KVM: VMX: Enable acknowledge interupt on vmexit
The "acknowledge interrupt on exit" feature controls processor behavior
for external interrupt acknowledgement. When this control is set, the
processor acknowledges the interrupt controller to acquire the
interrupt vector on VM exit.
After enabling this feature, an interrupt which arrived when target cpu is
running in vmx non-root mode will be handled by vmx handler instead of handler
in idt. Currently, vmx handler only fakes an interrupt stack and jump to idt
table to let real handler to handle it. Further, we will recognize the interrupt
and only delivery the interrupt which not belong to current vcpu through idt table.
The interrupt which belonged to current vcpu will be handled inside vmx handler.
This will reduce the interrupt handle cost of KVM.
Also, interrupt enable logic is changed if this feature is turnning on:
Before this patch, hypervior call local_irq_enable() to enable it directly.
Now IF bit is set on interrupt stack frame, and will be enabled on a return from
interrupt handler if exterrupt interrupt exists. If no external interrupt, still
call local_irq_enable() to enable it.
Refer to Intel SDM volum 3, chapter 33.2.
Signed-off-by: Yang Zhang <yang.z.zhang@Intel.com>
Reviewed-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 7175557..7a7605f 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -378,6 +378,7 @@
struct shared_msr_entry *guest_msrs;
int nmsrs;
int save_nmsrs;
+ unsigned long host_idt_base;
#ifdef CONFIG_X86_64
u64 msr_host_kernel_gs_base;
u64 msr_guest_kernel_gs_base;
@@ -2627,7 +2628,8 @@
#ifdef CONFIG_X86_64
min |= VM_EXIT_HOST_ADDR_SPACE_SIZE;
#endif
- opt = VM_EXIT_SAVE_IA32_PAT | VM_EXIT_LOAD_IA32_PAT;
+ opt = VM_EXIT_SAVE_IA32_PAT | VM_EXIT_LOAD_IA32_PAT |
+ VM_EXIT_ACK_INTR_ON_EXIT;
if (adjust_vmx_controls(min, opt, MSR_IA32_VMX_EXIT_CTLS,
&_vmexit_control) < 0)
return -EIO;
@@ -3879,7 +3881,7 @@
* Note that host-state that does change is set elsewhere. E.g., host-state
* that is set differently for each CPU is set in vmx_vcpu_load(), not here.
*/
-static void vmx_set_constant_host_state(void)
+static void vmx_set_constant_host_state(struct vcpu_vmx *vmx)
{
u32 low32, high32;
unsigned long tmpl;
@@ -3907,6 +3909,7 @@
native_store_idt(&dt);
vmcs_writel(HOST_IDTR_BASE, dt.address); /* 22.2.4 */
+ vmx->host_idt_base = dt.address;
vmcs_writel(HOST_RIP, vmx_return); /* 22.2.5 */
@@ -4039,7 +4042,7 @@
vmcs_write16(HOST_FS_SELECTOR, 0); /* 22.2.4 */
vmcs_write16(HOST_GS_SELECTOR, 0); /* 22.2.4 */
- vmx_set_constant_host_state();
+ vmx_set_constant_host_state(vmx);
#ifdef CONFIG_X86_64
rdmsrl(MSR_FS_BASE, a);
vmcs_writel(HOST_FS_BASE, a); /* 22.2.4 */
@@ -6399,6 +6402,52 @@
}
}
+static void vmx_handle_external_intr(struct kvm_vcpu *vcpu)
+{
+ u32 exit_intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
+
+ /*
+ * If external interrupt exists, IF bit is set in rflags/eflags on the
+ * interrupt stack frame, and interrupt will be enabled on a return
+ * from interrupt handler.
+ */
+ if ((exit_intr_info & (INTR_INFO_VALID_MASK | INTR_INFO_INTR_TYPE_MASK))
+ == (INTR_INFO_VALID_MASK | INTR_TYPE_EXT_INTR)) {
+ unsigned int vector;
+ unsigned long entry;
+ gate_desc *desc;
+ struct vcpu_vmx *vmx = to_vmx(vcpu);
+#ifdef CONFIG_X86_64
+ unsigned long tmp;
+#endif
+
+ vector = exit_intr_info & INTR_INFO_VECTOR_MASK;
+ desc = (gate_desc *)vmx->host_idt_base + vector;
+ entry = gate_offset(*desc);
+ asm volatile(
+#ifdef CONFIG_X86_64
+ "mov %%" _ASM_SP ", %[sp]\n\t"
+ "and $0xfffffffffffffff0, %%" _ASM_SP "\n\t"
+ "push $%c[ss]\n\t"
+ "push %[sp]\n\t"
+#endif
+ "pushf\n\t"
+ "orl $0x200, (%%" _ASM_SP ")\n\t"
+ __ASM_SIZE(push) " $%c[cs]\n\t"
+ "call *%[entry]\n\t"
+ :
+#ifdef CONFIG_X86_64
+ [sp]"=&r"(tmp)
+#endif
+ :
+ [entry]"r"(entry),
+ [ss]"i"(__KERNEL_DS),
+ [cs]"i"(__KERNEL_CS)
+ );
+ } else
+ local_irq_enable();
+}
+
static void vmx_recover_nmi_blocking(struct vcpu_vmx *vmx)
{
u32 exit_intr_info;
@@ -7041,7 +7090,7 @@
* Other fields are different per CPU, and will be set later when
* vmx_vcpu_load() is called, and when vmx_save_host_state() is called.
*/
- vmx_set_constant_host_state();
+ vmx_set_constant_host_state(vmx);
/*
* HOST_RSP is normally set correctly in vmx_vcpu_run() just before
@@ -7718,6 +7767,7 @@
.set_tdp_cr3 = vmx_set_cr3,
.check_intercept = vmx_check_intercept,
+ .handle_external_intr = vmx_handle_external_intr,
};
static int __init vmx_init(void)