lguest: the guest code
lguest is a simple hypervisor for Linux on Linux. Unlike kvm it doesn't need
VT/SVM hardware. Unlike Xen it's simply "modprobe and go". Unlike both, it's
5000 lines and self-contained.
Performance is ok, but not great (-30% on kernel compile). But given its
hackability, I expect this to improve, along with the paravirt_ops code which
it supplies a complete example for. There's also a 64-bit version being
worked on and other craziness.
But most of all, lguest is awesome fun! Too much of the kernel is a big ball
of hair. lguest is simple enough to dive into and hack, plus has some warts
which scream "fork me!".
This patch:
This is the code and headers required to make an i386 kernel an lguest guest.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andi Kleen <ak@suse.de>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/lguest.h b/include/linux/lguest.h
new file mode 100644
index 0000000..f30c04f
--- /dev/null
+++ b/include/linux/lguest.h
@@ -0,0 +1,85 @@
+/* Things the lguest guest needs to know. Note: like all lguest interfaces,
+ * this is subject to wild and random change between versions. */
+#ifndef _ASM_LGUEST_H
+#define _ASM_LGUEST_H
+
+/* These are randomly chosen numbers which indicate we're an lguest at boot */
+#define LGUEST_MAGIC_EBP 0x4C687970
+#define LGUEST_MAGIC_EDI 0x652D4D65
+#define LGUEST_MAGIC_ESI 0xFFFFFFFF
+
+#ifndef __ASSEMBLY__
+#include <asm/irq.h>
+
+#define LHCALL_FLUSH_ASYNC 0
+#define LHCALL_LGUEST_INIT 1
+#define LHCALL_CRASH 2
+#define LHCALL_LOAD_GDT 3
+#define LHCALL_NEW_PGTABLE 4
+#define LHCALL_FLUSH_TLB 5
+#define LHCALL_LOAD_IDT_ENTRY 6
+#define LHCALL_SET_STACK 7
+#define LHCALL_TS 8
+#define LHCALL_TIMER_READ 9
+#define LHCALL_HALT 10
+#define LHCALL_GET_WALLCLOCK 11
+#define LHCALL_BIND_DMA 12
+#define LHCALL_SEND_DMA 13
+#define LHCALL_SET_PTE 14
+#define LHCALL_SET_PMD 15
+#define LHCALL_LOAD_TLS 16
+
+#define LGUEST_TRAP_ENTRY 0x1F
+
+static inline unsigned long
+hcall(unsigned long call,
+ unsigned long arg1, unsigned long arg2, unsigned long arg3)
+{
+ asm volatile("int $" __stringify(LGUEST_TRAP_ENTRY)
+ : "=a"(call)
+ : "a"(call), "d"(arg1), "b"(arg2), "c"(arg3)
+ : "memory");
+ return call;
+}
+
+void async_hcall(unsigned long call,
+ unsigned long arg1, unsigned long arg2, unsigned long arg3);
+
+/* Can't use our min() macro here: needs to be a constant */
+#define LGUEST_IRQS (NR_IRQS < 32 ? NR_IRQS: 32)
+
+#define LHCALL_RING_SIZE 64
+struct hcall_ring
+{
+ u32 eax, edx, ebx, ecx;
+};
+
+/* All the good stuff happens here: guest registers it with LGUEST_INIT */
+struct lguest_data
+{
+/* Fields which change during running: */
+ /* 512 == enabled (same as eflags) */
+ unsigned int irq_enabled;
+ /* Interrupts blocked by guest. */
+ DECLARE_BITMAP(blocked_interrupts, LGUEST_IRQS);
+
+ /* Virtual address of page fault. */
+ unsigned long cr2;
+
+ /* Async hypercall ring. 0xFF == done, 0 == pending. */
+ u8 hcall_status[LHCALL_RING_SIZE];
+ struct hcall_ring hcalls[LHCALL_RING_SIZE];
+
+/* Fields initialized by the hypervisor at boot: */
+ /* Memory not to try to access */
+ unsigned long reserve_mem;
+ /* ID of this guest (used by network driver to set ethernet address) */
+ u16 guestid;
+
+/* Fields initialized by the guest at boot: */
+ /* Instruction range to suppress interrupts even if enabled */
+ unsigned long noirq_start, noirq_end;
+};
+extern struct lguest_data lguest_data;
+#endif /* __ASSEMBLY__ */
+#endif /* _ASM_LGUEST_H */