR6_RESERVED, 6);
+ break;
+ default:
+ break;
+ }
+
guest_state_exit_irqoff();
}

@@ -682,9 +768,12 @@ static struct kvm_x86_ops pvm_x86_ops __initdata = {

.vcpu_pre_run = pvm_vcpu_pre_run,
.vcpu_run = pvm_vcpu_run,
+ .handle_exit = pvm_handle_exit,

.vcpu_after_set_cpuid = pvm_vcpu_after_set_cpuid,

+ .handle_exit_irqoff = pvm_handle_exit_irqoff,
+
.sched_in = pvm_sched_in,

.nested_ops = &pvm_nested_ops,
diff --git a/arch/x86/kvm/pvm/pvm.h b/arch/x86/kvm/pvm/pvm.h
index 349f4eac98ec..123cfe1c3c6a 100644
--- a/arch/x86/kvm/pvm/pvm.h
+++ b/arch/x86/kvm/pvm/pvm.h
@@ -7,6 +7,8 @@

#define SWITCH_FLAGS_INIT (SWITCH_FLAGS_SMOD)

+#define PVM_FAILED_VMENTRY_VECTOR SWITCH_EXIT_REASONS_FAILED_VMETNRY
+
#define PT_L4_SHIFT 39
#define PT_L4_SIZE (1UL << PT_L4_SHIFT)
#define DEFAULT_RANGE_L4_SIZE (32 * PT_L4_SIZE)
@@ -35,6 +37,12 @@ struct vcpu_pvm {

u16 host_ds_sel, host_es_sel;

+ union {
+ unsigned long exit_extra;
+ unsigned long exit_cr2;
+ unsigned long exit_dr6;
+ struct ve_info exit_ve;
+ };
u32 exit_vector;
u32 exit_error_code;
u32 hw_cs, hw_ss;
--
2.19.1.6.gb485710b