KVM: VMX: Use vmx to inject real-mode interrupts

Instead of injecting real-mode interrupts by writing the interrupt frame into
guest memory, abuse vmx by injecting a software interrupt.  We need to
pretend the software interrupt instruction had a length > 0, so we have to
adjust rip backward.

This lets us not to mess with writing guest memory, which is complex and also
sleeps.

Signed-off-by: Avi Kivity <avi@qumranet.com>

2 files changed, 5 insertions, 49 deletions

diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c
index eca422e9506d..d2c25e25d3aa 100644
--- a/drivers/kvm/vmx.c
+++ b/drivers/kvm/vmx.c
@@ -1709,58 +1709,13 @@ out:
         return ret;
 }
 
-static void inject_rmode_irq(struct kvm_vcpu *vcpu, int irq)
-{
-        u16 ent[2];
-        u16 cs;
-        u16 ip;
-        unsigned long flags;
-        unsigned long ss_base = vmcs_readl(GUEST_SS_BASE);
-        u16 sp =  vmcs_readl(GUEST_RSP);
-        u32 ss_limit = vmcs_read32(GUEST_SS_LIMIT);
-
-        if (sp > ss_limit || sp < 6) {
-                vcpu_printf(vcpu, "%s: #SS, rsp 0x%lx ss 0x%lx limit 0x%x\n",
-                            __FUNCTION__,
-                            vmcs_readl(GUEST_RSP),
-                            vmcs_readl(GUEST_SS_BASE),
-                            vmcs_read32(GUEST_SS_LIMIT));
-                return;
-        }
-
-        if (emulator_read_std(irq * sizeof(ent), &ent, sizeof(ent), vcpu) !=
-                                                        X86EMUL_CONTINUE) {
-                vcpu_printf(vcpu, "%s: read guest err\n", __FUNCTION__);
-                return;
-        }
-
-        flags =  vmcs_readl(GUEST_RFLAGS);
-        cs =  vmcs_readl(GUEST_CS_BASE) >> 4;
-        ip =  vmcs_readl(GUEST_RIP);
-
-
-        if (emulator_write_emulated(
-                    ss_base + sp - 2, &flags, 2, vcpu) != X86EMUL_CONTINUE ||
-            emulator_write_emulated(
-                    ss_base + sp - 4, &cs, 2, vcpu) != X86EMUL_CONTINUE ||
-            emulator_write_emulated(
-                    ss_base + sp - 6, &ip, 2, vcpu) != X86EMUL_CONTINUE) {
-                vcpu_printf(vcpu, "%s: write guest err\n", __FUNCTION__);
-                return;
-        }
-
-        vmcs_writel(GUEST_RFLAGS, flags &
-                    ~(X86_EFLAGS_IF | X86_EFLAGS_AC | X86_EFLAGS_TF));
-        vmcs_write16(GUEST_CS_SELECTOR, ent[1]) ;
-        vmcs_writel(GUEST_CS_BASE, ent[1] << 4);
-        vmcs_writel(GUEST_RIP, ent[0]);
-        vmcs_writel(GUEST_RSP, (vmcs_readl(GUEST_RSP) & ~0xffff) | (sp - 6));
-}
-
 static void vmx_inject_irq(struct kvm_vcpu *vcpu, int irq)
 {
         if (vcpu->rmode.active) {
-                inject_rmode_irq(vcpu, irq);
+                vmcs_write32(VM_ENTRY_INTR_INFO_FIELD,
+                             irq | INTR_TYPE_SOFT_INTR | INTR_INFO_VALID_MASK);
+                vmcs_write32(VM_ENTRY_INSTRUCTION_LEN, 1);
+                vmcs_writel(GUEST_RIP, vmcs_readl(GUEST_RIP) - 1);
                 return;
         }
         vmcs_write32(VM_ENTRY_INTR_INFO_FIELD,
diff --git a/drivers/kvm/vmx.h b/drivers/kvm/vmx.h
index c84bd3733153..d757b36c2fbe 100644
--- a/drivers/kvm/vmx.h
+++ b/drivers/kvm/vmx.h
@@ -233,6 +233,7 @@ enum vmcs_field {
 
 #define INTR_TYPE_EXT_INTR              (0 << 8) /* external interrupt */
 #define INTR_TYPE_EXCEPTION             (3 << 8) /* processor exception */
+#define INTR_TYPE_SOFT_INTR             (4 << 8) /* software interrupt */
 
 /*
  * Exit Qualifications for MOV for Control Register Access