[PATCH v2 4/9] xen/pvh: Bootstrap PVH guest

[Boris Ostrovsky]

Start PVH guest at XEN_ELFNOTE_PHYS32_ENTRY address. Setup hypercall
page, initialize boot_params, enable early page tables.

Since this stub is executed before kernel entry point we cannot use
variables in .bss which is cleared by kernel. We explicitly place
variables that are initialized here into .data.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
Changes in v2:
* Assembly cleanup
* Check for e820 size in init_pvh_bootparams()
* Check XEN_HVM_START_MAGIC_VALUE in start_info


 arch/x86/xen/Kconfig     |   2 +-
 arch/x86/xen/Makefile    |   1 +
 arch/x86/xen/enlighten.c |  98 ++++++++++++++++++++++++++++++++-
 arch/x86/xen/xen-pvh.S   | 137 +++++++++++++++++++++++++++++++++++++++++++++++
 include/xen/xen.h        |   5 ++
 5 files changed, 241 insertions(+), 2 deletions(-)
 create mode 100644 arch/x86/xen/xen-pvh.S

diff --git a/arch/x86/xen/Kconfig b/arch/x86/xen/Kconfig
index c7b15f3..76b6dbd 100644
--- a/arch/x86/xen/Kconfig
+++ b/arch/x86/xen/Kconfig
@@ -53,5 +53,5 @@ config XEN_DEBUG_FS
 
 config XEN_PVH
 	bool "Support for running as a PVH guest"
-	depends on X86_64 && XEN && XEN_PVHVM
+	depends on XEN && XEN_PVHVM && ACPI
 	def_bool n
diff --git a/arch/x86/xen/Makefile b/arch/x86/xen/Makefile
index e47e527..cb0164a 100644
--- a/arch/x86/xen/Makefile
+++ b/arch/x86/xen/Makefile
@@ -23,3 +23,4 @@ obj-$(CONFIG_XEN_DEBUG_FS)	+= debugfs.o
 obj-$(CONFIG_XEN_DOM0)		+= vga.o
 obj-$(CONFIG_SWIOTLB_XEN)	+= pci-swiotlb-xen.o
 obj-$(CONFIG_XEN_EFI)		+= efi.o
+obj-$(CONFIG_XEN_PVH)	 	+= xen-pvh.o
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 828f1b2..c82fe14 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -45,6 +45,7 @@
 #include <xen/interface/memory.h>
 #include <xen/interface/nmi.h>
 #include <xen/interface/xen-mca.h>
+#include <xen/interface/hvm/start_info.h>
 #include <xen/features.h>
 #include <xen/page.h>
 #include <xen/hvm.h>
@@ -121,7 +122,8 @@
 DEFINE_PER_CPU(uint32_t, xen_vcpu_id);
 EXPORT_PER_CPU_SYMBOL(xen_vcpu_id);
 
-enum xen_domain_type xen_domain_type = XEN_NATIVE;
+enum xen_domain_type xen_domain_type
+	__attribute__((section(".data"))) = XEN_NATIVE;
 EXPORT_SYMBOL_GPL(xen_domain_type);
 
 unsigned long *machine_to_phys_mapping = (void *)MACH2PHYS_VIRT_START;
@@ -176,6 +178,17 @@ struct tls_descs {
  */
 static DEFINE_PER_CPU(struct tls_descs, shadow_tls_desc);
 
+#ifdef CONFIG_XEN_PVH
+/*
+ * PVH variables. These need to live in data segment since they are
+ * initialized before startup_{32|64}, which clear .bss, are invoked.
+ */
+bool xen_pvh __attribute__((section(".data"))) = 0;
+struct hvm_start_info pvh_start_info __attribute__((section(".data")));
+unsigned int pvh_start_info_sz = sizeof(pvh_start_info);
+struct boot_params pvh_bootparams __attribute__((section(".data")));
+#endif
+
 static void clamp_max_cpus(void)
 {
 #ifdef CONFIG_SMP
@@ -1656,6 +1669,89 @@ asmlinkage __visible void __init xen_start_kernel(void)
 #endif
 }
 
