[xen] Add basic support for PV-HVM domains

Add basic support for Xen PV-HVM domains (detected via the Xen
platform PCI device with IDs 5853:0001), including support for
accessing configuration via XenStore and enumerating devices via
XenBus.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

5 files changed, 762 insertions, 0 deletions

diff --git a/src/arch/x86/Makefile b/src/arch/x86/Makefile
index cdd397d4..e555587d 100644
--- a/src/arch/x86/Makefile
+++ b/src/arch/x86/Makefile
@@ -8,6 +8,7 @@ SRCDIRS		+= arch/x86/core
 SRCDIRS		+= arch/x86/interface/efi
 SRCDIRS		+= arch/x86/prefix
 SRCDIRS		+= arch/x86/hci/commands
+SRCDIRS		+= arch/x86/drivers/xen
 
 # breaks building some of the linux-related objects
 CFLAGS		+= -Ulinux
diff --git a/src/arch/x86/drivers/xen/hvm.c b/src/arch/x86/drivers/xen/hvm.c
new file mode 100644
index 00000000..fbbcdf02
--- /dev/null
+++ b/src/arch/x86/drivers/xen/hvm.c
@@ -0,0 +1,521 @@
+/*
+ * Copyright (C) 2014 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <stdint.h>
+#include <stdio.h>
+#include <errno.h>
+#include <ipxe/malloc.h>
+#include <ipxe/pci.h>
+#include <ipxe/cpuid.h>
+#include <ipxe/msr.h>
+#include <ipxe/xen.h>
+#include <ipxe/xenver.h>
+#include <ipxe/xenmem.h>
+#include <ipxe/xenstore.h>
+#include <ipxe/xenbus.h>
+#include <ipxe/xengrant.h>
+#include "hvm.h"
+
+/** @file
+ *
+ * Xen HVM driver
+ *
+ */
+
+/**
+ * Get CPUID base
+ *
+ * @v hvm		HVM device
+ * @ret rc		Return status code
+ */
+static int hvm_cpuid_base ( struct hvm_device *hvm ) {
+	struct {
+		uint32_t ebx;
+		uint32_t ecx;
+		uint32_t edx;
+	} __attribute__ (( packed )) signature;
+	uint32_t base;
+	uint32_t version;
+	uint32_t discard_eax;
+	uint32_t discard_ebx;
+	uint32_t discard_ecx;
+	uint32_t discard_edx;
+
+	/* Scan for magic signature */
+	for ( base = HVM_CPUID_MIN ; base <= HVM_CPUID_MAX ;
+	      base += HVM_CPUID_STEP ) {
+		cpuid ( base, &discard_eax, &signature.ebx, &signature.ecx,
+			&signature.edx );
+		if ( memcmp ( &signature, HVM_CPUID_MAGIC,
+			      sizeof ( signature ) ) == 0 ) {
+			hvm->cpuid_base = base;
+			cpuid ( ( base + HVM_CPUID_VERSION ), &version,
+				&discard_ebx, &discard_ecx, &discard_edx );
+			DBGC2 ( hvm, "HVM using CPUID base %#08x (v%d.%d)\n",
+				base, ( version >> 16 ), ( version & 0xffff ) );
+			return 0;
+		}
+	}
+
+	DBGC ( hvm, "HVM could not find hypervisor\n" );
+	return -ENODEV;
+}
+
+/**
+ * Map hypercall page(s)
+ *
+ * @v hvm		HVM device
+ * @ret rc		Return status code
+ */
+static int hvm_map_hypercall ( struct hvm_device *hvm ) {
+	uint32_t pages;
+	uint32_t msr;
+	uint32_t discard_ecx;
+	uint32_t discard_edx;
+	physaddr_t hypercall_phys;
+	uint32_t version;
+	static xen_extraversion_t extraversion;
+	int xenrc;
+	int rc;
+
+	/* Get number of hypercall pages and MSR to use */
+	cpuid ( ( hvm->cpuid_base + HVM_CPUID_PAGES ), &pages, &msr,
+		&discard_ecx, &discard_edx );
+
+	/* Allocate pages */
+	hvm->hypercall_len = ( pages * PAGE_SIZE );
+	hvm->xen.hypercall = malloc_dma ( hvm->hypercall_len, PAGE_SIZE );
