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authorAl Viro <viro@zeniv.linux.org.uk>2008-08-18 05:05:42 +0400
committerH. Peter Anvin <hpa@zytor.com>2008-10-23 09:55:20 +0400
commitbb8985586b7a906e116db835c64773b7a7d51663 (patch)
treede93ae58e88cc563d95cc124a73f3930594c6100 /arch/x86/include/asm/pvclock-abi.h
parent8ede0bdb63305d3353efd97e9af6210afb05734e (diff)
downloadlinux-bb8985586b7a906e116db835c64773b7a7d51663.tar.xz
x86, um: ... and asm-x86 move
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'arch/x86/include/asm/pvclock-abi.h')
-rw-r--r--arch/x86/include/asm/pvclock-abi.h42
1 files changed, 42 insertions, 0 deletions
diff --git a/arch/x86/include/asm/pvclock-abi.h b/arch/x86/include/asm/pvclock-abi.h
new file mode 100644
index 000000000000..edb3b4ecfc81
--- /dev/null
+++ b/arch/x86/include/asm/pvclock-abi.h
@@ -0,0 +1,42 @@
+#ifndef ASM_X86__PVCLOCK_ABI_H
+#define ASM_X86__PVCLOCK_ABI_H
+#ifndef __ASSEMBLY__
+
+/*
+ * These structs MUST NOT be changed.
+ * They are the ABI between hypervisor and guest OS.
+ * Both Xen and KVM are using this.
+ *
+ * pvclock_vcpu_time_info holds the system time and the tsc timestamp
+ * of the last update. So the guest can use the tsc delta to get a
+ * more precise system time. There is one per virtual cpu.
+ *
+ * pvclock_wall_clock references the point in time when the system
+ * time was zero (usually boot time), thus the guest calculates the
+ * current wall clock by adding the system time.
+ *
+ * Protocol for the "version" fields is: hypervisor raises it (making
+ * it uneven) before it starts updating the fields and raises it again
+ * (making it even) when it is done. Thus the guest can make sure the
+ * time values it got are consistent by checking the version before
+ * and after reading them.
+ */
+
+struct pvclock_vcpu_time_info {
+ u32 version;
+ u32 pad0;
+ u64 tsc_timestamp;
+ u64 system_time;
+ u32 tsc_to_system_mul;
+ s8 tsc_shift;
+ u8 pad[3];
+} __attribute__((__packed__)); /* 32 bytes */
+
+struct pvclock_wall_clock {
+ u32 version;
+ u32 sec;
+ u32 nsec;
+} __attribute__((__packed__));
+
+#endif /* __ASSEMBLY__ */
+#endif /* ASM_X86__PVCLOCK_ABI_H */