+#ifdef CONFIG_XEN_PVH
+static void __init init_pvh_bootparams(void)
+{
+	struct xen_memory_map memmap;
+	unsigned int i;
+	int rc;
+
+	memset(&pvh_bootparams, 0, sizeof(pvh_bootparams));
+
+	memmap.nr_entries = ARRAY_SIZE(pvh_bootparams.e820_map);
+	set_xen_guest_handle(memmap.buffer, pvh_bootparams.e820_map);
+	rc = HYPERVISOR_memory_op(XENMEM_memory_map, &memmap);
+	if (rc) {
+		xen_raw_printk("XENMEM_memory_map failed (%d)\n", rc);
+		BUG();
+	}
+
+	if (memmap.nr_entries < E820MAX) {
+		pvh_bootparams.e820_map[memmap.nr_entries].addr =
+			ISA_START_ADDRESS;
+		pvh_bootparams.e820_map[memmap.nr_entries].size =
+			ISA_END_ADDRESS - ISA_START_ADDRESS;
+		pvh_bootparams.e820_map[memmap.nr_entries++].type =
+			E820_RESERVED;
+	} else
+		xen_raw_printk("Warning: Can fit ISA range into e820\n");
+
+	sanitize_e820_map(pvh_bootparams.e820_map,
+			  ARRAY_SIZE(pvh_bootparams.e820_map),
+			  &memmap.nr_entries);
+
+	pvh_bootparams.e820_entries = memmap.nr_entries;
+	for (i = 0; i < pvh_bootparams.e820_entries; i++)
+		e820_add_region(pvh_bootparams.e820_map[i].addr,
+				pvh_bootparams.e820_map[i].size,
+				pvh_bootparams.e820_map[i].type);
+
+	pvh_bootparams.hdr.cmd_line_ptr =
+		pvh_start_info.cmdline_paddr;
+
+	/* The first module is always ramdisk. */
+	if (pvh_start_info.nr_modules) {
+		struct hvm_modlist_entry *modaddr =
+			__va(pvh_start_info.modlist_paddr);
+		pvh_bootparams.hdr.ramdisk_image = modaddr->paddr;
+		pvh_bootparams.hdr.ramdisk_size = modaddr->size;
+	}
+
+	/*
+	 * See Documentation/x86/boot.txt.
+	 *
+	 * Version 2.12 supports Xen entry point but we will use default x86/PC
+	 * environment (i.e. hardware_subarch 0).
+	 */
+	pvh_bootparams.hdr.version = 0x212;
+	pvh_bootparams.hdr.type_of_loader = (9 << 4) | 0; /* Xen loader */
+}
+
+/*
+ * This routine (and those that it might call) should not use
+ * anything that lives in .bss since that segment will be cleared later.
+ */
+void __init xen_prepare_pvh(void)
+{
+	u32 msr;
+	u64 pfn;
+
+	if (pvh_start_info.magic != XEN_HVM_START_MAGIC_VALUE) {
+		xen_raw_printk("Error: Unexpected magic value (0x%08x)\n",
+				pvh_start_info.magic);
+		BUG();
+	}
+
+	xen_pvh = 1;
+
+	msr = cpuid_ebx(xen_cpuid_base() + 2);
+	pfn = __pa(hypercall_page);
+	wrmsr_safe(msr, (u32)pfn, (u32)(pfn >> 32));
+
+	init_pvh_bootparams();
+}
+#endif
+
 void __ref xen_hvm_init_shared_info(void)
 {
 	int cpu;
diff --git a/arch/x86/xen/xen-pvh.S b/arch/x86/xen/xen-pvh.S
new file mode 100644
index 0000000..410036a
--- /dev/null
+++ b/arch/x86/xen/xen-pvh.S
@@ -0,0 +1,137 @@
+/*
+ * Copyright C 2016, Oracle and/or its affiliates. All rights reserved.
+ *
+ * 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, see <http://www.gnu.org/licenses/>.