+	if ( ! hvm->xen.hypercall ) {
+		DBGC ( hvm, "HVM could not allocate %d hypercall page(s)\n",
+		       pages );
+		return -ENOMEM;
+	}
+	hypercall_phys = virt_to_phys ( hvm->xen.hypercall );
+	DBGC2 ( hvm, "HVM hypercall page(s) at [%#08lx,%#08lx) via MSR %#08x\n",
+		hypercall_phys, ( hypercall_phys + hvm->hypercall_len ), msr );
+
+	/* Write to MSR */
+	wrmsr ( msr, hypercall_phys );
+
+	/* Check that hypercall mechanism is working */
+	version = xenver_version ( &hvm->xen );
+	if ( ( xenrc = xenver_extraversion ( &hvm->xen, &extraversion ) ) != 0){
+		rc = -EXEN ( xenrc );
+		DBGC ( hvm, "HVM could not get extraversion: %s\n",
+		       strerror ( rc ) );
+		return rc;
+	}
+	DBGC2 ( hvm, "HVM found Xen version %d.%d%s\n",
+		( version >> 16 ), ( version & 0xffff ) , extraversion );
+
+	return 0;
+}
+
+/**
+ * Unmap hypercall page(s)
+ *
+ * @v hvm		HVM device
+ */
+static void hvm_unmap_hypercall ( struct hvm_device *hvm ) {
+
+	/* Free pages */
+	free_dma ( hvm->xen.hypercall, hvm->hypercall_len );
+}
+
+/**
+ * Allocate and map MMIO space
+ *
+ * @v hvm		HVM device
+ * @v space		Source mapping space
+ * @v pages		Number of pages
+ * @ret mmio		MMIO space address, or NULL on error
+ */
+static void * hvm_ioremap ( struct hvm_device *hvm, unsigned int space,
+			    unsigned int pages ) {
+	struct xen_add_to_physmap add;
+	struct xen_remove_from_physmap remove;
+	physaddr_t mmio_phys;
+	unsigned int i;
+	size_t len;
+	void *mmio;
+	int xenrc;
+	int rc;
+
+	/* Check for available space */
+	len = ( pages * PAGE_SIZE );
+	if ( ( hvm->mmio_offset + len ) > hvm->mmio_len ) {
+		DBGC ( hvm, "HVM could not allocate %zd bytes of MMIO space "
+		       "(%zd of %zd remaining)\n", len,
+		       ( hvm->mmio_len - hvm->mmio_offset ), hvm->mmio_len );
+		goto err_no_space;
+	}
+
+	/* Map this space */
+	mmio = ioremap ( ( hvm->mmio + hvm->mmio_offset ), len );
+	if ( ! mmio ) {
+		DBGC ( hvm, "HVM could not map MMIO space [%08lx,%08lx)\n",
+		       ( hvm->mmio + hvm->mmio_offset ),
+		       ( hvm->mmio + hvm->mmio_offset + len ) );
+		goto err_ioremap;
+	}
+	mmio_phys = virt_to_phys ( mmio );
+
+	/* Add to physical address space */
+	for ( i = 0 ; i < pages ; i++ ) {
+		add.domid = DOMID_SELF;
+		add.idx = i;
+		add.space = space;
+		add.gpfn = ( ( mmio_phys / PAGE_SIZE ) + i );
+		if ( ( xenrc = xenmem_add_to_physmap ( &hvm->xen, &add ) ) !=0){
+			rc = -EXEN ( xenrc );
+			DBGC ( hvm, "HVM could not add space %d idx %d at "
+			       "[%08lx,%08lx): %s\n", space, i,
+			       ( mmio_phys + ( i * PAGE_SIZE ) ),
+			       ( mmio_phys + ( ( i + 1 ) * PAGE_SIZE ) ),
+			       strerror ( rc ) );
+			goto err_add_to_physmap;
+		}
+	}
+
+	/* Update offset */
+	hvm->mmio_offset += len;
+
+	return mmio;
+
+	i = pages;
+ err_add_to_physmap:
+	for ( i-- ; ( signed int ) i >= 0 ; i-- ) {
+		remove.domid = DOMID_SELF;
+		add.gpfn = ( ( mmio_phys / PAGE_SIZE ) + i );
+		xenmem_remove_from_physmap ( &hvm->xen, &remove );
+	}
+	iounmap ( mmio );
+ err_ioremap:
+ err_no_space:
+	return NULL;
+}
+
+/**
+ * Unmap MMIO space
+ *
