KVM: add MSR based hypercall API
This adds a special MSR based hypercall API to KVM. This is to be
used by paravirtual kernels and virtual drivers.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Avi Kivity <avi@qumranet.com>
diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 122c05f..757a41f 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -1204,6 +1204,73 @@
}
}
+/*
+ * Register the para guest with the host:
+ */
+static int vcpu_register_para(struct kvm_vcpu *vcpu, gpa_t para_state_gpa)
+{
+ struct kvm_vcpu_para_state *para_state;
+ hpa_t para_state_hpa, hypercall_hpa;
+ struct page *para_state_page;
+ unsigned char *hypercall;
+ gpa_t hypercall_gpa;
+
+ printk(KERN_DEBUG "kvm: guest trying to enter paravirtual mode\n");
+ printk(KERN_DEBUG ".... para_state_gpa: %08Lx\n", para_state_gpa);
+
+ /*
+ * Needs to be page aligned:
+ */
+ if (para_state_gpa != PAGE_ALIGN(para_state_gpa))
+ goto err_gp;
+
+ para_state_hpa = gpa_to_hpa(vcpu, para_state_gpa);
+ printk(KERN_DEBUG ".... para_state_hpa: %08Lx\n", para_state_hpa);
+ if (is_error_hpa(para_state_hpa))
+ goto err_gp;
+
+ para_state_page = pfn_to_page(para_state_hpa >> PAGE_SHIFT);
+ para_state = kmap_atomic(para_state_page, KM_USER0);
+
+ printk(KERN_DEBUG ".... guest version: %d\n", para_state->guest_version);
+ printk(KERN_DEBUG ".... size: %d\n", para_state->size);
+
+ para_state->host_version = KVM_PARA_API_VERSION;
+ /*
+ * We cannot support guests that try to register themselves
+ * with a newer API version than the host supports:
+ */
+ if (para_state->guest_version > KVM_PARA_API_VERSION) {
+ para_state->ret = -KVM_EINVAL;
+ goto err_kunmap_skip;
+ }
+
+ hypercall_gpa = para_state->hypercall_gpa;
+ hypercall_hpa = gpa_to_hpa(vcpu, hypercall_gpa);
+ printk(KERN_DEBUG ".... hypercall_hpa: %08Lx\n", hypercall_hpa);
+ if (is_error_hpa(hypercall_hpa)) {
+ para_state->ret = -KVM_EINVAL;
+ goto err_kunmap_skip;
+ }
+
+ printk(KERN_DEBUG "kvm: para guest successfully registered.\n");
+ vcpu->para_state_page = para_state_page;
+ vcpu->para_state_gpa = para_state_gpa;
+ vcpu->hypercall_gpa = hypercall_gpa;
+
+ hypercall = kmap_atomic(pfn_to_page(hypercall_hpa >> PAGE_SHIFT),
+ KM_USER1) + (hypercall_hpa & ~PAGE_MASK);
+ kvm_arch_ops->patch_hypercall(vcpu, hypercall);
+ kunmap_atomic(hypercall, KM_USER1);
+
+ para_state->ret = 0;
+err_kunmap_skip:
+ kunmap_atomic(para_state, KM_USER0);
+ return 0;
+err_gp:
+ return 1;
+}
+
int kvm_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
{
u64 data;
@@ -1312,6 +1379,12 @@
case MSR_IA32_MISC_ENABLE:
vcpu->ia32_misc_enable_msr = data;
break;
+ /*
+ * This is the 'probe whether the host is KVM' logic:
+ */
+ case MSR_KVM_API_MAGIC:
+ return vcpu_register_para(vcpu, data);
+
default:
printk(KERN_ERR "kvm: unhandled wrmsr: 0x%x\n", msr);
return 1;