[PATCH 3/7] More generic paravirtualization entry point.

Chris Wright
2006-10-29T02:45:05Z

[-- Attachment #1: 011-paravirt-head.S.patch --]
[-- Type: text/plain, Size: 3420 bytes --]

1) Each hypervisor writes a probe function to detect whether we are
running under that hypervisor. paravirt_probe() registers this
function.

2) If vmlinux is booted with ring != 0, we call all the probe
functions (with registers except %esp intact) in link order: the
winner will not return.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Zachary Amsden <zach@vmware.com>

---
arch/i386/kernel/Makefile | 2 ++
arch/i386/kernel/head.S | 33 +++++++++++++++++++++++++++++++++
arch/i386/kernel/paravirt.c | 6 +++++-
arch/i386/kernel/vmlinux.lds.S | 6 ++++++
include/asm-i386/paravirt.h | 5 +++++
5 files changed, 51 insertions(+), 1 deletion(-)

--- linux-2.6-pv.orig/arch/i386/kernel/Makefile
+++ linux-2.6-pv/arch/i386/kernel/Makefile
@@ -39,6 +39,8 @@ obj-$(CONFIG_VM86) += vm86.o
obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
obj-$(CONFIG_HPET_TIMER) += hpet.o
obj-$(CONFIG_K8_NB) += k8.o
+
+# Make sure this is linked after any other paravirt_ops structs: see head.S
obj-$(CONFIG_PARAVIRT) += paravirt.o

EXTRA_AFLAGS := -traditional
--- linux-2.6-pv.orig/arch/i386/kernel/head.S
+++ linux-2.6-pv/arch/i386/kernel/head.S
@@ -55,6 +55,12 @@
*/
ENTRY(startup_32)

+#ifdef CONFIG_PARAVIRT
+ movl %cs, %eax
+ testl $0x3, %eax
+ jnz startup_paravirt
+#endif
+
/*
* Set segments to known values.
*/
@@ -486,6 +492,33 @@ ignore_int:
#endif
iret

+#ifdef CONFIG_PARAVIRT
+startup_paravirt:
+ cld
+ movl $(init_thread_union+THREAD_SIZE),%esp
+
+ /* We take pains to preserve all the regs. */
+ pushl %edx
+ pushl %ecx
+ pushl %eax
+
+ /* paravirt.o is last in link, and that probe fn never returns */
+ pushl $__start_paravirtprobe
+1:
+ movl 0(%esp), %eax
+ pushl (%eax)
+ movl 8(%esp), %eax
+ call *(%esp)
+ popl %eax
+
+ movl 4(%esp), %eax
+ movl 8(%esp), %ecx
+ movl 12(%esp), %edx
+
+ addl $4, (%esp)
+ jmp 1b
+#endif
+
/*
* Real beginning of normal "text" segment
*/
--- linux-2.6-pv.orig/arch/i386/kernel/paravirt.c
+++ linux-2.6-pv/arch/i386/kernel/paravirt.c
@@ -392,7 +392,11 @@ static int __init print_banner(void)
return 0;
}
core_initcall(print_banner);
-
+
+/* We simply declare start_kernel to be the paravirt probe of last resort. */
+asmlinkage void __init start_kernel(void);
+paravirt_probe(start_kernel);
+
struct paravirt_ops paravirt_ops = {
.name = "bare hardware",
.paravirt_enabled = 0,
--- linux-2.6-pv.orig/arch/i386/kernel/vmlinux.lds.S
+++ linux-2.6-pv/arch/i386/kernel/vmlinux.lds.S
@@ -60,6 +60,12 @@ SECTIONS
CONSTRUCTORS
} :data

+ __start_paravirtprobe = .;
+ .paravirtprobe : AT(ADDR(.paravirtprobe) - LOAD_OFFSET) {
+ *(.paravirtprobe)
+ }
+ __stop_paravirtprobe = .;
+
. = ALIGN(4096);
__nosave_begin = .;
.data_nosave : AT(ADDR(.data_nosave) - LOAD_OFFSET) { *(.data.nosave) }
--- linux-2.6-pv.orig/include/asm-i386/paravirt.h
+++ linux-2.6-pv/include/asm-i386/paravirt.h
@@ -120,6 +120,11 @@ struct paravirt_ops
void (fastcall *iret)(void);
};

+/* Mark a paravirt probe function. */
+#define paravirt_probe(fn) \
+ static void (*__paravirtprobe_##fn)(void) __attribute_used__ \
+ __attribute__((__section__(".paravirtprobe"))) = fn
+
extern struct paravirt_ops paravirt_ops;

#define paravirt_enabled() (paravirt_ops.paravirt_enabled)

--