s390/uv: introduce guest side ultravisor code

The Ultravisor Call Facility (stfle bit 158) defines an API to the
Ultravisor (UV calls), a mini hypervisor located at machine
level. With help of the Ultravisor, KVM will be able to run
"protected" VMs, special VMs whose memory and management data are
unavailable to KVM.

The protected VMs can also request services from the Ultravisor.
The guest api consists of UV calls to share and unshare memory with the
kvm hypervisor.

To enable this feature support PROTECTED_VIRTUALIZATION_GUEST kconfig
option has been introduced.
Co-developed-by: Janosch Frank <frankja@de.ibm.com>
Signed-off-by: Janosch Frank <frankja@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/Kconfig

@@ -837,6 +837,17 @@ config HAVE_PNETID
 
 menu "Virtualization"
 
+config PROTECTED_VIRTUALIZATION_GUEST
+	def_bool n
+	prompt "Protected virtualization guest support"
+	help
+	  Select this option, if you want to be able to run this
+	  kernel as a protected virtualization KVM guest.
+	  Protected virtualization capable machines have a mini hypervisor
+	  located at machine level (an ultravisor). With help of the
+	  Ultravisor, KVM will be able to run "protected" VMs, special
+	  VMs whose memory and management data are unavailable to KVM.
+
 config PFAULT
 	def_bool y
 	prompt "Pseudo page fault support"

arch/s390/boot/Makefile

@@ -30,6 +30,7 @@ CFLAGS_sclp_early_core.o += -I$(srctree)/drivers/s390/char
 
 obj-y	:= head.o als.o startup.o mem_detect.o ipl_parm.o string.o ebcdic.o
 obj-y	+= sclp_early_core.o mem.o ipl_vmparm.o cmdline.o ctype.o
+obj-$(CONFIG_PROTECTED_VIRTUALIZATION_GUEST)	+= uv.o
 targets	:= bzImage startup.a section_cmp.boot.data section_cmp.boot.preserved.data $(obj-y)
 subdir-	:= compressed
 

arch/s390/boot/startup.c

@@ -2,6 +2,7 @@
 #include <linux/string.h>
 #include <asm/setup.h>
 #include <asm/sclp.h>
+#include <asm/uv.h>
 #include "compressed/decompressor.h"
 #include "boot.h"
 
@@ -53,6 +54,7 @@ void startup_kernel(void)
 {
 	void *img;
 
+	uv_query_info();
 	rescue_initrd();
 	sclp_early_read_info();
 	store_ipl_parmblock();

arch/s390/boot/uv.c

+// SPDX-License-Identifier: GPL-2.0
+#include <asm/uv.h>
+#include <asm/facility.h>
+#include <asm/sections.h>
+
+int __bootdata_preserved(prot_virt_guest);
+
+void uv_query_info(void)
+{
+	struct uv_cb_qui uvcb = {
+		.header.cmd = UVC_CMD_QUI,
+		.header.len = sizeof(uvcb)
+	};
+
+	if (!test_facility(158))
+		return;
+
+	if (uv_call(0, (uint64_t)&uvcb))
+		return;
+
+	if (test_bit_inv(BIT_UVC_CMD_SET_SHARED_ACCESS, (unsigned long *)uvcb.inst_calls_list) &&
+	    test_bit_inv(BIT_UVC_CMD_REMOVE_SHARED_ACCESS, (unsigned long *)uvcb.inst_calls_list))
+		prot_virt_guest = 1;
+}

