xen/privcmd: implement the dm op ioctl

Use an interface compatible with the Linux one so that the user-space
libraries already using the Linux interface can be used without much
modifications.

This allows user-space to make use of the dm_op family of hypercalls,
which are used by device models.

Sponsored by:	Citrix Systems R&D

sys/amd64/include/xen/hypercall.h

@@ -427,6 +427,13 @@ HYPERVISOR_kexec_op(
 	return _hypercall2(int, kexec_op, op, args);
 }
 
+static inline int __must_check
+HYPERVISOR_dm_op(
+	domid_t domid, unsigned int nr_bufs, const void *bufs)
+{
+	return _hypercall3(int, dm_op, domid, nr_bufs, bufs);
+}
+
 #undef __must_check
 
 #endif /* __MACHINE_XEN_HYPERCALL_H__ */

sys/dev/xen/privcmd/privcmd.c

@@ -65,6 +65,8 @@ __FBSDID("$FreeBSD$");
 
 MALLOC_DEFINE(M_PRIVCMD, "privcmd_dev", "Xen privcmd user-space device");
 
+#define MAX_DMOP_BUFFERS 16
+
 struct privcmd_map {
 	vm_object_t mem;
 	vm_size_t size;
@@ -423,6 +425,53 @@ privcmd_ioctl(struct cdev *dev, unsigned long cmd, caddr_t arg,
 		if (!umap->mapped)
 			free(umap->err, M_PRIVCMD);
 
+		break;
+	}
+	case IOCTL_PRIVCMD_DM_OP: {
+		const struct ioctl_privcmd_dmop *dmop;
+		struct privcmd_dmop_buf *bufs;
+		struct xen_dm_op_buf *hbufs;
+
+		dmop = (struct ioctl_privcmd_dmop *)arg;
+
+		if (dmop->num == 0)
+			break;
+
+		if (dmop->num > MAX_DMOP_BUFFERS) {
+			error = E2BIG;
+			break;
+		}
+
+		bufs = malloc(sizeof(*bufs) * dmop->num, M_PRIVCMD, M_WAITOK);
+
+		error = copyin(dmop->ubufs, bufs, sizeof(*bufs) * dmop->num);
+		if (error != 0) {
+			free(bufs, M_PRIVCMD);
+			break;
+		}
+
+		hbufs = malloc(sizeof(*hbufs) * dmop->num, M_PRIVCMD, M_WAITOK);
+		for (i = 0; i < dmop->num; i++) {
+			set_xen_guest_handle(hbufs[i].h, bufs[i].uptr);
+			hbufs[i].size = bufs[i].size;
+		}
+
+#ifdef __amd64__
+		if (cpu_stdext_feature & CPUID_STDEXT_SMAP)
+			stac();
+#endif
+		error = HYPERVISOR_dm_op(dmop->dom, dmop->num, hbufs);
+#ifdef __amd64__
+		if (cpu_stdext_feature & CPUID_STDEXT_SMAP)
+			clac();
+#endif
+		if (error != 0)
+			error = xen_translate_error(error);
+
+		free(bufs, M_PRIVCMD);
+		free(hbufs, M_PRIVCMD);
+
+
 		break;
 	}
 	default:

sys/i386/include/xen/hypercall.h

@@ -404,6 +404,13 @@ HYPERVISOR_kexec_op(
 {
         return _hypercall2(int, kexec_op, op, args);
 }
+
+static inline int
+HYPERVISOR_dm_op(
+	domid_t domid, unsigned int nr_bufs, const void *bufs)
+{
+	return _hypercall3(int, dm_op, domid, nr_bufs, bufs);
+}
 #endif /* __HYPERCALL_H__ */
 
 /*

sys/xen/hypervisor.h

@@ -20,6 +20,7 @@
 #include <xen/interface/sched.h>
 #include <xen/interface/callback.h>
 #include <xen/interface/memory.h>
+#include <xen/interface/hvm/dm_op.h>
 #include <machine/xen/hypercall.h>
 
 extern uint64_t get_system_time(int ticks);

sys/xen/privcmd.h

@@ -63,11 +63,24 @@ struct ioctl_privcmd_mmapresource {
 	 */
 };
 
+struct privcmd_dmop_buf {
+	void *uptr; /* pointer to memory (in calling process) */
+	size_t size; /* size of the buffer */
+};
+
+struct ioctl_privcmd_dmop {
+	domid_t dom; /* target domain */
+	unsigned int num; /* num of buffers */
+	const struct privcmd_dmop_buf *ubufs; /* array of buffers */
+};
+
 #define IOCTL_PRIVCMD_HYPERCALL					\
 	_IOWR('E', 0, struct ioctl_privcmd_hypercall)
 #define IOCTL_PRIVCMD_MMAPBATCH					\
 	_IOWR('E', 1, struct ioctl_privcmd_mmapbatch)
 #define IOCTL_PRIVCMD_MMAP_RESOURCE				\
 	_IOW('E', 2, struct ioctl_privcmd_mmapresource)
+#define IOCTL_PRIVCMD_DM_OP					\
+	_IOW('E', 3, struct ioctl_privcmd_dmop)
 
 #endif /* !__XEN_PRIVCMD_H__ */