+ * @v hvm		HVM device
+ * @v mmio		MMIO space address
+ * @v pages		Number of pages
+ */
+static void hvm_iounmap ( struct hvm_device *hvm, void *mmio,
+			  unsigned int pages ) {
+	struct xen_remove_from_physmap remove;
+	physaddr_t mmio_phys = virt_to_phys ( mmio );
+	unsigned int i;
+	int xenrc;
+	int rc;
+
+	/* Unmap this space */
+	iounmap ( mmio );
+
+	/* Remove from physical address space */
+	for ( i = 0 ; i < pages ; i++ ) {
+		remove.domid = DOMID_SELF;
+		remove.gpfn = ( ( mmio_phys / PAGE_SIZE ) + i );
+		if ( ( xenrc = xenmem_remove_from_physmap ( &hvm->xen,
+							    &remove ) ) != 0 ) {
+			rc = -EXEN ( xenrc );
+			DBGC ( hvm, "HVM could not remove space [%08lx,%08lx): "
+			       "%s\n", ( mmio_phys + ( i * PAGE_SIZE ) ),
+			       ( mmio_phys + ( ( i + 1 ) * PAGE_SIZE ) ),
+			       strerror ( rc ) );
+			/* Nothing we can do about this */
+		}
+	}
+}
+
+/**
+ * Map shared info page
+ *
+ * @v hvm		HVM device
+ * @ret rc		Return status code
+ */
+static int hvm_map_shared_info ( struct hvm_device *hvm ) {
+	physaddr_t shared_info_phys;
+	int rc;
+
+	/* Map shared info page */
+	hvm->xen.shared = hvm_ioremap ( hvm, XENMAPSPACE_shared_info, 1 );
+	if ( ! hvm->xen.shared ) {
+		rc = -ENOMEM;
+		goto err_alloc;
+	}
+	shared_info_phys = virt_to_phys ( hvm->xen.shared );
+	DBGC2 ( hvm, "HVM shared info page at [%#08lx,%#08lx)\n",
+		shared_info_phys, ( shared_info_phys + PAGE_SIZE ) );
+
+	/* Sanity check */
+	DBGC2 ( hvm, "HVM wallclock time is %d\n",
+		readl ( &hvm->xen.shared->wc_sec ) );
+
+	return 0;
+
+	hvm_iounmap ( hvm, hvm->xen.shared, 1 );
+ err_alloc:
+	return rc;
+}
+
+/**
+ * Unmap shared info page
+ *
+ * @v hvm		HVM device
+ */
+static void hvm_unmap_shared_info ( struct hvm_device *hvm ) {
+
+	/* Unmap shared info page */
+	hvm_iounmap ( hvm, hvm->xen.shared, 1 );
+}
+
+/**
+ * Map grant table
+ *
+ * @v hvm		HVM device
+ * @ret rc		Return status code
+ */
+static int hvm_map_grant ( struct hvm_device *hvm ) {
+	struct gnttab_query_size size;
+	struct gnttab_set_version version;
+	physaddr_t grant_phys;
+	size_t len;
+	int xenrc;
+	int rc;
+
+	/* Get grant table size */
+	size.dom = DOMID_SELF;
+	if ( ( xenrc = xengrant_query_size ( &hvm->xen, &size ) ) != 0 ) {
+		rc = -EXEN ( xenrc );
+		DBGC ( hvm, "HVM could not get grant table size: %s\n",
+		       strerror ( rc ) );
+		goto err_query_size;
+	}
+	len = ( size.nr_frames * PAGE_SIZE );
+
+	/* Configure to use version 2 tables */
+	version.version = 2;
+	if ( ( xenrc = xengrant_set_version ( &hvm->xen, &version ) ) != 0 ) {
+		rc = -EXEN ( xenrc );
+		DBGC ( hvm, "HVM could not set version 2 grant table: %s\n",
+		       strerror ( rc ) );
+		goto err_set_version;
+	}
+	if ( version.version != 2 ) {
+		DBGC ( hvm, "HVM could not set version 2 grant table\n" );
+		rc = -ENOTTY;
+		goto err_set_version;
+	}
+
+	/* Map grant table */
+	hvm->xen.grant.table = hvm_ioremap ( hvm, XENMAPSPACE_grant_table,
+					     size.nr_frames );
+	if ( ! hvm->xen.grant.table ) {
+		rc = -ENODEV;
+		goto err_ioremap;
+	}