+ */
+
+	.code32
+	.text
+#define _pa(x)          ((x) - __START_KERNEL_map)
+
+#include <linux/elfnote.h>
+#include <linux/init.h>
+#include <linux/linkage.h>
+#include <asm/segment.h>
+#include <asm/asm.h>
+#include <asm/boot.h>
+#include <asm/processor-flags.h>
+#include <asm/msr.h>
+#include <xen/interface/elfnote.h>
+
+	__HEAD
+
+/* Entry point for PVH guests. */
+ENTRY(pvh_start_xen)
+	cld
+
+	lgdt (_pa(gdt))
+
+	mov $(__BOOT_DS),%eax
+	mov %eax,%ds
+	mov %eax,%es
+	mov %eax,%ss
+
+	/* Stash hvm_start_info. */
+	mov $_pa(pvh_start_info), %edi
+	mov %ebx, %esi
+	mov _pa(pvh_start_info_sz), %ecx
+	shr $2,%ecx
+	rep
+	movsl
+
+	mov $_pa(early_stack_end), %esp
+
+	/* Enable PAE mode. */
+	mov %cr4, %eax
+	orl $X86_CR4_PAE, %eax
+	mov %eax, %cr4
+
+#ifdef CONFIG_X86_64
+	/* Enable Long mode. */
+	mov $MSR_EFER, %ecx
+	rdmsr
+	btsl $_EFER_LME, %eax
+	wrmsr
+
+	/* Enable pre-constructed page tables. */
+	mov $_pa(init_level4_pgt), %eax
+	mov %eax, %cr3
+	mov $(X86_CR0_PG | X86_CR0_PE), %eax
+	mov %eax, %cr0
+
+	/* Jump to 64-bit mode. */
+        ljmp $__KERNEL_CS, $_pa(1f)
+
+	/* 64-bit entry point. */
+	.code64
+1:
+	call xen_prepare_pvh
+
+	/* startup_64 expects boot_params in %rsi. */
+	mov $_pa(pvh_bootparams), %rsi
+	mov $_pa(startup_64), %rax
+	jmp *%rax
+
+#else /* CONFIG_X86_64 */
+
+	call mk_early_pgtbl_32
+
+	mov $_pa(initial_page_table), %eax
+	mov %eax, %cr3
+
+	mov %cr0, %eax
+	or $(X86_CR0_PG | X86_CR0_PE), %eax
+	mov %eax, %cr0
+
+	ljmp $__BOOT_CS, $1f
+1:
+	call xen_prepare_pvh
+	mov $_pa(pvh_bootparams), %esi
+
+	/* startup_32 doesn't expect paging and PAE to be on. */
+	ljmp $__BOOT_CS, $_pa(2f)
+2:
+	mov %cr0, %eax
+	and $~X86_CR0_PG, %eax
+	mov %eax, %cr0
+	mov %cr4, %eax
+	and $~X86_CR4_PAE, %eax
+	mov %eax, %cr4
+
+	ljmp    $0x10, $_pa(startup_32)
+#endif
+ENDPROC(pvh_start_xen)
+
+	.data
+gdt:
+	.word	gdt_end - gdt
+	.long	_pa(gdt)
+	.word	0
+	.quad	0x0000000000000000 /* NULL descriptor */
+#ifdef CONFIG_X86_64
+	.quad	0x00af9a000000ffff /* __KERNEL_CS */
+#else
+	.quad	0x00cf9a000000ffff /* __KERNEL_CS */
+#endif
+	.quad	0x00cf92000000ffff /* __KERNEL_DS */
+gdt_end:
+
+	.bss
+	.balign 4
+early_stack:
+	.fill 16, 1, 0
+early_stack_end:
+
+	ELFNOTE(Xen, XEN_ELFNOTE_PHYS32_ENTRY,
+	             _ASM_PTR (pvh_start_xen - __START_KERNEL_map))
diff --git a/include/xen/xen.h b/include/xen/xen.h
index d0f9684..6e8b7fc 100644
--- a/include/xen/xen.h
+++ b/include/xen/xen.h
@@ -29,6 +29,11 @@ enum xen_domain_type {
 #define xen_initial_domain()	(0)
 #endif	/* CONFIG_XEN_DOM0 */
 
+#ifdef CONFIG_XEN_PVH
+extern bool xen_pvh;
+#define xen_pvh_domain()	(xen_hvm_domain() && xen_pvh)
+#else
 #define xen_pvh_domain()	(0)
+#endif
 
 #endif	/* _XEN_XEN_H */
-- 
1.8.3.1