KVM: x86/xen: intercept xen hypercalls if enabled

Add a new exit reason for emulator to handle Xen hypercalls.

Since this means KVM owns the ABI, dispense with the facility for the
VMM to provide its own copy of the hypercall pages; just fill them in
directly using VMCALL/VMMCALL as we do for the Hyper-V hypercall page.

This behaviour is enabled by a new INTERCEPT_HCALL flag in the
KVM_XEN_HVM_CONFIG ioctl structure, and advertised by the same flag
being returned from the KVM_CAP_XEN_HVM check.

Rename xen_hvm_config() to kvm_xen_write_hypercall_page() and move it
to the nascent xen.c while we're at it, and add a test case.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>

1 files changed, 20 insertions, 0 deletions

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index dfe3ba5cf262..c87defe5db4f 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -216,6 +216,20 @@ struct kvm_hyperv_exit {
 	} u;
 };
 
+struct kvm_xen_exit {
+#define KVM_EXIT_XEN_HCALL          1
+	__u32 type;
+	union {
+		struct {
+			__u32 longmode;
+			__u32 cpl;
+			__u64 input;
+			__u64 result;
+			__u64 params[6];
+		} hcall;
+	} u;
+};
+
 #define KVM_S390_GET_SKEYS_NONE   1
 #define KVM_S390_SKEYS_MAX        1048576
 
@@ -253,6 +267,7 @@ struct kvm_hyperv_exit {
 #define KVM_EXIT_DIRTY_RING_FULL  31
 #define KVM_EXIT_AP_RESET_HOLD    32
 #define KVM_EXIT_X86_BUS_LOCK     33
+#define KVM_EXIT_XEN              34
 
 /* For KVM_EXIT_INTERNAL_ERROR */
 /* Emulate instruction failed. */
@@ -429,6 +444,8 @@ struct kvm_run {
 			__u32 index; /* kernel -> user */
 			__u64 data; /* kernel <-> user */
 		} msr;
+		/* KVM_EXIT_XEN */
+		struct kvm_xen_exit xen;
 		/* Fix the size of the union. */
 		char padding[256];
 	};
@@ -1133,6 +1150,9 @@ struct kvm_x86_mce {
 #endif
 
 #ifdef KVM_CAP_XEN_HVM
+#define KVM_XEN_HVM_CONFIG_HYPERCALL_MSR	(1 << 0)
+#define KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL	(1 << 1)
+
 struct kvm_xen_hvm_config {
 	__u32 flags;
 	__u32 msr;