+	grant_phys = virt_to_phys ( hvm->xen.grant.table );
+	DBGC2 ( hvm, "HVM mapped grant table at [%08lx,%08lx)\n",
+		grant_phys, ( grant_phys + len ) );
+	hvm->xen.grant.count = ( len / sizeof ( hvm->xen.grant.table[0] ) );
+
+	return 0;
+
+	hvm_iounmap ( hvm, hvm->xen.grant.table, size.nr_frames );
+ err_ioremap:
+ err_set_version:
+ err_query_size:
+	return rc;
+}
+
+/**
+ * Unmap grant table
+ *
+ * @v hvm		HVM device
+ */
+static void hvm_unmap_grant ( struct hvm_device *hvm ) {
+	size_t len;
+
+	/* Unmap grant table */
+	len = ( hvm->xen.grant.count * sizeof ( hvm->xen.grant.table[0] ) );
+	hvm_iounmap ( hvm, hvm->xen.grant.table, ( len / PAGE_SIZE ) );
+}
+
+/**
+ * Map XenStore
+ *
+ * @v hvm		HVM device
+ * @ret rc		Return status code
+ */
+static int hvm_map_xenstore ( struct hvm_device *hvm ) {
+	uint64_t xenstore_evtchn;
+	uint64_t xenstore_pfn;
+	physaddr_t xenstore_phys;
+	char *name;
+	int xenrc;
+	int rc;
+
+	/* Get XenStore event channel */
+	if ( ( xenrc = xen_hvm_get_param ( &hvm->xen, HVM_PARAM_STORE_EVTCHN,
+					   &xenstore_evtchn ) ) != 0 ) {
+		rc = -EXEN ( xenrc );
+		DBGC ( hvm, "HVM could not get XenStore event channel: %s\n",
+		       strerror ( rc ) );
+		return rc;
+	}
+	hvm->xen.store.port = xenstore_evtchn;
+
+	/* Get XenStore PFN */
+	if ( ( xenrc = xen_hvm_get_param ( &hvm->xen, HVM_PARAM_STORE_PFN,
+					   &xenstore_pfn ) ) != 0 ) {
+		rc = -EXEN ( xenrc );
+		DBGC ( hvm, "HVM could not get XenStore PFN: %s\n",
+		       strerror ( rc ) );
+		return rc;
+	}
+	xenstore_phys = ( xenstore_pfn * PAGE_SIZE );
+
+	/* Map XenStore */
+	hvm->xen.store.intf = ioremap ( xenstore_phys, PAGE_SIZE );
+	if ( ! hvm->xen.store.intf ) {
+		DBGC ( hvm, "HVM could not map XenStore at [%08lx,%08lx)\n",
+		       xenstore_phys, ( xenstore_phys + PAGE_SIZE ) );
+		return -ENODEV;
+	}
+	DBGC2 ( hvm, "HVM mapped XenStore at [%08lx,%08lx) with event port "
+		"%d\n", xenstore_phys, ( xenstore_phys + PAGE_SIZE ),
+		hvm->xen.store.port );
+
+	/* Check that XenStore is working */
+	if ( ( rc = xenstore_read ( &hvm->xen, &name, "name", NULL ) ) != 0 ) {
+		DBGC ( hvm, "HVM could not read domain name: %s\n",
+		       strerror ( rc ) );
+		return rc;
+	}
+	DBGC2 ( hvm, "HVM running in domain \"%s\"\n", name );
+	free ( name );
+
+	return 0;
+}
+
+/**
+ * Unmap XenStore
+ *
+ * @v hvm		HVM device
+ */
+static void hvm_unmap_xenstore ( struct hvm_device *hvm ) {
+
+	/* Unmap XenStore */
+	iounmap ( hvm->xen.store.intf );
+}
+
+/**
+ * Probe PCI device
+ *
+ * @v pci		PCI device
+ * @ret rc		Return status code
+ */
+static int hvm_probe ( struct pci_device *pci ) {
+	struct hvm_device *hvm;
+	int rc;
+
+	/* Allocate and initialise structure */
+	hvm = zalloc ( sizeof ( *hvm ) );
+	if ( ! hvm ) {
+		rc = -ENOMEM;
+		goto err_alloc;
+	}
+	hvm->mmio = pci_bar_start ( pci, HVM_MMIO_BAR );
+	hvm->mmio_len = pci_bar_size ( pci, HVM_MMIO_BAR );
+	DBGC2 ( hvm, "HVM has MMIO space [%08lx,%08lx)\n",
+		hvm->mmio, ( hvm->mmio + hvm->mmio_len ) );
+
+	/* Fix up PCI device */
+	adjust_pci_device ( pci );
+