arch/s390/include/asm/uv.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Ultravisor Interfaces
+ *
+ * Copyright IBM Corp. 2019
+ *
+ * Author(s):
+ *	Vasily Gorbik <gor@linux.ibm.com>
+ *	Janosch Frank <frankja@linux.ibm.com>
+ */
+#ifndef _ASM_S390_UV_H
+#define _ASM_S390_UV_H
+
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/bug.h>
+#include <asm/page.h>
+
+#define UVC_RC_EXECUTED		0x0001
+#define UVC_RC_INV_CMD		0x0002
+#define UVC_RC_INV_STATE	0x0003
+#define UVC_RC_INV_LEN		0x0005
+#define UVC_RC_NO_RESUME	0x0007
+
+#define UVC_CMD_QUI			0x0001
+#define UVC_CMD_SET_SHARED_ACCESS	0x1000
+#define UVC_CMD_REMOVE_SHARED_ACCESS	0x1001
+
+/* Bits in installed uv calls */
+enum uv_cmds_inst {
+	BIT_UVC_CMD_QUI = 0,
+	BIT_UVC_CMD_SET_SHARED_ACCESS = 8,
+	BIT_UVC_CMD_REMOVE_SHARED_ACCESS = 9,
+};
+
+struct uv_cb_header {
+	u16 len;
+	u16 cmd;	/* Command Code */
+	u16 rc;		/* Response Code */
+	u16 rrc;	/* Return Reason Code */
+} __packed __aligned(8);
+
+struct uv_cb_qui {
+	struct uv_cb_header header;
+	u64 reserved08;
+	u64 inst_calls_list[4];
+	u64 reserved30[15];
+} __packed __aligned(8);
+
+struct uv_cb_share {
+	struct uv_cb_header header;
+	u64 reserved08[3];
+	u64 paddr;
+	u64 reserved28;
+} __packed __aligned(8);
+
+static inline int uv_call(unsigned long r1, unsigned long r2)
+{
+	int cc;
+
+	asm volatile(
+		"0:	.insn rrf,0xB9A40000,%[r1],%[r2],0,0\n"
+		"		brc	3,0b\n"
+		"		ipm	%[cc]\n"
+		"		srl	%[cc],28\n"
+		: [cc] "=d" (cc)
+		: [r1] "a" (r1), [r2] "a" (r2)
+		: "memory", "cc");
+	return cc;
+}
+
+#ifdef CONFIG_PROTECTED_VIRTUALIZATION_GUEST
+extern int prot_virt_guest;
+
+static inline int is_prot_virt_guest(void)
+{
+	return prot_virt_guest;
+}
+
+static inline int share(unsigned long addr, u16 cmd)
+{
+	struct uv_cb_share uvcb = {
+		.header.cmd = cmd,
+		.header.len = sizeof(uvcb),
+		.paddr = addr
+	};
+
+	if (!is_prot_virt_guest())
+		return -ENOTSUPP;
+	/*
+	 * Sharing is page wise, if we encounter addresses that are
+	 * not page aligned, we assume something went wrong. If
+	 * malloced structs are passed to this function, we could leak
+	 * data to the hypervisor.
+	 */
+	BUG_ON(addr & ~PAGE_MASK);
+
+	if (!uv_call(0, (u64)&uvcb))
+		return 0;
+	return -EINVAL;
+}
+
+/*
+ * Guest 2 request to the Ultravisor to make a page shared with the
+ * hypervisor for IO.
+ *
+ * @addr: Real or absolute address of the page to be shared
+ */
+static inline int uv_set_shared(unsigned long addr)
+{
+	return share(addr, UVC_CMD_SET_SHARED_ACCESS);
+}
+
+/*
+ * Guest 2 request to the Ultravisor to make a page unshared.
+ *
+ * @addr: Real or absolute address of the page to be unshared
+ */
+static inline int uv_remove_shared(unsigned long addr)
+{
+	return share(addr, UVC_CMD_REMOVE_SHARED_ACCESS);
+}
+
+void uv_query_info(void);
+#else
+#define is_prot_virt_guest() 0
+static inline int uv_set_shared(unsigned long addr) { return 0; }
+static inline int uv_remove_shared(unsigned long addr) { return 0; }
+static inline void uv_query_info(void) {}
+#endif
+
+#endif /* _ASM_S390_UV_H */

arch/s390/kernel/setup.c

@@ -70,6 +70,7 @@
 #include <asm/alternative.h>
 #include <asm/nospec-branch.h>
 #include <asm/mem_detect.h>
+#include <asm/uv.h>
 #include "entry.h"
 
 /*
@@ -89,6 +90,10 @@ char elf_platform[ELF_PLATFORM_SIZE];
 
 unsigned long int_hwcap = 0;
 
+#ifdef CONFIG_PROTECTED_VIRTUALIZATION_GUEST
+int __bootdata_preserved(prot_virt_guest);
+#endif
+
 int __bootdata(noexec_disabled);
 int __bootdata(memory_end_set);
 unsigned long __bootdata(memory_end);