+	/* Attach to hypervisor */
+	if ( ( rc = hvm_cpuid_base ( hvm ) ) != 0 )
+		goto err_cpuid_base;
+	if ( ( rc = hvm_map_hypercall ( hvm ) ) != 0 )
+		goto err_map_hypercall;
+	if ( ( rc = hvm_map_shared_info ( hvm ) ) != 0 )
+		goto err_map_shared_info;
+	if ( ( rc = hvm_map_grant ( hvm ) ) != 0 )
+		goto err_map_grant;
+	if ( ( rc = hvm_map_xenstore ( hvm ) ) != 0 )
+		goto err_map_xenstore;
+
+	/* Probe Xen devices */
+	if ( ( rc = xenbus_probe ( &hvm->xen, &pci->dev ) ) != 0 ) {
+		DBGC ( hvm, "HVM could not probe Xen bus: %s\n",
+		       strerror ( rc ) );
+		goto err_xenbus_probe;
+	}
+
+	pci_set_drvdata ( pci, hvm );
+	return 0;
+
+	xenbus_remove ( &hvm->xen, &pci->dev );
+ err_xenbus_probe:
+	hvm_unmap_xenstore ( hvm );
+ err_map_xenstore:
+	hvm_unmap_grant ( hvm );
+ err_map_grant:
+	hvm_unmap_shared_info ( hvm );
+ err_map_shared_info:
+	hvm_unmap_hypercall ( hvm );
+ err_map_hypercall:
+ err_cpuid_base:
+	free ( hvm );
+ err_alloc:
+	return rc;
+}
+
+/**
+ * Remove PCI device
+ *
+ * @v pci		PCI device
+ */
+static void hvm_remove ( struct pci_device *pci ) {
+	struct hvm_device *hvm = pci_get_drvdata ( pci );
+
+	xenbus_remove ( &hvm->xen, &pci->dev );
+	hvm_unmap_xenstore ( hvm );
+	hvm_unmap_grant ( hvm );
+	hvm_unmap_shared_info ( hvm );
+	hvm_unmap_hypercall ( hvm );
+	free ( hvm );
+}
+
+/** PCI device IDs */
+static struct pci_device_id hvm_ids[] = {
+	PCI_ROM ( 0x5853, 0x0001, "hvm", "hvm", 0 ),
+};
+
+/** PCI driver */
+struct pci_driver hvm_driver __pci_driver = {
+	.ids = hvm_ids,
+	.id_count = ( sizeof ( hvm_ids ) / sizeof ( hvm_ids[0] ) ),
+	.probe = hvm_probe,
+	.remove = hvm_remove,
+};
diff --git a/src/arch/x86/drivers/xen/hvm.h b/src/arch/x86/drivers/xen/hvm.h
new file mode 100644
index 00000000..325d20d6
--- /dev/null
+++ b/src/arch/x86/drivers/xen/hvm.h
@@ -0,0 +1,75 @@
+#ifndef _HVM_H
+#define _HVM_H
+
+/** @file
+ *
+ * Xen HVM driver
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <stdint.h>
+#include <ipxe/xen.h>
+#include <xen/hvm/hvm_op.h>
+#include <xen/hvm/params.h>
+
+/** Minimum CPUID base */
+#define HVM_CPUID_MIN 0x40000000UL
+
+/** Maximum CPUID base */
+#define HVM_CPUID_MAX 0x4000ff00UL
+
+/** Increment between CPUID bases */
+#define HVM_CPUID_STEP 0x00000100UL
+
+/** Magic signature */
+#define HVM_CPUID_MAGIC "XenVMMXenVMM"
+
+/** Get Xen version */
+#define HVM_CPUID_VERSION 1
+
+/** Get number of hypercall pages */
+#define HVM_CPUID_PAGES 2
+
+/** PCI MMIO BAR */
+#define HVM_MMIO_BAR PCI_BASE_ADDRESS_1
+
+/** A Xen HVM device */
+struct hvm_device {
+	/** Xen hypervisor */
+	struct xen_hypervisor xen;
+	/** CPUID base */
+	uint32_t cpuid_base;
+	/** Length of hypercall table */
+	size_t hypercall_len;
+	/** MMIO base address */
+	unsigned long mmio;
+	/** Current offset within MMIO address space */
+	size_t mmio_offset;
+	/** Length of MMIO address space */
+	size_t mmio_len;
+};
+
+/**
+ * Get HVM parameter value
+ *
+ * @v xen		Xen hypervisor
+ * @v index		Parameter index
+ * @v value		Value to fill in
+ * @ret xenrc		Xen status code
+ */
+static inline int xen_hvm_get_param ( struct xen_hypervisor *xen,
+				      unsigned int index, uint64_t *value ) {
+	struct xen_hvm_param param;
+	int xenrc;
+
+	param.domid = DOMID_SELF;
+	param.index = index;
+	xenrc = xen_hypercall_2 ( xen, __HYPERVISOR_hvm_op, HVMOP_get_param,
+				  virt_to_phys ( &param ) );
+	*value = param.value;
+	return xenrc;
+}
+
+#endif /* _HVM_H */
diff --git a/src/arch/x86/include/bits/errfile.h b/src/arch/x86/include/bits/errfile.h
index acf8c3e3..62457562 100644
--- a/src/arch/x86/include/bits/errfile.h
+++ b/src/arch/x86/include/bits/errfile.h
@@ -45,6 +45,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
 
 #define ERRFILE_timer_rdtsc   ( ERRFILE_ARCH | ERRFILE_DRIVER | 0x00000000 )
 #define ERRFILE_timer_bios    ( ERRFILE_ARCH | ERRFILE_DRIVER | 0x00010000 )
+#define ERRFILE_hvm	      ( ERRFILE_ARCH | ERRFILE_DRIVER | 0x00020000 )
 
 #define ERRFILE_cpuid_cmd      ( ERRFILE_ARCH | ERRFILE_OTHER | 0x00000000 )
 #define ERRFILE_cpuid_settings ( ERRFILE_ARCH | ERRFILE_OTHER | 0x00010000 )
diff --git a/src/arch/x86/include/bits/xen.h b/src/arch/x86/include/bits/xen.h
new file mode 100644
index 00000000..dbccf1b7
--- /dev/null
+++ b/src/arch/x86/include/bits/xen.h
@@ -0,0 +1,164 @@
+#ifndef _BITS_XEN_H
+#define _BITS_XEN_H
+
+/** @file
+ *
+ * Xen interface
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+/* Hypercall registers */
+#ifdef __x86_64__
+#define XEN_REG1 "rdi"
+#define XEN_REG2 "rsi"
+#define XEN_REG3 "rdx"
+#define XEN_REG4 "r10"
+#define XEN_REG5 "r8"
+#else
+#define XEN_REG1 "ebx"
+#define XEN_REG2 "ecx"
+#define XEN_REG3 "edx"
+#define XEN_REG4 "esi"
+#define XEN_REG5 "edi"
+#endif
+
+/** A hypercall entry point */
+struct xen_hypercall {
+	/** Code generated by hypervisor */
+	uint8_t code[32];
+} __attribute__ (( packed ));
+
+/**
+ * Issue hypercall with one argument
+ *
+ * @v xen		Xen hypervisor
+ * @v hypercall		Hypercall number
+ * @v arg1		First argument
+ * @ret retval		Return value
+ */
+static inline __attribute__ (( always_inline )) unsigned long
+xen_hypercall_1 ( struct xen_hypervisor *xen, unsigned int hypercall,
+		  unsigned long arg1 ) {
+	register unsigned long reg1 asm ( XEN_REG1 ) = arg1;
+	unsigned long retval;
+
+	__asm__ __volatile__ ( "call *%2"
+			       : "=a" ( retval ), "+r" ( reg1 )
+			       : "r" ( &xen->hypercall[hypercall] )
+			       : XEN_REG2, XEN_REG3, XEN_REG4, XEN_REG5,
+				 "memory" );
+	return retval;
+}
+
+/**
+ * Issue hypercall with two arguments
+ *
+ * @v xen		Xen hypervisor
+ * @v hypercall		Hypercall number
+ * @v arg1		First argument
+ * @v arg2		Second argument
+ * @ret retval		Return value
+ */
+static inline __attribute__ (( always_inline )) unsigned long
+xen_hypercall_2 ( struct xen_hypervisor *xen, unsigned int hypercall,
+		  unsigned long arg1, unsigned long arg2 ) {
+	register unsigned long reg1 asm ( XEN_REG1 ) = arg1;
+	register unsigned long reg2 asm ( XEN_REG2 ) = arg2;
+	unsigned long retval;
+
+	__asm__ __volatile__ ( "call *%3"
+			       : "=a" ( retval ), "+r" ( reg1 ), "+r" ( reg2 )
+			       : "r" ( &xen->hypercall[hypercall] )
+			       : XEN_REG3, XEN_REG4, XEN_REG5, "memory" );
+	return retval;
+}
+
+/**
+ * Issue hypercall with three arguments
+ *
+ * @v xen		Xen hypervisor
+ * @v hypercall		Hypercall number
+ * @v arg1		First argument
+ * @v arg2		Second argument
+ * @v arg3		Third argument
+ * @ret retval		Return value
+ */
+static inline __attribute__ (( always_inline )) unsigned long
+xen_hypercall_3 ( struct xen_hypervisor *xen, unsigned int hypercall,
+		  unsigned long arg1, unsigned long arg2, unsigned long arg3 ) {
+	register unsigned long reg1 asm ( XEN_REG1 ) = arg1;
+	register unsigned long reg2 asm ( XEN_REG2 ) = arg2;
+	register unsigned long reg3 asm ( XEN_REG3 ) = arg3;
+	unsigned long retval;
+
+	__asm__ __volatile__ ( "call *%4"
+			       : "=a" ( retval ), "+r" ( reg1 ), "+r" ( reg2 ),
+				 "+r" ( reg3 )
+			       : "r" ( &xen->hypercall[hypercall] )
+			       : XEN_REG4, XEN_REG5, "memory" );
+	return retval;
+}
+
+/**
+ * Issue hypercall with four arguments
+ *
+ * @v xen		Xen hypervisor
+ * @v hypercall		Hypercall number
+ * @v arg1		First argument
+ * @v arg2		Second argument
+ * @v arg3		Third argument
+ * @v arg4		Fourth argument
+ * @ret retval		Return value
+ */
+static inline __attribute__ (( always_inline )) unsigned long
+xen_hypercall_4 ( struct xen_hypervisor *xen, unsigned int hypercall,
+		  unsigned long arg1, unsigned long arg2, unsigned long arg3,
+		  unsigned long arg4 ) {
+	register unsigned long reg1 asm ( XEN_REG1 ) = arg1;
+	register unsigned long reg2 asm ( XEN_REG2 ) = arg2;
+	register unsigned long reg3 asm ( XEN_REG3 ) = arg3;
+	register unsigned long reg4 asm ( XEN_REG4 ) = arg4;
+	unsigned long retval;
+
+	__asm__ __volatile__ ( "call *%5"
+			       : "=a" ( retval ), "+r" ( reg1 ), "+r" ( reg2 ),
+				 "+r" ( reg3 ), "+r" ( reg4 )
+			       : "r" ( &xen->hypercall[hypercall] )
+			       : XEN_REG5, "memory" );
+	return retval;
+}
+
+/**
+ * Issue hypercall with five arguments
+ *
+ * @v xen		Xen hypervisor
+ * @v hypercall		Hypercall number
+ * @v arg1		First argument
+ * @v arg2		Second argument
+ * @v arg3		Third argument
+ * @v arg4		Fourth argument
+ * @v arg5		Fifth argument
+ * @ret retval		Return value
+ */
+static inline __attribute__ (( always_inline )) unsigned long
+xen_hypercall_5 ( struct xen_hypervisor *xen, unsigned int hypercall,
+		  unsigned long arg1, unsigned long arg2, unsigned long arg3,
+		  unsigned long arg4, unsigned long arg5 ) {
+	register unsigned long reg1 asm ( XEN_REG1 ) = arg1;
+	register unsigned long reg2 asm ( XEN_REG2 ) = arg2;
+	register unsigned long reg3 asm ( XEN_REG3 ) = arg3;
+	register unsigned long reg4 asm ( XEN_REG4 ) = arg4;
+	register unsigned long reg5 asm ( XEN_REG5 ) = arg5;
+	unsigned long retval;
+
+	__asm__ __volatile__ ( "call *%6"
+			       : "=a" ( retval ), "+r" ( reg1 ), "+r" ( reg2 ),
+				 "+r" ( reg3 ), "+r" ( reg4 ), "+r" ( reg5 )
+			       : "r" ( &xen->hypercall[hypercall] )
+			       : "memory" );
+	return retval;
+}
+
+#endif /* _BITS_XEN_H */